Safety protection system based on new energy power supply access power grid system

Abstract

The invention relates to the technical field of safety protection of an access power grid, in particular to a safety protection system based on a new energy power supply access power grid system. The method comprises the steps that a tracking unit captures direct current generated by new energy power generation equipment and captures the optimal power generation efficiency through a perturbation and observation method; the grid-connected inverter unit converts the direct current transmitted by the tracking unit into alternating current through a PWM modulation method, and adjusts output power according to the demand of a power grid; and the intelligent monitoring unit monitors the alternating current transmitted by the grid-connected inverter unit and the state of the power grid. According to the design, effective tracking of the maximum power point is achieved through a perturbation and observation method, the method not only considers natural factors such as real-time illumination conditions and wind speed, but also introduces the photovoltaic panel aging rate and atmospheric transparency parameters, so that the system can be adjusted to the optimal power generation efficiency point more accurately, and the optimal power generation efficiency is achieved. Therefore, the utilization efficiency of new energy can be maximized, and energy waste is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of safety protection for accessing a power grid, and in particular to a safety protection system for accessing a power grid based on a new energy power source. Background Art

[0002] Renewable energy sources such as solar photovoltaic and wind power generation are intermittent and uncertain, which means that their output power will fluctuate with changes in weather and climate conditions. Such characteristics may lead to instability in grid voltage and frequency, affecting the overall stability and power supply quality of the power system; when the grid fails or is under maintenance, if distributed power sources (such as photovoltaic power stations) continue to supply power to local loads, a so-called "island" operating state may be formed. In this state, if not properly managed, it may cause harm to maintenance personnel or further damage to grid equipment. Therefore, a safety protection system based on the access of renewable energy power sources to the grid system is designed. Summary of the invention

[0003] The purpose of the present invention is to provide a safety protection system based on a new energy power supply access grid system to solve the problems of low power quality and stability, island effect and low maximum power tracking efficiency raised in the above background technology.

[0004] To achieve the above object, the present invention aims to provide a safety protection system based on a new energy power supply access power grid system, comprising:

[0005] A tracking unit, wherein the tracking unit captures the direct current generated by the new energy power generation equipment, captures the best power generation efficiency through a perturbation observation method, and introduces a photovoltaic panel aging rate and an atmospheric transparency parameter in the process of capturing the best power generation efficiency;

[0006] A grid-connected inverter unit, which converts the direct current transmitted by the tracking unit into alternating current through a PWM modulation method, and adjusts the output power according to the needs of the power grid;

[0007] An intelligent monitoring unit monitors the alternating current transmitted by the grid-connected inverter unit and the state of the grid.

[0008] As a further improvement of the present technical solution, the direct current generated by the new energy power generation equipment includes: solar direct current and wind direct current.

[0009] As a further improvement of the technical solution, capturing the optimal power generation efficiency by the perturbation observation method includes the following steps:

[0010] S1.1. Collect the voltage, current and power of direct current generated by new energy power generation equipment;

[0011] S1.2. Calculate the current-voltage output characteristics of the photovoltaic panel according to the current lighting conditions, and introduce the photovoltaic panel aging rate and atmospheric transparency parameters in the calculation process to improve the accuracy of the current-voltage output characteristic calculation. Calculate the power-voltage output characteristics of the wind turbine according to the wind speed conditions, and consider the influence of wind speed distribution, humidity, environmental pollution and electrical characteristics, and establish a multivariable model to optimize the calculation process of the power-voltage output characteristics.

[0012] S1.3, determine the maximum power point MPP under current conditions based on the analysis of current-voltage output characteristics and power-voltage output characteristics through the perturbation observation method;

[0013] S1.4, after finding the maximum power point, adjusting the voltage and current combination of the power conversion module to obtain the highest power generation efficiency under the current conditions;

[0014] S1.5. Continuously monitor the system status and adjust the operating parameters of the power conversion module accordingly to maintain operation near the maximum power point MPP.

[0015] As a further improvement of the technical solution, in S1.2, the current-voltage output characteristic of the photovoltaic panel is calculated according to the current lighting conditions as follows:

[0016] ;

[0017] The photovoltaic panel aging rate and atmospheric transparency parameters are introduced in the calculation process as follows:

[0018] ;

[0019] in, represents the output current of the photovoltaic cell at a given voltage 𝑉; Indicates the corrected short-circuit current; Indicates the voltage value across the photovoltaic cell; represents parallel resistance; represents the series resistance; Represents the reverse saturation current; Represents the amount of electron charge; represents the ideality factor of the diode; represents the Boltzmann constant; Indicates temperature; Indicates the atmospheric transparency parameter; Photovoltaic panels indicate aging rate.

