Photovoltaic micro-grid and water collection irrigation collaborative energy supply scheduling control method

Abstract

The application relates to the technical field of distributed energy scheduling, and discloses a photovoltaic microgrid and water collection and irrigation cooperative energy scheduling control method, which comprises the following steps: collecting real-time voltage, photovoltaic power and water level data of a direct-current bus, calculating a bus voltage transient fluctuation rate, determining a frequency adjustment compensation amount according to voltage drop depth when the fluctuation rate exceeds a safety threshold, reducing the operating frequency of a frequency conversion driver, and generating a load-side active power unloading amount by using a cubic proportional relationship between the shaft power of a centrifugal water pump and the operating frequency. The power unloading amount generated by the physical characteristics of the load side is used to offset the power shortage during the power climbing response delay of the electrochemical energy storage power, the direct-current bus transient voltage drop is inhibited, the transient stability of the independent microgrid system under extreme working conditions is improved, and the dependence on large-capacity energy storage configuration is reduced.

Description

Technical Field

[0001] This invention relates to a method for coordinated energy supply scheduling and control of photovoltaic microgrids and water collection irrigation, belonging to the field of distributed energy scheduling technology. Background Technology

[0002] Currently, independent photovoltaic microgrids equipped with energy storage units are widely used in remote areas for water collection and irrigation. The system collects power from the photovoltaic array through a DC bus to drive variable frequency centrifugal water pumps. In this type of islanded power supply mode, maintaining the transient stability of the DC bus voltage is the key to ensuring the continuous operation of the system. Conventional scheduling schemes issue operating instructions based on long-term water demand and rely on energy storage units to smooth power fluctuations caused by environmental disturbances in order to maintain the active power balance of the DC bus. As a high-power mechanical load, the centrifugal water pump has a shaft power that is proportional to the cube of the motor drive frequency. Small frequency fluctuations can cause drastic changes in the power demand on the load side. However, existing microgrid control logic usually treats the water pump as a passive power consumption node and fails to transform the mechanical rotational inertia of the water collection system and the fluid characteristics of the pipeline network into regulation resources on the grid side.

[0003] When photovoltaic (PV) output power experiences millisecond-level transient drops due to meteorological factors, electrochemical energy storage systems, constrained by electrochemical reaction rates and converter power ramp-up limitations, exhibit a physical hysteresis of 100ms to 200ms in their response. Within this timeframe, if PV output drops sharply while the load side maintains rated power operation, the system will experience a transient power deficit, causing the DC bus voltage to drop rapidly and exceed the safety lower limit. To avoid system shutdowns caused by voltage collapse, the industry typically employs redundant design schemes that multiply the capacity of energy storage batteries. However, this increases construction costs and does not resolve the mismatch in response time scales between the source and load sides from a control mechanism perspective. Furthermore, there is a redundancy burden at the hardware level, and existing software control and scheduling logic... The collaborative processing of dynamic response of source and load also has shortcomings. For example, Chinese invention patent application CN118523355A discloses a double-layer MPC virtual inertia control method and system for full-power variable speed pumped storage units. This technology attempts to suppress photovoltaic fluctuations and take into account speed recovery through model predictive control algorithms. However, in the case of water collection and irrigation in remote areas, such control strategies that rely heavily on the accurate mathematical model of the system face the problem of excessive computational load and insufficient exploration of nonlinear fluid load characteristics. The above logic focuses on supporting the grid frequency and is difficult to directly cope with the voltage drop of the microgrid DC bus in the energy storage ramp-up lag window. It does not consider physical boundary constraints such as water hammer effect of fluid system, which can cause mechanical damage.

[0004] Therefore, how to utilize the power nonlinearity characteristics of hydraulic load to achieve transient balance of the DC bus of the microgrid and reduce the dependence on large-capacity energy storage configuration has become the technical problem to be solved by this invention. Summary of the Invention

