Photovoltaic load shedding operation-based water-light micro-grid regulation and control method under off-grid condition

Abstract

The invention discloses a water-light micro-grid regulation and control method based on photovoltaic load shedding operation under an off-grid condition, and the method comprises the following steps: 1, carrying out the maximum power tracking test of a photovoltaic power generation system in a micro-grid under different illumination conditions before the off-grid operation of a micro-grid system, recording the maximum power point voltage and power value of different illumination, and calculating the maximum power point voltage and power value of the photovoltaic power generation system; establishing a power-voltage curve of the system; 2, measuring the illumination intensity of the current working environment of the photovoltaic power generation system, and setting voltage deloading operation of the photovoltaic power generation system according to the current illumination intensity; the micro-grid controller sets constant power generation of the small hydropower station according to the currently measured local load capacity and the output power of the photovoltaic power generation system; 3, judging the frequency and the frequency change rate of the current micro-grid system, and adjusting the generating capacity of the photovoltaic power generation system and the small hydropower station; and 4, measuring the voltage Upv and the power Ppv output by the photovoltaic power generation system, judging (dPpv / dUpv), and updating the voltage value and the power value of the maximum power point in the step 1 according to real-time data.

Description

Technical Field

[0001] The present invention belongs to the field of water-photovoltaic microgrid regulation and control, and in particular relates to a water-photovoltaic microgrid regulation and control method based on photovoltaic load reduction operation under off-grid conditions. Background Art

[0002] my country's southeastern and southwestern mountainous areas are rich in hydropower resources, and small hydropower has broad prospects for development. Under the dual carbon goals, distributed photovoltaics have developed rapidly, and more and more distributed power sources such as photovoltaics and hydropower have been connected to the power grid through long-distance transmission lines. At the same time, due to the remote geographical location and complex terrain, the power grid in mountainous areas often has relatively poor power supply reliability due to long power supply lines and large power supply radius. When the upper power grid fails and loses power, relying on the sufficient local photovoltaic and hydropower resources to form a microgrid system is an effective guarantee for the reliability of power supply for mountain residents.

[0003] When operating off-grid, due to the poor frequency regulation capability of small hydropower stations, it is difficult to ensure that the frequency of the microgrid system fluctuates within the normal range by relying solely on small hydropower. In response to the frequency stability issue, existing scholars mainly increase energy storage to ensure the stability of the microgrid system frequency.

[0004] During grid-connected operation, with the large-capacity grid connection of photovoltaic power, some scholars have proposed to reduce the load of photovoltaic power and reserve some active power for frequency modulation to achieve active support for system frequency changes.

[0005] In the existing technology, when operating off-grid, due to the poor frequency regulation capability of small hydropower stations, it is difficult to ensure that the frequency of the microgrid system fluctuates within the normal range by relying solely on small hydropower for regulation. In order to solve the problem of frequency stability, existing scholars mainly increase energy storage to ensure the stability of the frequency of the microgrid system. However, in engineering applications, the capacity of energy storage power stations is usually set to be large. When connected to the grid, the energy storage is often idle, which increases investment and also causes a certain amount of resource waste.

[0006] Under grid-connected operation, with the large capacity of photovoltaic grid-connected, some scholars proposed to operate photovoltaic load-reducing, reserve some active power to participate in the system frequency regulation, and realize active support for system frequency changes. Han Pingping and other scholars proposed to obtain the current maximum power operation point by setting the master-slave photovoltaic array, and then realize load reduction control (active frequency response method of photovoltaic power station based on load reduction control), but their research mainly focuses on the grid-connected situation, and does not consider the coordination and cooperation between the off-grid and other distributed power sources. Li Huayi and other scholars designed a photovoltaic load reduction tracking method based on offline fitting (Study on Virtual Synchronous Generator Control of Photovoltaic Load Reduction in Independent Microgrids). The slope mutation data points of the photovoltaic load reduction curve under different irradiances are selected as segmentation points, and the measured data are used for linear fitting to obtain the fitting parameters and establish a four-segment linear function of photovoltaic load reduction power. This method can better approach the photovoltaic power voltage curve, but the four-segment linear function has a large amount of data, and the data needs to be collected for re-fitting under different light intensities. It takes a long time and is not suitable for off-grid operation occasions that rely solely on photovoltaics for frequency regulation. Summary of the invention

[0007] In view of the above problems, the present invention proposes a hydro-photovoltaic microgrid control method based on photovoltaic load reduction operation under off-grid conditions. The photovoltaic power-voltage curve is established by the method of offline fitting + online parameter update, and a fast frequency response is achieved according to the power-voltage curve. The photovoltaic spare capacity is used to replace the regulating function of energy storage, so as to ensure the frequency stability of the microgrid system while reducing the investment in the microgrid system.