[0020] As a further improvement of the technical solution, in S1.2, the current-voltage output characteristic of the wind turbine generator is calculated according to the wind speed conditions as follows:

[0021] ;

[0022] Considering the influence of wind speed distribution, humidity, environmental pollution and electrical characteristics, a multivariable model is established to optimize the calculation process of power-voltage output characteristics:

[0023] ;

[0024] in, represents the output power of the wind turbine at a given voltage 𝑉; Wind turbines at a specific wind speed , output voltage ,humidity , Environmental pollution Output power under the conditions; Indicates output power; Indicates the output voltage; is the proportionality constant; is an index; represents the coefficient related to wind speed; Indicates coefficients related to electrical characteristics; Indicates the maximum humidity impact threshold; represents the maximum pollution impact threshold; Power factor; Indicates current; Indicates humidity; Indicates environmental pollution; Indicates wind speed.

[0025] As a further improvement of the technical solution, in S1.3, the maximum power point MPP under the current conditions is determined based on the analysis of the current-voltage output characteristics and the power-voltage output characteristics by the perturbation observation method, including the following steps:

[0026] S1.31, select an initial operating point, that is, the initial output voltage and current of the power generation module;

[0027] S1.32. Define a small disturbance , ;

[0028] S1.33, measure the output current at the current working point and voltage , thus calculating the current output power , ;

[0029] S1.34, add the disturbance value to the current working point, including increasing the output voltage, to get a new working point ;

[0030] S1.35, at the new working point Measure the new output current , and then calculate the new output power , ;

[0031] S1.36, the new output power Compared with the previous output power For comparison, if , it means the disturbance direction is correct. Continue to disturb in this direction. Updated to ,if , it means that the disturbance direction is wrong and reverse disturbance is needed. Change to ;

[0032] S1.37. The maximum power point MPP is obtained after there is no significant change in power after several consecutive disturbances.

[0033] As a further improvement of the technical solution, the direct current transmitted by the tracking unit is converted into alternating current through a PWM modulation method, comprising the following steps:

[0034] S2.1. The inverter uses a phase-locked loop method to detect the frequency and phase of the power grid to ensure that the output AC power is synchronized with the power grid. According to the frequency and phase information of the power grid, the required AC power phase and voltage are calculated;

[0035] S2.2, generating a corresponding PWM signal according to the calculated AC phase and voltage;

[0036] S2.3, the power switch module switches according to the PWM signal to convert DC power into AC power;

[0037] As a further improvement of the technical solution, the intelligent monitoring unit includes a voltage and frequency monitoring module and an island monitoring module;

[0038] Among them, the voltage and frequency monitoring module is used to monitor whether the voltage level and frequency of the AC power output by the grid-connected inverter unit meet the standard requirements of the power grid;

[0039] The island monitoring module detects the failure of the main power grid through the voltage / frequency change rate and disconnects from the power grid in time when the main power grid fails.

[0040] As a further improvement of the technical solution, the monitoring of whether the voltage level and frequency of the AC power output by the grid-connected inverter unit meets the standard requirements of the power grid includes the following steps:

[0041] S3.1. Collect the specific values ​​of the voltage and frequency of the AC power output by the grid-connected inverter unit;

[0042] S3.2, comparing the collected voltage and frequency values ​​with the prescribed standards of the power grid;

[0043] S3.3. Determine whether these values ​​are within the allowable deviation range, which is: ±5% voltage fluctuation and ±0.5Hz frequency fluctuation;

[0044] S3.4. If it is found that the voltage and frequency deviate from the standard value, the output of the grid-connected inverter unit is adjusted through the feedback control module to return it to the normal range.