[0005] To address the problems in the background art, the technical solution of the present invention is as follows: A method for coordinated energy supply scheduling and control of photovoltaic microgrids and water collection irrigation, comprising the following steps: Step S1: Collect the real-time DC bus voltage, real-time output power of the photovoltaic array, and real-time water level of the water collection tank of the independent microgrid system. Step S2: Calculate the first derivative of the real-time DC bus voltage with respect to time to obtain the transient fluctuation rate of the bus voltage; Step S3: Compare the transient fluctuation rate of the bus voltage with the preset voltage drop safety threshold. The voltage drop safety threshold is determined based on the power ramp-up response hysteresis time of the electrochemical energy storage unit. Step S4: When the comparison result shows that the transient fluctuation rate of the bus voltage exceeds the voltage drop safety threshold, determine the frequency adjustment compensation amount based on the drop depth of the real-time DC bus voltage and the transient fluctuation rate of the bus voltage. Step S5: Retrieve the current drive frequency of the frequency converter, add the frequency adjustment compensation amount to the current drive frequency, generate a transient frequency reduction command and send it to the frequency converter. Step S6: The variable frequency drive lowers the operating frequency of the centrifugal water pump. The active power unloading on the load side is generated by mapping the shaft power of the centrifugal water pump to the cube of the operating frequency. The active power unloading on the load side offsets the power deficit of the electrochemical energy storage unit during the power ramp-up response hysteresis, so as to suppress the transient voltage drop of the DC bus.

[0006] Preferably, determining the frequency regulation compensation amount includes the following steps: Step S41, calculating the available carrying head difference between the maximum water level of the collection tank and the real-time water level of the collection tank; Step S42, mapping the available carrying head difference to a virtual state of charge that reflects the power absorption capacity of the hydraulic system; Step S43, correcting the voltage droop coefficient based on the virtual state of charge and calculating the frequency regulation compensation amount in combination with the transient fluctuation rate of the bus voltage.

[0007] Preferably, step S6 further includes implementing a fluid dynamics limiting step: step S61, setting a limit rate of change for the decrease in the operating frequency of the centrifugal pump; step S62, when the frequency modulation slope corresponding to the transient frequency reduction command exceeds the limit rate of change, cutting off the frequency change rate of the centrifugal pump to the limit rate of change, and allocating the excess voltage smoothing task to the electrochemical energy storage unit.

[0008] Preferably, before determining the frequency adjustment compensation amount, the method further includes: step S44, setting a voltage fluctuation dead zone for the frequency adjustment compensation amount; step S45, locking the frequency adjustment compensation amount to 0 when the absolute value of the fluctuation of the real-time DC bus voltage is less than 2% of the rated voltage.

[0009] Preferably, when the real-time voltage of the DC bus does not trigger the voltage drop safety threshold, the method further includes: step S71, collecting the real-time water level of the water collection tank and the real-time state of charge of the electrochemical energy storage unit; step S72, correcting the rated operating frequency of the frequency converter driver according to the predicted deviation of the real-time output power of the photovoltaic array.

[0010] Preferably, the frequency converter uses a voltage follower control mode, which has a higher priority than the conventional speed regulation logic built into the frequency converter, so that the response characteristics of the centrifugal water pump are coupled in real time with the transient change process of the DC bus voltage.

[0011] Preferably, after step S6, the method further includes: step S81, real-time monitoring of the output power ramp-up status signal of the electrochemical energy storage unit; step S82, when the output power ramp-up status signal indicates that the power balance has been restored, gradually restoring the operating frequency of the centrifugal water pump from the transient frequency reduction command to the current driving frequency.

[0012] Preferably, the method further includes: step S91, statistically analyzing the trigger frequency of transient frequency reduction commands and the timing characteristics of DC bus real-time voltage drops; step S92, calculating the health evaluation index of the independent microgrid system based on the statistical results, and using the health evaluation index as the basis for determining the stability of DC bus real-time voltage.

[0013] Preferably, in step S1, the real-time DC bus voltage is obtained using a high-frequency voltage sampling circuit with a sampling frequency of not less than 10kHz, which is used to provide the bus voltage transient fluctuation rate required for transient stability analysis.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. In the coordinated power supply and control of water collection and irrigation, by establishing a dynamic mapping relationship between the transient fluctuation rate of DC bus voltage and the frequency of variable frequency drive, the centrifugal pump is transformed from a passive power consumption unit into a flexible damping node with bus voltage support capability. Utilizing the physical characteristic that the shaft power of the centrifugal pump decreases proportionally to the cube of the operating frequency, when the photovoltaic output suddenly drops due to meteorological disturbances, the nonlinear rapid unloading of active power on the load side compensates for the active power deficit of the microgrid in situ within the physical lag window of the energy storage system's power ramp-up response. This mechanism physically blocks the causal chain of transient power imbalance evolving into voltage collapse, eliminates the strong dependence of the islanded system on the rapid discharge capability of the large-capacity electrochemical energy storage system, and enhances the transient stability of the microgrid under extreme operating conditions.