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

[0009] A method for regulating a hydro-photovoltaic microgrid based on photovoltaic load reduction operation under off-grid operation comprises the following steps:

[0010] Step 1: Before the microgrid system is off-grid, a maximum power tracking test is performed on the photovoltaic power generation system in the microgrid under different light intensities, the maximum power point voltage-power value under different light intensities is recorded, and a linear function is established to describe the power-voltage curve of the photovoltaic power generation system;

[0011] Step 2: Measure the light intensity under the current working environment of the photovoltaic power generation system. According to the data in step 1, the photovoltaic controller sets the photovoltaic power generation unit to operate at reduced load; the microgrid controller sets the small hydropower station to generate constant power according to the currently measured local load and the output power of the photovoltaic power generation system;

[0012] Step 3: Measure the frequency of the microgrid system, determine the current frequency of the microgrid system and the frequency change rate, and adjust the power generation of the photovoltaic power generation system and the small hydropower station;

[0013] Step 4: Measure the output voltage U of the photovoltaic power generation system pv With power Ppv , for (dP pv / dU pv ) to make a judgment to adjust the power generation of the photovoltaic power generation system and the small hydropower station, and update the maximum power point voltage and power value in step 1 according to the real-time data.

[0014] Furthermore, in step 1, the test is based on the factory technical parameters of the photovoltaic components and simulates various light intensities. During the test, the maximum power point voltage and power values ​​under different light intensities are recorded and stored in detail to form a data table. The table is stored in the photovoltaic controller so that the control program can read and write.

[0015] Furthermore, in step 1, when the voltage is in the range [0-U mi ], the power-voltage curve is fitted as a straight line passing through the origin, with a slope of I i , the power-voltage curve is expressed as:

[0016] P pvi =I i ·U pvi

[0017]

[0018] Where P pvi is the photovoltaic output power fitting value under light intensity i; U pvi is the photovoltaic output voltage fitting value under light intensity i; U mi is the actual value of the photovoltaic output maximum power point voltage under light intensity i; P mi is the actual maximum power output of the photovoltaic under light intensity i; K rel is the slope correction coefficient;

[0019] When the voltage exceeds U mi After that, the power-voltage curve shows a downward trend, and the decline is large. A small voltage change will lead to a large power fluctuation, which will control the output voltage of the photovoltaic power generation system to be less than the maximum power point voltage value U mi .

[0020] Further, in step 2, the microgrid controller sets the photovoltaic power generation system to 0.45U under the current light intensity. mi Voltage load reduction operation, U mi It is the actual value of the photovoltaic output maximum power point voltage under light intensity i.

[0021] Furthermore, the reference value of power generation of small hydropower station P hdref for:

[0022] P hdref =P load -P pvi

[0023] Among them, P load is the currently measured local load, P pvi is the fitted value of the photovoltaic output power under light intensity i.

[0024] Furthermore, in step 3, the current microgrid system frequency f and the frequency change rate df / dt are judged, and the power generation of the photovoltaic power generation system and the small hydropower station power generation system is adjusted, specifically including:

[0025] When 49.8≤f≤50.2, maintain the current operation status of the photovoltaic power generation system and the small hydropower station power generation system;

[0026] When f>50.2, judge df / dt:

[0027] When df / dt≥0, the photovoltaic power generation system is adjusted to operate with the calculated maximum voltage difference ΔU1, that is, the reference voltage U pvref =U pv -ΔU1; U calculated after load reduction pvref <0, adjust the power generation system of small hydropower stations to reduce power generation;

[0028] When df / dt<0, the photovoltaic power generation system operates with a constant voltage difference ΔU2, that is, the reference voltage U pvref =U pv -ΔU2;

[0029] When f<49.8, judge df / dt:

[0030] When df / dt≤0, the photovoltaic power generation system operates with the calculated maximum voltage difference ΔU1, that is, the reference voltage U pvref =U pv -ΔU1;

[0031] When (dP pv / dU pv )=0, the measured P pv is the maximum power of the photovoltaic power generation unit under the current working conditions, and the measured U pv The maximum power point voltage value of the photovoltaic power generation unit is used to update the data in the data table with the maximum power point voltage value and power value of the current light intensity. At the same time, in order to make the photovoltaic power generation unit always run on the left side of the maximum power point, the power generation system of the small hydropower station is adjusted to increase the power generation;

[0032] When df / dt>0, the photovoltaic power generation system operates with a constant voltage difference ΔU2, that is, the reference voltage U pvref =U pv -ΔU2;

[0033] Where P pv is the actual output power value of the photovoltaic power generation system measured under the current working conditions, U pv It is the actual value of the photovoltaic power generation system output voltage measured under the current working conditions.

[0034] Furthermore, the maximum voltage difference ΔU1 is:

[0035]

[0036] Where P hd is the currently measured power generation of the small hydropower station, I i is the slope of the power-voltage curve, P load is the currently measured local load.

[0037] Furthermore, the constant voltage difference ΔU2 is:

[0038]

[0039] In the formula, K j Is a positive integer.

[0040] Furthermore, the adjustment of the power generation of the small hydropower station increases the power generation or decreases the power generation P hdref for:

[0041] P hdref =P load -0.45*P mi

[0042] Where P load is the currently measured local load; P mi is the actual maximum power output of the photovoltaic under light intensity i;

[0043] Synchronously set the reference voltage of the photovoltaic power generation system to: U pvref =0.45*U mi , U mi It is the actual value of the photovoltaic output maximum power point voltage under light intensity i.

[0044] 1Furthermore, when (dP pv / dU pv )=0, update the maximum power point voltage value and power value under the current working condition;

[0045] According to the power voltage curve of the photovoltaic power generation unit, when (dP pv / dU pv )=0, the measured P pv is the maximum power of the photovoltaic power generation unit under the current working conditions, and the measured U pvThe maximum power point voltage value of the photovoltaic power generation unit is used to update the data in the data table with the maximum power point voltage value and power value of the current light intensity.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. The present invention establishes a photovoltaic power-voltage curve through an offline fitting + online parameter update method, and realizes a fast frequency response according to the power-voltage curve; it can reduce the investment in energy storage of a microgrid system in mountainous areas, and utilize the adjustable capacity of photovoltaics to participate in the system frequency stability control.

[0048] 2. Below the maximum power point, photovoltaics have a certain adjustable capacity; at the same time, compared with traditional generator sets, photovoltaics have rapid adjustment capabilities. The present invention makes full use of the two characteristics of photovoltaics to achieve effective adjustment of the microgrid without energy storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 A structural diagram of a microgrid system in an area according to an embodiment of the present invention;

[0050] Figure 2 Microgrid system control flow chart of an embodiment of the present invention;

[0051] Figure 3 Power-voltage waveforms of photovoltaic engineering models at different temperatures;

[0052] Figure 4 Power-voltage waveform of the photovoltaic engineering model under different light intensities;

[0053] Figure 5 Control block diagram of a photovoltaic power generation system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0054] 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 in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain 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 ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0055] like Figure 1 As shown, the microgrid system of the off-grid hydro-photovoltaic microgrid control in the mountain area based on photovoltaic load reduction operation in this embodiment includes a small hydropower station, a photovoltaic power generation system, a local load, a substation microgrid controller, etc.

[0056] A method for regulating a hydro-photovoltaic microgrid in a mountainous area based on photovoltaic load shedding operation, such as Figure 2 As shown, the specific implementation method includes the following steps:

[0057] Step 1: Before the microgrid system works, perform a maximum power tracking test on the photovoltaic power generation system in the microgrid under different light intensities, record the maximum power point voltage-power value under different light intensities, and establish a linear function to describe the power-voltage curve of the photovoltaic power generation system.