[0045] As a further improvement of the technical solution, the voltage / frequency change rate detection includes the following steps:

[0046] S4.1. Monitor the voltage and frequency values ​​of the power grid and calculate the rate of change of the voltage and frequency values ​​over time;

[0047] S4.2, setting the threshold value m of the voltage change rate and the threshold value n of the frequency change rate;

[0048] S4.3, when it is detected that the actual change rate of voltage and frequency exceeds the preset threshold, the island monitoring module will consider that an island phenomenon has occurred;

[0049] S4.4. If it is determined that the change rate exceeds the set threshold and the islanding state is confirmed, the islanding monitoring module will immediately trigger a protection action, which includes disconnecting the connection between the grid-connected inverter unit and the grid.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1. In the security protection system based on the access of new energy power to the power grid system, the maximum power point (MPP) is effectively tracked through the perturbation observation method. This method not only takes into account natural factors such as real-time lighting conditions and wind speed, but also introduces the aging rate of photovoltaic panels and atmospheric transparency parameters, so that the system can be more accurately adjusted to the optimal power generation efficiency point. This not only helps to maximize the utilization efficiency of new energy and reduce energy waste, but also enhances the system's ability to adapt to environmental changes and ensures the stability and reliability of energy supply.

[0052] 2. In the safety protection system based on the access of new energy power to the grid system, the existence of the intelligent monitoring unit ensures that the AC power output by the grid-connected inverter unit meets the grid standard requirements and can respond quickly when a fault occurs in the main grid. The voltage and frequency monitoring modules continuously monitor the power quality, while the island monitoring module can quickly detect and disconnect when an abnormality occurs in the grid, avoiding potential safety hazards. This design greatly improves the safety of the entire system, reduces losses caused by power instability or failures, and ensures the stable operation of the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is the overall flow chart of the present invention;

[0054] The meaning of each number in the figure is:

[0055] 1. Tracking unit; 2. Grid-connected inverter unit; 3. Intelligent monitoring unit. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] See also Figure 1 As shown, a safety protection system based on the access of new energy power to the power grid system is provided, including:

[0058] Tracking unit 1 captures the direct current generated by the renewable energy power generation equipment and captures the best power generation efficiency through the perturbation observation method;

[0059] In this embodiment, the direct current generated by the new energy power generation equipment includes: solar direct current and wind direct current.

[0060] Among them, the perturbation observation method uses continuous small-amplitude perturbations to find the optimal working point. Once the power increase is detected, it will continue to adjust in this direction, otherwise it will change direction. Therefore, under rapidly changing conditions, it can converge to the maximum power point quickly; the perturbation observation method is highly robust to changes in system parameters. Even when the parameters are unknown or change over time, as long as the perturbation is small enough and the frequency is moderate, the system can still effectively track the maximum power point; the size and frequency of the perturbation can be adjusted according to different application scenarios. For example, in an environment where the light changes slowly, a larger perturbation step size and a longer period can be used to improve the tracking efficiency; in a scenario where the light changes quickly, a smaller step size and a shorter period can be used to enhance the precision of the tracking; capturing the best power generation efficiency through the perturbation observation method includes the following steps:

[0061] S1.1. Collect the voltage, current and power of direct current generated by new energy power generation equipment;

[0062] S1.2. Calculate the current-voltage output characteristics of the photovoltaic panel according to the current lighting conditions, and introduce the photovoltaic panel aging rate and atmospheric transparency parameters in the calculation process to improve the accuracy of the current-voltage output characteristic calculation. Calculate the power-voltage output characteristics of the wind turbine according to the wind speed conditions, and consider the influence of wind speed distribution, humidity, environmental pollution and electrical characteristics, and establish a multivariable model to optimize the calculation process of the power-voltage output characteristics.

[0063] Furthermore, the current-voltage output characteristics of the photovoltaic panel are calculated based on the current lighting conditions as follows:

[0064] ;

[0065] The aging rate of photovoltaic panels and the atmospheric transparency parameters directly affect the output performance of photovoltaic panels. Over time, the efficiency of photovoltaic panels will gradually decrease due to the natural degradation of materials and environmental factors. At the same time, changes in atmospheric transparency (for example, due to clouds, pollution, etc.) will affect the amount of solar radiation reaching the surface of photovoltaic panels. By introducing these parameters, the output performance of photovoltaic panels under specific conditions can be more accurately predicted, thereby improving the effect of the maximum power point tracking (MPPT) algorithm; the introduction of these parameters enables the system to better adapt to different operating environments. Whether in cities or rural areas, whether on sunny or cloudy days, the system can adjust its operating strategy according to actual conditions to ensure that high power generation efficiency can be achieved under various conditions. The specific parameters of photovoltaic panel aging rate and atmospheric transparency are introduced in the calculation process as follows:

[0066] ;

[0067] in, represents the output current of the photovoltaic cell at a given voltage 𝑉, which is the current output value of the photovoltaic cell at different operating points; represents the corrected short-circuit current, which is the current output value when there is no external load at both ends of the photovoltaic cell (that is, the voltage is zero) under light intensity 𝐺. Correction means that the influence of current light intensity and temperature is taken into account; Indicates the voltage value across the photovoltaic cell; Indicates parallel resistance, reflecting the leakage inside the battery; represents the series resistance, reflecting the internal loss of the battery; Reverse saturation current, which is the dark current of a photovoltaic cell in the absence of light, is usually very small and reflects the current of the diode when it is reverse biased; Represents the amount of electron charge; represents the ideality factor of the diode, which is between 1 and 2; represents the Boltzmann constant; Indicates temperature; It represents the atmospheric transparency parameter, which reflects the transparency of the atmosphere to solar radiation; The PV panel indicates the aging rate, which represents the percentage of efficiency decline of the PV panel relative to the new state;

[0068] Furthermore, the current-voltage output characteristic of the wind turbine generator is calculated according to the wind speed conditions as follows:

[0069] ;

[0070] Different wind speed distribution patterns can affect the design and operating efficiency of wind turbines. For example, frequent wind speed changes may cause increased mechanical stress and affect the life of the equipment. Humidity can affect air density, which can indirectly affect the performance of wind turbines. The greater the air density, the greater the resistance to the wind turbine blades, and theoretically more energy can be generated. Pollutants in the air (such as dust, salt spray, industrial emissions, etc.) may be deposited on the blades of wind turbines, affecting their aerodynamic performance and thus reducing power generation efficiency. Electrical characteristics mainly include voltage, current, frequency, power factor, etc. These parameters directly affect the output quality and stability of wind turbines. Multivariate models can better reflect the complex and changeable operating conditions in the real world. Since factors such as wind speed distribution, humidity and environmental pollution change with time and location, a model that can adapt to these changes can make the wind power generation system more flexible to respond to different environmental conditions and improve the overall adaptability and reliability of the system. Considering the influence of wind speed distribution, humidity, environmental pollution and electrical characteristics, the calculation process of establishing a multivariate model for optimizing the calculation of power-voltage output characteristics is as follows:

[0071] ;

[0072] in, represents the output power of the wind turbine at a given voltage 𝑉; Wind turbines at a specific wind speed , output voltage ,humidity , Environmental pollution Output power under the conditions; Indicates output power; Indicates the output voltage; It is a proportional constant, which includes factors such as air density, wind wheel area, and wind energy utilization coefficient; It is an exponential, usually greater than 1, indicating the nonlinear relationship between power and voltage; represents the coefficient related to wind speed; Indicates coefficients related to electrical characteristics; Indicates the maximum humidity impact threshold; represents the maximum pollution impact threshold; Power factor; Indicates current; Indicates humidity; Indicates environmental pollution; Indicates wind speed;

[0073] S1.3, determine the maximum power point MPP under current conditions based on the analysis of current-voltage output characteristics and power-voltage output characteristics through the perturbation observation method;

[0074] The maximum power point MPP under current conditions is determined by the perturbation observation method based on the analysis of the current-voltage output characteristics and the power-voltage output characteristics, including the following steps:

[0075] S1.31. Select an initial operating point, i.e., the initial output voltage and current of a power generation module, where the power generation module represents a photovoltaic array;

[0076] S1.32. Define a small disturbance , ;

[0077] S1.33, measure the output current at the current working point and voltage , thus calculating the current output power , ;

[0078] S1.34, add the disturbance value to the current working point, including increasing the output voltage, to get a new working point ;

[0079] S1.35, at the new working point Measure the new output current , and then calculate the new output power , ;

[0080] S1.36, the new output power Compared with the previous output power For comparison, if , it means the disturbance direction is correct. Continue to disturb in this direction. Updated to ,if , it means that the disturbance direction is wrong and reverse disturbance is needed. Change to As the system approaches the maximum power point MPP, the disturbance can be gradually reduced. , used to improve tracking accuracy;

[0081] S1.37. The maximum power point MPP is obtained after there is no significant change in power after several consecutive disturbances.