[0015] 2. This invention achieves a substantial and deep integration of hydraulic potential energy boundaries and power dispatch logic by constructing a virtual state of charge coupled with the physical constraints of the water collection system. It dynamically corrects the voltage droop coefficient using the water level deviation of the collection pool, enabling voltage regulation commands to adaptively adapt to the fluid dynamic safety threshold of the water collection network. This cross-domain collaborative mechanism translates the mechanical inertia of the water collection system into a virtual power buffer layer of the microgrid, ensuring that the hydraulic system does not overflow or idle at low frequencies. This approach effectively reduces the static energy storage redundancy capacity that the system is forced to configure to cope with random disturbances while ensuring irrigation process requirements, thereby improving the overall operational economy of the distributed energy supply system.

[0016] 3. This invention introduces a fluid dynamics boundary limiting element and a voltage dead zone compensation mechanism into the frequency regulation link to ensure the physical compatibility between high-frequency electrical regulation actions and low-frequency mechanical fluid characteristics. While pursuing millisecond-level power balance, it limits the slope of frequency change to avoid physical damage caused by water hammer effect in the pipeline network, and uses the dead zone element to filter random fluctuation noise of photovoltaic output. This logic closed loop under multiple physical constraints effectively prevents unnecessary thermal fatigue damage to the inverter power module. While ensuring the electrical performance indicators of the power grid, it improves the long-term operational reliability and intrinsic safety level of the entire equipment in complex environments in remote areas. Attached Figure Description

[0017] Figure 1 This is a flowchart of the source-load coordinated scheduling and control process for the photovoltaic microgrid and water collection irrigation system of the present invention. Figure 2 This is a logic architecture diagram for generating frequency reduction instructions that couples hydraulic potential energy with bus voltage characteristics according to the present invention.

[0018] The objectives, features, and advantages of this invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0020] A method for coordinated energy supply dispatch and control of photovoltaic microgrids and water collection irrigation includes the following steps: Step S1: Collect the real-time DC bus voltage, real-time output power of the photovoltaic array, and real-time water level of the water collection tank of the independent microgrid system. Step S2: Calculate the first derivative of the real-time DC bus voltage with respect to time to obtain the transient fluctuation rate of the bus voltage; Step S3: Compare the transient fluctuation rate of the bus voltage with the preset voltage drop safety threshold. The voltage drop safety threshold is determined based on the power ramp-up response hysteresis time of the electrochemical energy storage unit. Step S4: When the comparison result shows that the transient fluctuation rate of the bus voltage exceeds the voltage drop safety threshold, determine the frequency adjustment compensation amount based on the drop depth of the real-time DC bus voltage and the transient fluctuation rate of the bus voltage. Step S5: Retrieve the current drive frequency of the frequency converter, add the frequency adjustment compensation amount to the current drive frequency, generate a transient frequency reduction command and send it to the frequency converter. Step S6: The variable frequency drive lowers the operating frequency of the centrifugal water pump. The active power unloading on the load side is generated by mapping the shaft power of the centrifugal water pump to the cube of the operating frequency. The active power unloading on the load side offsets the power deficit of the electrochemical energy storage unit during the power ramp-up response hysteresis, so as to suppress the transient voltage drop of the DC bus.

[0021] Preferably, determining the frequency regulation compensation amount includes the following steps: Step S41, calculating the available carrying head difference between the maximum water level of the collection tank and the real-time water level of the collection tank; Step S42, mapping the available carrying head difference to a virtual state of charge that reflects the power absorption capacity of the hydraulic system; Step S43, correcting the voltage droop coefficient based on the virtual state of charge and calculating the frequency regulation compensation amount in combination with the transient fluctuation rate of the bus voltage.

[0022] Preferably, step S6 further includes implementing a fluid dynamics limiting step: step S61, setting a limit rate of change for the decrease in the operating frequency of the centrifugal pump; step S62, when the frequency modulation slope corresponding to the transient frequency reduction command exceeds the limit rate of change, cutting off the frequency change rate of the centrifugal pump to the limit rate of change, and allocating the excess voltage smoothing task to the electrochemical energy storage unit.

[0023] Preferably, before determining the frequency adjustment compensation amount, the method further includes: step S44, setting a voltage fluctuation dead zone for the frequency adjustment compensation amount; step S45, locking the frequency adjustment compensation amount to 0 when the absolute value of the fluctuation of the real-time DC bus voltage is less than 2% of the rated voltage.

[0024] Preferably, when the real-time voltage of the DC bus does not trigger the voltage drop safety threshold, the method further includes: step S71, collecting the real-time water level of the water collection tank and the real-time state of charge of the electrochemical energy storage unit; step S72, correcting the rated operating frequency of the frequency converter driver according to the predicted deviation of the real-time output power of the photovoltaic array.