[0058] The test is based on the factory technical parameters of the photovoltaic modules and simulates various light intensities. During the test, the maximum power point voltage and power values ​​under each light intensity will be recorded and stored in detail to form a data table, as shown in Table 1. This table is stored in the photovoltaic controller so that the control program can read and write. Since the influence of temperature on the maximum power is small, such as Figure 3 The photovoltaic output power and voltage curve of the engineering model is shown. When the temperature changes, the photovoltaic output power does not change much. The working conditions of the photovoltaic power generation system of the present invention only consider different light intensities and ignore the influence of temperature.

[0059] Table 1 Maximum power point voltage and power value of photovoltaic power generation system under different light intensities

[0060]

[0061] (In the table, U m is the maximum power point voltage value under different light intensities; P m is the maximum power value under different light intensities.

[0062] According to the data recorded in Table 1, it is proposed to use a linear function to describe the photovoltaic power generation system in [0-U mi ]Power-voltage curve within voltage, such as Figure 4 As shown, although the photovoltaic power generation system is described by a linear function in [0-U mi ]The power-voltage curve within the voltage has a certain power error, which in turn affects the deviation of frequency regulation, but the voltage has no error. In addition, a fluctuation range of ±0.2Hz is allowed during normal operation of the power grid, so it can be used for an approximate description.

[0063] When the voltage is [0-U mi ], the power-voltage curve is fitted as a straight line passing through the origin, with a slope of I i , the power-voltage curve is expressed as:

[0064] P pvi =I i ·U pvi

[0065]

[0066] Where P pvi is the photovoltaic output power fitting value under light intensity i; U pviis the photovoltaic output voltage fitting value under light intensity i; U mi is the actual value of the photovoltaic output maximum power point voltage under light intensity i; P mi is the actual maximum power output of the photovoltaic under light intensity i; K rel is the slope correction coefficient, which can be 1.2 to 1.3. As a preferred embodiment, K rel It can be 1.2 to 1.3.

[0067] When the voltage exceeds U mi After that, the power-voltage curve shows a downward trend, and the decline is large. A small voltage change will lead to a large power fluctuation. The present invention will control the output voltage of the photovoltaic power generation system to be less than the maximum power point voltage value U mi .

[0068] According to the test data in the above table and the linear function calculation formula, the mathematical expression of the power-voltage curve under different light intensities can be obtained.

[0069] Step 2: The control strategy of the photovoltaic power generation system is as follows: Figure 5 As shown, the specific implementation is as follows:

[0070] First, measure the light intensity S in the current working environment of the photovoltaic power generation system i , the actual value of the photovoltaic power generation system output power P pv The actual value of the output voltage U pv , the grid connection point voltage U of the photovoltaic power generation system connected to the grid through the DC / AC inverter abc With current I abc Then, based on the grid-connected point voltage and current data, the system frequency data is output through a widely used phase-locked loop algorithm; then the system frequency is judged, and the voltage reference signal of the photovoltaic power generation system is output through the power-frequency response control method proposed in the embodiment of the present invention, and the load and small hydropower power signals required in the power-frequency response are transmitted by the microgrid controller of the substation area; finally, according to the difference between the actual output voltage and the voltage reference signal, a current reference signal is generated after the voltage loop, and a modulation signal is generated after the current loop. The modulation signal outputs a modulation pulse through SPWM to control the DC / AC inverter to achieve grid-connected control.

[0071] According to the data in Table 1, the photovoltaic power generation system is initialized according to the current light intensity S i 0.45U mi Voltage load reduction operation, at this time 0.45U mi It is the initialization voltage reference signal. The microgrid controller is based on the current measured local load P load The output power fitting value P of the photovoltaic power generation system pvi Set the constant power generation of small hydropower station, the reference value of power generation of small hydropower station Phdref = P load -P pvi 。

[0072] Step 3. Measure the microgrid system frequency f, the actual value of the small hydropower generation P hd , the local load P load , and the actual output power of the photovoltaic power generation system P pv and the actual output voltage U pv 。

[0073] Step 4. Judge the current microgrid system frequency f and the frequency change rate df / dt. Given that the normal frequency deviation allowable value of China's power system is ±0.2 Hz, then:

[0074] When 49.8 < f < 50.2, maintain the operating states of the current photovoltaic power generation system and the small hydropower station power generation system;

[0075] When f > 50.2, judge df / dt:

[0076] When df / dt ≥ 0, adjust the photovoltaic power generation system to operate with load shedding at the calculated maximum voltage difference ΔU1, that is, the reference voltage U of the photovoltaic power generation system pvref = U pv - ΔU1; when the calculated U after load shedding pvref < 0, adjust the small hydropower station power generation system to reduce the power generation;

[0077] When df / dt < 0, the photovoltaic power generation system operates with load shedding at a constant voltage difference ΔU2, that is, the reference voltage U of the photovoltaic power generation system pvref = U pv - ΔU2.