[0082] S1.4, after finding the maximum power point, adjusting the voltage and current combination of the power conversion module to obtain the highest power generation efficiency under the current conditions, wherein the power conversion module represents a DC-DC converter;

[0083] S1.5. Continuously monitor the system status and adjust the operating parameters of the power conversion module accordingly to maintain operation near the maximum power point MPP.

[0084] The grid-connected inverter unit 2 converts the DC power transmitted by the tracking unit 1 into AC power through the PWM modulation method, and adjusts the output power according to the needs of the power grid;

[0085] In this embodiment, the PWM modulation method allows the inverter to operate at a high frequency, and by quickly switching the power switch (such as IGBT or MOSFET), high-efficiency energy conversion can be achieved with low switching losses. This method reduces the loss of energy during the conversion process and improves the energy efficiency of the overall system; the PWM modulation method can adjust the amplitude of the output voltage by changing the pulse width, thereby achieving precise control of the AC waveform. This means that the inverter can adjust the output power according to the needs of the power grid, ensure that the output voltage and frequency are synchronized with the power grid, and improve the power quality; the PWM modulation method provides a fast dynamic response capability and can quickly adapt to changes in the power grid or load. This is especially important for dealing with rapidly changing loads or power grid fluctuations, and helps to maintain stable operation of the system; the DC power transmitted by the tracking unit 1 is converted into AC power through the PWM modulation method, including the following steps:

[0086] S2.1. The inverter uses a phase-locked loop method to detect the frequency and phase of the power grid to ensure that the output AC power is synchronized with the power grid. According to the frequency and phase information of the power grid, the required AC power phase and voltage are calculated to ensure that the power output by the inverter is synchronized with the power grid.

[0087] S2.2, generating a corresponding PWM signal according to the calculated AC phase and voltage;

[0088] S2.3, the power switch module switches according to the PWM signal to convert the direct current into alternating current, and adjusts the power control parameters based on the received information, including changing the duty cycle of the PWM modulation, controlling the on-time of the power switch module, thereby adjusting the output alternating current power, wherein the power switch module represents a power switch;

[0089] Furthermore, when the PWM signal is at a high level, the corresponding power switch will be turned on, so that the DC power flows to the load or the grid through the switch, forming a current path;

[0090] When the PWM signal is at a low level, the corresponding power switch will be turned off, cutting off the path for current to flow through the switch.

[0091] The intelligent monitoring unit 3 monitors the AC power transmitted by the grid-connected inverter unit 2 and the state of the grid;

[0092] In this embodiment, the intelligent monitoring unit 3 includes a voltage and frequency monitoring module and an island monitoring module;

[0093] The voltage and frequency monitoring module is used to monitor whether the voltage level and frequency of the AC power output by the grid-connected inverter unit 2 meet the standard requirements of the power grid;

[0094] Furthermore, voltage and frequency that do not meet the standards may cause damage to all devices connected to the power grid. For example, excessive voltage may cause electrical appliances to overheat or burn, and unstable frequency may affect the speed of the motor, affecting the normal production and life. The monitoring function helps to detect these problems in time and take corrective measures; monitoring whether the voltage level and frequency of the AC power output by the grid-connected inverter unit 2 meet the standard requirements of the power grid includes the following steps:

[0095] S3.1. Collect the specific values ​​of the voltage and frequency of the AC power output by the grid-connected inverter unit 2;

[0096] S3.2, comparing the collected voltage and frequency values ​​with the prescribed standards of the power grid;

[0097] S3.3. Determine whether these values ​​are within the allowable deviation range, which is: ±5% voltage fluctuation and ±0.5Hz frequency fluctuation;

[0098] S3.4, if it is found that the voltage and frequency deviate from the standard value, the output of the grid-connected inverter unit 2 is adjusted through the feedback control module to return it to the normal range, wherein the feedback control module represents an integral differential (PID) controller;

[0099] The island monitoring module detects the failure of the main grid through the voltage / frequency change rate and disconnects from the grid in time when the main grid fails;

[0100] Among them, when the main power grid fails, if the distributed power source (such as a solar photovoltaic system or a wind power generation system) continues to supply power to the grid, the so-called "island effect" may be formed. The power supply in the island state may cause electric shock hazards to the staff who are repairing the power grid. This risk can be effectively avoided by detecting the rate of change of voltage and frequency and quickly disconnecting when an abnormality is detected; large fluctuations in voltage and frequency can cause damage to power equipment. If the distributed power source fails to disconnect in time during a power grid failure, its output power may interact with the rest of the power grid, resulting in voltage and frequency instability, thereby damaging the equipment connected to the power grid. By disconnecting in time, these devices can be protected from damage; voltage / frequency change rate detection includes the following steps:

[0101] S4.1. Monitor the voltage and frequency values ​​of the power grid and calculate the rate of change of the voltage and frequency values ​​over time. The rate of change of the voltage and frequency is calculated by dividing the difference between consecutive sampling points by the time interval;

[0102] If in time and The voltages measured at and , then the rate of change of voltage for: , represents the time interval between two measurements;

[0103] If in time and The voltages measured at and , then the rate of change of frequency for: , represents the time interval between two measurements;

[0104] S4.2, setting a voltage change rate threshold m and a frequency change rate threshold n, which represent the maximum allowable rates of voltage and frequency change under normal operating conditions;

[0105] S4.3, when it is detected that the actual change rate of voltage and frequency exceeds the preset threshold, the island monitoring module will consider that an island phenomenon has occurred;

[0106] S4.4. If it is determined that the change rate exceeds the set threshold and the island state is confirmed, the island monitoring module will immediately trigger a protection action, which includes disconnecting the connection between the grid-connected inverter unit 2 and the grid to prevent the power in the island state from continuing to flow into the grid.

[0107] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only preferred examples of the present invention, and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A safety protection system based on the access of new energy power to the power grid system, characterized in that: include: A tracking unit (1), wherein the tracking unit (1) captures the direct current generated by the new energy power generation equipment, captures the optimal power generation efficiency through a perturbation observation method, and introduces a photovoltaic panel aging rate and an atmospheric transparency parameter in the process of capturing the optimal power generation efficiency; A grid-connected inverter unit (2), wherein the grid-connected inverter unit (2) converts the direct current transmitted by the tracking unit (1) into alternating current through a PWM modulation method, and adjusts the output power according to the needs of the power grid; An intelligent monitoring unit (3), wherein the intelligent monitoring unit (3) monitors the alternating current transmitted by the grid-connected inverter unit (2) and the state of the grid.

2. The safety protection system based on the new energy power supply access to the power grid system according to claim 1 is characterized in that: The direct current generated by the new energy power generation equipment includes: solar direct current and wind direct current.

3. The safety protection system based on the new energy power supply access to the power grid system according to claim 1 is characterized in that: The method of capturing the best power generation efficiency by the perturbation observation method comprises the following steps: S1.

1. Collect the voltage, current and power of direct current generated by new energy power generation equipment; S1.

2. Calculate the current-voltage output characteristics of the photovoltaic panel according to the current lighting conditions, and introduce the photovoltaic panel aging rate and atmospheric transparency parameters in the calculation process to improve the accuracy of the current-voltage output characteristic calculation. Calculate the power-voltage output characteristics of the wind turbine according to the wind speed conditions, and consider the influence of wind speed distribution, humidity, environmental pollution and electrical characteristics, and establish a multivariable model to optimize the calculation process of the power-voltage output characteristics. S1.3, determine the maximum power point MPP under current conditions based on the analysis of current-voltage output characteristics and power-voltage output characteristics through the perturbation observation method; S1.4, after finding the maximum power point, adjusting the voltage and current combination of the power conversion module to obtain the highest power generation efficiency under the current conditions; S1.

5. Continuously monitor the system status and adjust the operating parameters of the power conversion module accordingly to maintain operation near the maximum power point MPP.

4. The safety protection system based on the new energy power supply access to the power grid system according to claim 3 is characterized in that: In S1.2, the current-voltage output characteristics of the photovoltaic panel are calculated according to the current lighting conditions as follows: ； The photovoltaic panel aging rate and atmospheric transparency parameters are introduced in the calculation process as follows: ； in, represents the output current of the photovoltaic cell at a given voltage 𝑉; Indicates the corrected short-circuit current; Indicates the voltage value across the photovoltaic cell; represents parallel resistance; represents the series resistance; Represents the reverse saturation current; Represents the amount of electron charge; represents the ideality factor of the diode; represents the Boltzmann constant; Indicates temperature; Indicates the atmospheric transparency parameter; Photovoltaic panels indicate aging rate.