[0025] Preferably, the frequency converter uses a voltage follower control mode, which has a higher priority than the conventional speed regulation logic built into the frequency converter, so that the response characteristics of the centrifugal water pump are coupled in real time with the transient change process of the DC bus voltage.

[0026] Preferably, after step S6, the method further includes: step S81, real-time monitoring of the output power ramp-up status signal of the electrochemical energy storage unit; step S82, when the output power ramp-up status signal indicates that the power balance has been restored, gradually restoring the operating frequency of the centrifugal water pump from the transient frequency reduction command to the current driving frequency.

[0027] Preferably, the method further includes: step S91, statistically analyzing the trigger frequency of transient frequency reduction commands and the timing characteristics of DC bus real-time voltage drops; step S92, calculating the health evaluation index of the independent microgrid system based on the statistical results, and using the health evaluation index as the basis for determining the stability of DC bus real-time voltage.

[0028] Preferably, in step S1, the real-time DC bus voltage is obtained using a high-frequency voltage sampling circuit with a sampling frequency of not less than 10kHz, which is used to provide the bus voltage transient fluctuation rate required for transient stability analysis.

[0029] Example 1: In an independent microgrid system equipped with an electrochemical energy storage unit and disconnected from the main power grid, the system drives a 15kW variable frequency centrifugal water pump at full load. The solar radiation intensity is reduced to 850W / m² due to cloud cover. 2 Reduced to 320W / m 2 As a result, the real-time output power of the photovoltaic array decreases. The electrochemical energy storage unit, limited by the electrochemical reaction rate, experiences a power ramp-up response lag of approximately 120ms. The centrifugal pump maintains its original speed and draws rated active power due to the mechanical inertia of the rotor and the water column in the pipeline. This transient imbalance of source and load active power causes the real-time DC bus voltage to drop towards the grid disconnection protection safety limit. The controller collects the real-time DC bus voltage and the real-time water level in the collection tank, calculates the first derivative of the real-time DC bus voltage with respect to time to obtain the transient fluctuation rate of the bus voltage, and determines the response time based on the power ramp-up response of the electrochemical energy storage unit. When the voltage drop safety threshold is determined by the hysteresis time, the current drive frequency of the frequency converter is extracted. The frequency adjustment compensation amount is determined according to the real-time voltage drop depth of the DC bus and the transient fluctuation rate of the bus voltage. The frequency adjustment compensation amount is superimposed on the current drive frequency to generate a transient frequency reduction command and send it to the frequency converter. The frequency converter reduces the operating frequency of the centrifugal pump according to the command. The active power unloading amount on the load side is generated through the cubic proportional mapping relationship between the centrifugal pump shaft power and the operating frequency. Since the centrifugal pump rotor has mechanical inertia, its physical speed cannot change abruptly within a hundred millisecond scale.

[0030] In this process, the present invention does not rely on the instantaneous physical decrease in mechanical speed, but is based on the electromagnetic transient response mechanism of the inverter side of the variable frequency drive. Specifically, when the transient frequency reduction command is issued to the pulse width modulation (PWM) control unit of the frequency converter, the stator voltage frequency output by the inverter undergoes a millisecond-level step reduction. Due to the mechanical inertia of the motor rotor, it still maintains the original synchronous frequency and speed. The electromagnetic slip angle of the motor changes rapidly and may even become instantaneously negative. According to the transient electromagnetic torque law of AC motors, the active reduction of the stator voltage frequency causes the motor to... The stator magnetic field rotation speed decreases, thereby achieving a rapid reduction in kinetic energy feedback or active power extraction to the DC bus under the mechanical inertia of the rotor. This electromagnetic active power unloading occurs on the order of milliseconds, and its amplitude is proportional to the cube of the frequency change. Thus, before the physical rotational speed has changed significantly, that is, within the power ramp-up response hysteresis window of the electrochemical energy storage unit, the active power deficit is filled. Based on the transient electromagnetic torque law of AC motors, and utilizing the hardware topology of the frequency converter driver directly connected to the microgrid bus on the DC side, the frequency reduction command is issued to instantly increase... The relative slip angle between the stator voltage and the rotor flux linkage causes a transient attenuation of the electromagnetic active power drawn by the motor from the DC bus. This transient active power unloading is directly included in the Kirchhoff current node balancing network of the microgrid's DC bus, filling the millisecond-level power deficit caused by the tracking time of the internal control link and phase-locked loop of the energy storage converter. After the system passes through the transient electromagnetic abrupt change period and enters the actual decrease stage of mechanical speed, the available carrying head difference is calculated based on the maximum water level and the real-time water level of the sump. This available carrying head difference is then mapped to reflect the absorbable power of the hydraulic system. The virtual state of charge of the capacity is used to correct the voltage droop coefficient. The active power unloading on the load side offsets the power deficit of the electrochemical energy storage unit during the power ramp-up response hysteresis, suppresses the transient voltage drop of the DC bus, and restores the real-time voltage of the DC bus to steady state. This control logic converts the nonlinear mechanical load of the fluid into an active power damper. By converting the mechanical rotational kinetic energy of the hydraulic system into a transient active power buffer for the DC bus of the microgrid, the electrochemical energy storage configuration capacity required for the independent microgrid system to maintain transient stability is reduced.