[0078] When f < 49.8, judge df / dt:

[0079] When df / dt ≤ 0, the photovoltaic power generation system operates with load increase at the calculated maximum voltage difference ΔU1, that is, the reference voltage U of the photovoltaic power generation system pvref = U pv - ΔU1;

[0080] When (dP pv / dU pv ) = 0, the measured P pv at this time is the maximum power of the photovoltaic power generation unit under the current working condition, and the measured U pv is the maximum power point voltage value of the photovoltaic power generation unit. Update the data in Table 1 with the maximum power point voltage value and power value of the current light intensity. At the same time, to make the photovoltaic power generation unit always operate on the left side of the maximum power point, adjust the small hydropower station power generation system to increase the power generation.

[0081] When df / dt>0, the photovoltaic power generation system operates with a constant voltage difference ΔU2, that is, the reference voltage U pvref =U pv -ΔU2.

[0082] Among them, ΔU1 and ΔU2:

[0083]

[0084]

[0085] Where P hd K is the current measured power generation of the small hydropower station. j is a positive integer. As a preferred embodiment, K j The options are 1, 2, 3, n, etc.

[0086] Among them, adjusting the power generation of small hydropower to increase or decrease power generation:

[0087] P hdref =P load -0.45*P mi

[0088] Considering that photovoltaic power generation needs to have a certain range of power regulation capabilities, the reference voltage of the photovoltaic power generation system is set to:

[0089] U pvref =0.45*U mi

[0090] Return to step 3.

[0091] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for regulating a hydro-photovoltaic microgrid based on photovoltaic load reduction operation under off-grid operation, characterized in that: The following steps are involved: Step 1: Before the microgrid system is off-grid, a maximum power tracking test is performed on the photovoltaic power generation system in the microgrid under different light intensities, the maximum power point voltage-power value under different light intensities is recorded, and a linear function is established to describe the power-voltage curve of the photovoltaic power generation system; Step 2: Measure the light intensity under the current working environment of the photovoltaic power generation system. According to the data in step 1, the photovoltaic controller sets the photovoltaic power generation unit to operate at reduced load; the microgrid controller sets the small hydropower station to generate constant power according to the currently measured local load and the output power of the photovoltaic power generation system; Step 3: Measure the frequency of the microgrid system, determine the current frequency of the microgrid system and the frequency change rate, and adjust the power generation of the photovoltaic power generation system and the small hydropower station; Step 4: Measure the output voltage U of the photovoltaic power generation system pv With power P pv , for (dP pv / dU pv ) to make a judgment to adjust the power generation of the photovoltaic power generation system and the small hydropower station, and update the maximum power point voltage and power value in step 1 according to the real-time data.

2. The off-grid hydro-photovoltaic microgrid control method based on photovoltaic load reduction operation according to claim 1 is characterized in that: In step 1, the test is based on the factory technical parameters of the photovoltaic modules and simulates various light intensities. During the test, the maximum power point voltage and power values ​​under different light intensities are recorded and stored in detail to form a data table. The table is stored in the photovoltaic controller so that the control program can read and write.

3. The off-grid hydro-photovoltaic microgrid control method based on photovoltaic load reduction operation according to claim 1 is characterized in that: In step 1, when the voltage is between [0-U mi ], the power-voltage curve is fitted as a straight line passing through the origin, with a slope of I i , the power-voltage curve is expressed as: P pvi =I i ·IN pvi Where P pvi is the photovoltaic output power fitting value under light intensity i; U pvi is the photovoltaic output voltage fitting value under light intensity i; U mi is the actual value of the photovoltaic output maximum power point voltage under light intensity i; P mi is the actual maximum power output of the photovoltaic under light intensity i; K rel is the slope correction coefficient; When the voltage exceeds U mi After that, the power-voltage curve shows a downward trend, and the decline is large. A small voltage change will lead to a large power fluctuation, which will control the output voltage of the photovoltaic power generation system to be less than the maximum power point voltage value U mi .