5. The safety protection system based on the new energy power supply access to the power grid system according to claim 3 is characterized in that: In S1.2, the current-voltage output characteristic of the wind turbine generator is calculated according to the wind speed conditions as follows: ； Considering the influence of wind speed distribution, humidity, environmental pollution and electrical characteristics, a multivariable model is established to optimize the calculation process of power-voltage output characteristics: ； in, represents the output power of the wind turbine at a given voltage 𝑉; Wind turbines at a specific wind speed , output voltage ,humidity , Environmental pollution Output power under the conditions; Indicates output power; Indicates the output voltage; is the proportionality constant; is an index; represents the coefficient related to wind speed; Indicates coefficients related to electrical characteristics; Indicates the maximum humidity impact threshold; represents the maximum pollution impact threshold; Power factor; Indicates current; Indicates humidity; Indicates environmental pollution; Indicates wind speed.

6. The safety protection system based on the new energy power supply access to the power grid system according to claim 3 is characterized in that: In S1.3, the maximum power point MPP under current conditions is determined by the perturbation observation method based on the analysis of the current-voltage output characteristics and the power-voltage output characteristics, including the following steps: S1.31, select an initial operating point, that is, the initial output voltage and current of the power generation module; S1.

32. Define a small disturbance , ; S1.33, measure the output current at the current working point and voltage , thus calculating the current output power , ; S1.34, add the disturbance value to the current working point, including increasing the output voltage, to get a new working point ; S1.35, at the new working point Measure the new output current , and then calculate the new output power , ; S1.36, the new output power Compared with the previous output power For comparison, if , it means the disturbance direction is correct. Continue to disturb in this direction. Updated to ,if , it means that the disturbance direction is wrong and reverse disturbance is needed. Change to ; S1.

37. The maximum power point MPP is obtained after there is no significant change in power after several consecutive disturbances.

7. The safety protection system based on the new energy power supply access to the power grid system according to claim 1 is characterized in that: The method of converting the direct current transmitted by the tracking unit (1) into alternating current by means of a PWM modulation method comprises the following steps: S2.

1. The inverter uses a phase-locked loop method to detect the frequency and phase of the power grid to ensure that the output AC power is synchronized with the power grid. According to the frequency and phase information of the power grid, the required AC power phase and voltage are calculated; S2.2, generating a corresponding PWM signal according to the calculated AC phase and voltage; S2.3, the power switch module switches according to the PWM signal to convert DC power into AC power.

8. The safety protection system based on the new energy power supply access to the power grid system according to claim 1 is characterized in that: The intelligent monitoring unit (3) comprises a voltage and frequency monitoring module and an island monitoring module; The voltage and frequency monitoring module is used to monitor whether the voltage level and frequency of the alternating current output by the grid-connected inverter unit (2) meet the standard requirements of the grid; The island monitoring module detects the failure of the main power grid through the voltage / frequency change rate and disconnects from the power grid in time when the main power grid fails.

9. The safety protection system based on the new energy power supply access to the power grid system according to claim 8 is characterized in that: The monitoring of whether the voltage level and frequency of the alternating current output by the grid-connected inverter unit (2) meet the standard requirements of the power grid comprises the following steps: S3.

1. Collect specific values ​​of voltage and frequency of the alternating current output by the grid-connected inverter unit (2); S3.2, comparing the collected voltage and frequency values ​​with the prescribed standards of the power grid; S3.

3. Determine whether these values ​​are within the allowable deviation range, which is: ±5% voltage fluctuation and ±0.5Hz frequency fluctuation; S3.

4. If it is found that the voltage and frequency deviate from the standard value, the output of the grid-connected inverter unit (2) is adjusted through the feedback control module to return it to the normal range.

10. The safety protection system based on the new energy power supply access to the power grid system according to claim 8 is characterized in that: The voltage / frequency change rate detection includes the following steps: S4.

1. Monitor the voltage and frequency values ​​of the power grid and calculate the rate of change of the voltage and frequency values ​​over time; S4.2, setting the threshold value m of the voltage change rate and the threshold value n of the frequency change rate; S4.3, when it is detected that the actual change rate of voltage and frequency exceeds the preset threshold, the island monitoring module will consider that an island phenomenon has occurred; S4.

4. If it is determined that the change rate exceeds the set threshold and the islanding state is confirmed, the islanding monitoring module will immediately trigger a protection action, which includes disconnecting the connection between the grid-connected inverter unit (2) and the grid.

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