[0031] Example 2: This example constructs a photovoltaic microgrid test platform with a rated power of 50kW, configured with a 20kWh lithium iron phosphate electrochemical energy storage unit and a 15kW variable frequency drive centrifugal water pump. The test data originates from real-time physical sensor signals acquired by the hardware-in-the-loop simulation system. Gaussian white noise with a signal-to-noise ratio of 20dB is actively superimposed on the DC bus voltage sensing channel to simulate an industrial electromagnetic environment. The system sampling period is determined by balancing the real-time performance of transient voltage capture and the controller's computational load. When the monitored signal contains high-frequency transient characteristics with a 120ms power ramp-up response hysteresis time and sampling aliasing needs to be avoided, the lower limit value that meets the capture requirements is calculated based on the sampling theorem, and the sampling period is set to 2ms. A problem intensity gradient control system is constructed under the condition of sudden change in light intensity, with the initial light intensity of the photovoltaic array set to 1000W / m². 2 The light intensity was set to drop sharply to 600W / m 2 300W / m 2 100W / m 2 Three levels of disturbance were established, including a control group 1 where transient frequency reduction commands were removed and droop regulation relied solely on electrochemical energy storage units; a control group 2 where the voltage drop safety threshold was set to exceed the physical limit of the power ramp-up response hysteresis time of the electrochemical energy storage units; and an experimental group applying a photovoltaic microgrid and water collection irrigation coordinated power supply scheduling and control method. The controller collected the real-time DC bus voltage containing Gaussian white noise, filtered the noise through differential calculation, and obtained the transient fluctuation rate of the bus voltage. The test was conducted when the light intensity suddenly dropped to 300W / m. 2 Under the disturbance level, the real-time DC bus voltage of control group 1 dropped to the 510V protection threshold within 85ms. When the transient fluctuation rate of the bus voltage in the test group exceeded the voltage drop safety threshold, the current driving frequency of the frequency converter driver was retrieved at 50Hz. Based on the drop depth of the real-time DC bus voltage, the frequency adjustment compensation was determined to be -5.2Hz, and the frequency adjustment compensation was superimposed on the current driving frequency to generate a transient frequency reduction command of 44.8Hz.

[0032] The variable frequency drive receives a transient frequency reduction command and lowers the operating frequency of the centrifugal water pump. It generates a 4.2kW ​​load-side active power unloading through a cubic proportional relationship between the centrifugal pump shaft power and the operating frequency. This fills the power deficit on the source side during the power ramp-up response lag of the electrochemical energy storage unit, causing the DC bus real-time voltage to converge to the steady-state range after dropping to a minimum of 565V. Gradient tests across stepped disturbance levels show that as the magnitude of the light intensity drop increases, the frequency adjustment compensation output of the test group exhibits a non-linear growth. When the light intensity drops to 100W / m², the compensation increases. 2When the operating frequency of the centrifugal pump drops to 35Hz and enters the performance inflection point of fluid cavitation, the frequency adjustment compensation amount corresponding to 35Hz establishes the physical constraint lower limit of the transient frequency reduction command. The control group 2 caused the water hammer effect in the pipeline network due to the voltage drop safety threshold setting exceeding the constraint lower limit. The test group combined the active power unloading amount on the load side and the voltage droop coefficient corrected by the virtual state of charge to confirm the extension effect of the fluid nonlinear unloading mechanism on the transient voltage stability domain of the independent microgrid.