4. The off-grid hydro-photovoltaic microgrid control method based on photovoltaic load reduction operation according to claim 1 is characterized in that: In step 2, the microgrid controller sets the photovoltaic power generation system to 0.45U under the current light intensity. mi Voltage load reduction operation, U mi It is the actual value of the photovoltaic output maximum power point voltage under light intensity i.

5. The off-grid hydro-photovoltaic microgrid control method based on photovoltaic load reduction operation according to claim 1 is characterized in that: Reference value of power generation of small hydropower station P hdref for: P hdref =P load -P pvi Among them, P load is the currently measured local load, P pvi is the fitted value of the photovoltaic output power under light intensity i.

6. The off-grid hydro-photovoltaic microgrid control method based on photovoltaic load reduction operation according to claim 1 is characterized in that: In step 3, the current microgrid system frequency f and the frequency change rate df / dt are judged, and the power generation of the photovoltaic power generation system and the small hydropower station power generation system is adjusted, specifically including: When 49.8≤f≤50.2, maintain the current operation status of the photovoltaic power generation system and the small hydropower station power generation system; When f>50.2, judge df / dt: When df / dt≥0, the photovoltaic power generation system is adjusted to operate with the calculated maximum voltage difference ΔU1, that is, the reference voltage U pvref =U pv -ΔU1; U calculated after load reduction pvref <0, adjust the power generation system of small hydropower stations to reduce power generation; When df / dt<0, the photovoltaic power generation system operates with a constant voltage difference ΔU2, that is, the reference voltage U pvref =U pv -ΔU2; When f<49.8, judge df / dt: When df / dt≤0, the photovoltaic power generation system operates with the calculated maximum voltage difference ΔU1, that is, the reference voltage U pvref =U pv -ΔU1; When (dP pv / dU pv )=0, the measured P pv is the maximum power of the photovoltaic power generation unit under the current working conditions, and the measured U pv The maximum power point voltage value of the photovoltaic power generation unit is used to update the data in the data table with the maximum power point voltage value and power value of the current light intensity. At the same time, in order to make the photovoltaic power generation unit always run on the left side of the maximum power point, the power generation system of the small hydropower station is adjusted to increase the power generation; When df / dt>0, the photovoltaic power generation system operates with a constant voltage difference ΔU2, that is, the reference voltage U pvref =U pv -ΔU2; Where P pv is the actual output power value of the photovoltaic power generation system measured under the current working conditions, U pv It is the actual value of the photovoltaic power generation system output voltage measured under the current working conditions.

7. The off-grid hydro-photovoltaic microgrid control method based on photovoltaic load reduction operation according to claim 6 is characterized in that the maximum voltage difference ΔU1 is: Where P hd is the currently measured power generation of the small hydropower station, I i is the slope of the power-voltage curve, P load is the currently measured local load.

8. The off-grid hydro-photovoltaic microgrid control method based on photovoltaic load reduction operation according to claim 6 is characterized in that the constant voltage difference ΔU2 is: In the formula, K j Is a positive integer.

9. The off-grid hydropower microgrid control method based on photovoltaic load reduction operation according to claim 6 is characterized in that the power generation of the small hydropower station is adjusted to increase the power generation or reduce the power generation P hdref for: P hdref =P load -0.45*P mi Where P load is the currently measured local load; P mi is the actual maximum power output of the photovoltaic under light intensity i; Synchronously set the reference voltage of the photovoltaic power generation system to: U pvref =0.45*U mi , U mi It is the actual value of the photovoltaic output maximum power point voltage under light intensity i.

10. The off-grid hydro-photovoltaic microgrid control method based on photovoltaic load shedding operation according to claim 6 is characterized in that when (dP pv / dU pv )=0, update the maximum power point voltage value and power value under the current working condition; According to the power voltage curve of the photovoltaic power generation unit, when (dP pv / dU pv )=0, the measured P pv is the maximum power of the photovoltaic power generation unit under the current working conditions, and the measured U pv The maximum power point voltage value of the photovoltaic power generation unit is used to update the data in the data table with the maximum power point voltage value and power value of the current light intensity.

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