[0033] Example 3: In an independent microgrid system configured with photovoltaic arrays and electrochemical energy storage units, the determination of frequency regulation compensation and voltage droop coefficient is controlled by a multi-dimensional physical parameter mapping mechanism at the underlying level to eliminate the offset of control parameter settings when the active power of the source and load is transiently unbalanced. The controller collects the real-time water level of the water collection tank. and the maximum water level of the preset water collection tank within the system. with the bottom area of ​​the collection tank The difference between the maximum water level and the real-time water level in the collection tank is used to obtain the available carrying capacity head difference. The usable water mass is output by multiplying the available head difference by the product of the bottom area of ​​the collection tank and the water density. The usable water mass is then multiplied by the acceleration due to gravity and the pump head. The theoretical absorbable fluid potential energy was calculated. The controller divides the theoretically absorbable fluid potential energy by the nominal energy capacity of the electrochemical energy storage unit. Extract the scalar ratio of the two and output a dimensionless virtual state of charge. The water density is taken as . The acceleration due to gravity is taken as: Retrieve the system's preset reference voltage droop factor Multiply the reference voltage droop factor by the virtual state of charge output corrected voltage droop factor. ,Right now Establish quantitative constraints of the fluid potential energy boundary on the electrical transient control loop of the microgrid, and correct the voltage droop coefficient. This reflects the weight of the hydraulic system as a virtual energy storage unit in grid regulation, when the water level in the collection tank is low and the available head difference is large. When it is large, the calculated value is An increase in the droop coefficient indicates that the hydraulic system has greater power throughput redundancy. This improves the inverter's gain sensitivity to bus voltage fluctuations, allowing the system to perform deeper frequency reduction when facing voltage dips. This correction mechanism essentially transforms long-scale potential redundancy into a short-scale transient adjustment proportional gain limiter. In actual implementation, The update cycle is set to the minute level and is sent from the background energy management system to the underlying controller as a gain operator of the transient damping control link, thereby logically realizing the dynamic constraint of the micro electrical control envelope by the macro hydraulic conditions.

[0034] In the transient voltage damping control link, the controller calculates the rated voltage of the DC bus. Real-time voltage of DC bus The difference generates voltage drop depth The obtained bus voltage transient fluctuation rate Multiply by the power ramp-up response hysteresis of the electrochemical energy storage unit Expected output feedforward voltage sag The controller adds the voltage sag depth to the expected feedforward voltage sag amount to generate a comprehensive voltage deviation benchmark. Retrieve the preset frequency and voltage sensitivity coefficient inside the frequency converter driver The specific frequency adjustment compensation amount is calculated by multiplying the comprehensive voltage deviation reference by the frequency voltage sensitivity coefficient. The specific formula is as follows: ,in, This is the frequency adjustment compensation amount. This is the rated voltage of the DC bus. This is the real-time voltage of the DC bus. The transient fluctuation rate of the bus voltage. This refers to the power ramp-up response hysteresis time. The frequency voltage sensitivity coefficient is used to generate a transient frequency reduction command by superimposing the frequency adjustment compensation amount onto the current drive frequency.

[0035] Photovoltaic array output power In the scenario of a standalone microgrid operating under real-time fluctuations, the controller inputs the real-time output power of the photovoltaic array to the transient voltage damping control link, and calculates the ratio of the real-time output power of the photovoltaic array to the nominal active power of the photovoltaic array to determine the dynamic gain operator. The controller retrieves the frequency adjustment compensation amount. The initial weighting value is calculated based on the scaling principle, following the formula. Operations, where, This is the initial correction compensation amount. The dimensionless dynamic gain operator takes values ​​greater than 0 and less than or equal to 1. The controller reads the lower limit frequency constant stored in the register as the original frequency adjustment compensation amount. This corresponds to the critical head static pressure at which the fluid in the pipeline network cannot flow back. It then determines in real time whether the sum of the current drive frequency and the initial correction compensation amount is lower than the lower limit frequency constant. This lower limit frequency constant is calculated using the pump's QH characteristic curve and the actual head requirement of the irrigation network. Specifically, during system installation and commissioning, the height difference between the current collection tank and the irrigation area is read by sensors, converted into static pressure, and the minimum operating speed frequency corresponding to that pressure is found in the pump sample data. For example, for a system with a head of 30 meters, the corresponding pump balance frequency might be 30Hz. This value is written into the register as the lower limit frequency constant to prevent excessive frequency reduction that could lead to backflow and cavitation damage in the pipeline network. If the value is lower, the difference between the lower limit frequency constant and the current drive frequency is extracted and used to replace the initial correction compensation amount. The product operation and threshold dynamic truncation steps objectively constitute the dynamic gain operator. Frequency adjustment compensation amount The amplitude-limiting weighting process is performed, and the corrected frequency regulation compensation is superimposed on the current driving frequency of the frequency converter to generate a transient frequency reduction command. This cooperative mechanism uses the current power state of the photovoltaic array as a feedback constraint on the frequency regulation intensity, which suppresses the DC bus voltage oscillation caused by the mismatch between the load-side active power unloading regulation intensity and the source-side power fluctuation amplitude.

[0036] Example 4: When an independent microgrid system faces a situation where the physical response characteristics of the electrochemical energy storage unit deviate due to aging, the controller sends a rated discharge command to the electrochemical energy storage unit, collects the real-time discharge current at the output of the electrochemical energy storage unit, calculates the time taken for the real-time discharge current to rise from zero to 90% of the rated discharge current, and records this time as the power ramp-up response hysteresis time. Read the real-time cell operating temperature collected by the ambient temperature sensor, and establish a system that includes the real-time cell operating temperature and power ramp-up response hysteresis time. The corresponding relationship table is used to retrieve the matching power ramp-up response hysteresis time when subsequent sudden changes in light intensity cause bus voltage fluctuations. Input to the transient voltage damping control link.

[0037] When the system is in steady-state output mode of the photovoltaic array, the controller gradually adjusts the operating frequency of the centrifugal water pump, records the steady-state DC bus voltage values ​​corresponding to the operating points when the centrifugal water pump operates at 50%, 75%, and 100% of the rated frequency, and determines the ratio of frequency deviation to voltage deviation between adjacent operating points to output multiple sets of discrete sensitivity values. The controller uses the least squares algorithm to linearly fit the multiple sets of discrete sensitivity values, extracts the global slope parameter that maps the correlation between the water pump load characteristics and the electrical stiffness of the microgrid, and writes the global slope parameter into the storage unit of the frequency converter driver as the frequency and voltage sensitivity coefficient. This calibration process converts the mechanical friction characteristics and hydrostatic pressure characteristics of the hydraulic network into the constraint boundary for the transient active power dispatch of the microgrid.

[0038] Example 5: In an independent microgrid deployment site with high-frequency sampling random interference in the DC bus voltage sensing channel, the transient fluctuation rate of the bus voltage is... The calculation accuracy is constrained by the amplitude of digital sampling noise. The controller establishes a sliding window with 5 sampling points and a time span of 10ms to extract the real-time DC bus voltage. The real-time DC bus voltage corresponding to the first sampling point within the sliding window. Real-time DC bus voltage corresponding to the end sampling point The difference between the two values ​​is calculated and divided by a 10ms window duration to determine the bus voltage transient fluctuation rate. The specific calculation formula is expressed as follows: ,in, The transient fluctuation rate of the bus voltage. This represents the real-time DC bus voltage corresponding to the sampling point at the end of the sliding window. For the real-time DC bus voltage corresponding to the sampling point at the beginning of the sliding window, the controller applies a sliding window mean slope processing step to filter out the interference of discrete noise points on the transient decision logic, thereby increasing the frequency adjustment compensation amount. The output results are synchronized with the evolution trend of the DC bus voltage, avoiding the situation where high-frequency jitter accidentally triggers the centrifugal water pump to reduce frequency and unload.

[0039] The system starts with a voltage dip safety threshold before commissioning. The calibration steps involve debugging the terminal to trigger the step power regulation action of the electrochemical energy storage unit and monitoring the real-time voltage of the DC bus. The maximum voltage recovery slope observed after the steady-state value falls to its lowest point and then rises back to 95% of the rated voltage is shown in the figure. The controller extracts this value and sets the voltage drop below the safety threshold. Set as maximum voltage recovery slope The transient voltage damping control link is limited to 1.2 times the rated voltage, and it only intervenes when the active power deficit exceeds the physical regulation limit of the electrochemical energy storage unit. The controller will reduce the calibrated voltage drop to a safe threshold. Compared with the bus voltage transient fluctuation rate obtained by real-time calculation Continuous comparison, when the bus voltage transient fluctuation rate The absolute value exceeds the voltage drop safety threshold. A transient frequency reduction command is generated and sent to the frequency converter driver. The mechanical inertia of the centrifugal pump is used to generate the load-side active power unloading. This calibration step establishes the graded response mapping of the microgrid electrical control loop to the intensity of external disturbances, and maintains the DC bus transient voltage balance of the independent microgrid system under sudden change in light conditions.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for coordinated energy supply dispatch and control of photovoltaic microgrids and water collection irrigation, characterized in that, Includes the following steps: Step S1: Collect the real-time DC bus voltage, real-time output power of the photovoltaic array, and real-time water level of the water collection tank of the independent microgrid system. Step S2: Calculate the first derivative of the real-time DC bus voltage with respect to time to obtain the transient fluctuation rate of the bus voltage; Step S3: Compare the transient fluctuation rate of the bus voltage with the preset voltage drop safety threshold. The voltage drop safety threshold is determined based on the power ramp-up response hysteresis time of the electrochemical energy storage unit. Step S4: When the comparison result shows that the transient fluctuation rate of the bus voltage exceeds the voltage drop safety threshold, determine the frequency adjustment compensation amount based on the drop depth of the real-time DC bus voltage and the transient fluctuation rate of the bus voltage. Step S5: Retrieve the current drive frequency of the frequency converter, add the frequency adjustment compensation amount to the current drive frequency, generate a transient frequency reduction command and send it to the frequency converter. Step S6: The variable frequency drive lowers the operating frequency of the centrifugal water pump. The active power unloading on the load side is generated by mapping the shaft power of the centrifugal water pump to the cube of the operating frequency. The active power unloading on the load side offsets the power deficit of the electrochemical energy storage unit during the power ramp-up response hysteresis, so as to suppress the transient voltage drop of the DC bus.

2. The method for coordinated energy supply scheduling and control of photovoltaic microgrids and water collection irrigation according to claim 1, characterized in that, Determining the frequency regulation compensation amount includes the following steps: Step S41, calculate the available carrying head difference between the maximum water level of the collection tank and the real-time water level of the collection tank; Step S42, map the available carrying head difference into a virtual state of charge that reflects the power absorption capacity of the hydraulic system; Step S43, correct the voltage droop coefficient according to the virtual state of charge and calculate the frequency regulation compensation amount in combination with the transient fluctuation rate of the bus voltage.

3. The method for coordinated energy supply scheduling and control of photovoltaic microgrids and water collection irrigation according to claim 1, characterized in that, Step S6 also includes implementing a fluid dynamics limiting step: Step S61, setting the limit rate of change for the decrease in the operating frequency of the centrifugal pump; Step S62, when the frequency adjustment slope corresponding to the transient frequency reduction command exceeds the limit rate of change, cutting off the frequency change rate of the centrifugal pump to the limit rate of change, and allocating the excess voltage smoothing task to the electrochemical energy storage unit.

4. The method for coordinated energy supply scheduling and control of photovoltaic microgrids and water collection irrigation according to claim 1, characterized in that, Before determining the frequency regulation compensation amount, the process includes: step S44, setting a voltage fluctuation dead zone for the frequency regulation compensation amount; and step S45, locking the frequency regulation compensation amount to 0 when the absolute value of the fluctuation of the real-time DC bus voltage is less than 2% of the rated voltage.

5. The method for coordinated energy supply scheduling and control of photovoltaic microgrids and water collection irrigation according to claim 1, characterized in that, When the real-time voltage of the DC bus does not trigger the voltage drop safety threshold, the method further includes: step S71, collecting the real-time water level of the water collection tank and the real-time state of charge of the electrochemical energy storage unit; step S72, correcting the rated operating frequency of the frequency converter driver according to the predicted deviation of the real-time output power of the photovoltaic array.

6. The method for coordinated energy supply scheduling and control of photovoltaic microgrids and water collection irrigation according to claim 1, characterized in that, The variable frequency drive adopts a voltage follower control mode, which has a higher priority than the conventional speed regulation logic built into the variable frequency drive, so that the response characteristics of the centrifugal water pump are coupled in real time with the transient change process of the DC bus voltage.

7. The method for coordinated energy supply scheduling and control of photovoltaic microgrids and water collection irrigation according to claim 1, characterized in that, Step S6 is followed by: Step S81, real-time monitoring of the output power ramp-up status signal of the electrochemical energy storage unit; Step S82, when the output power ramp-up status signal indicates that the power balance has been restored, gradually restoring the operating frequency of the centrifugal water pump from the transient frequency reduction command to the current driving frequency.

8. The method for coordinated energy supply scheduling and control of photovoltaic microgrid and water collection irrigation according to claim 1, characterized in that, The method also includes: step S91, statistically analyzing the trigger frequency of transient frequency reduction commands and the timing characteristics of DC bus real-time voltage drops; step S92, calculating the health evaluation index of the independent microgrid system based on the statistical results, and using the health evaluation index as the basis for determining the stability of DC bus real-time voltage.

9. The method for coordinated energy supply scheduling and control of photovoltaic microgrid and water collection irrigation according to claim 1, characterized in that, In step S1, the real-time DC bus voltage is obtained using a high-frequency voltage sampling circuit with a sampling frequency of not less than 10kHz, which is used to provide the bus voltage transient fluctuation rate required for transient stability analysis.

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