Maximum power point tracking method and system, inverter and storage medium

Abstract

The application provides a maximum power point tracking method and system, an inverter and a storage medium. The maximum power point tracking method comprises the following steps: collecting an initial input voltage of a photovoltaic module; determining a reference voltage and a perturbation step according to the initial input voltage; taking the reference voltage as a median value, determining three working points according to the perturbation step, and collecting output powers of the three working points, wherein the three working points are a low-voltage working point, a medium-voltage working point and a high-voltage working point; determining a perturbation direction of the reference voltage and adjusting the perturbation step according to the size relationship among the output powers of the three working points; when the adjusted perturbation step is less than or equal to a preset step threshold, calculating a voltage of a theoretical maximum power point through a quadratic interpolation formula according to the voltages and the output powers of the three working points; and outputting the voltage of the theoretical maximum power point as an updated reference voltage. The application can effectively reduce power generation energy loss.

Description

Technical Field

[0001] This invention relates to the field of energy storage equipment technology, and more specifically, to a maximum power point tracking method and system, an inverter, and a storage medium. Background Technology

[0002] In photovoltaic (PV) power generation systems, Maximum Power Point Tracking (MPPT) is a core control technology for improving the power generation efficiency of PV modules. This technology adjusts the operating voltage of the PV converter in real time to keep the PV module operating at its maximum power point (MPP). Most existing conventional MPPT algorithms are adapted to low-voltage, narrow-voltage PV scenarios, generally employing a fixed, small perturbation step size. Under these conditions, the difference between the actual operating voltage and the maximum power point voltage is small, and power changes are gradual, achieving a tracking efficiency of over 99.9%. However, if this fixed-step MPPT scheme is directly applied to 30V~450V high-voltage, wide-range PV systems, the fixed step size limits the convergence speed during long-distance voltage optimization. This results in a significant deviation between the actual operating point and the true maximum power point, causing substantial power loss and ultimately drastically reducing the overall MPPT tracking efficiency. Summary of the Invention

[0003] The present invention aims to solve the technical problems existing in the prior art or related technologies.

[0004] Therefore, the first aspect of the present invention proposes a maximum power point tracking method.

[0005] A second aspect of the invention proposes a maximum power point tracking system.

[0006] A third aspect of the present invention provides an inverter.

[0007] A fourth aspect of the present invention provides a storage medium.

[0008] In view of this, according to a first aspect of the present invention, a maximum power point tracking (MPPT) method is proposed, wherein the MPPT method includes: acquiring the initial input voltage of a photovoltaic module; determining a reference voltage and a perturbation step size based on the initial input voltage; determining three operating points according to the perturbation step size, using the reference voltage as the median, and acquiring the output power of the three operating points respectively, wherein the three operating points are: a low-voltage operating point, a medium-voltage operating point, and a high-voltage operating point; determining the perturbation direction of the reference voltage based on the magnitude relationship between the output power of the three operating points, and adjusting the perturbation step size; when the adjusted perturbation step size is less than or equal to a preset step size threshold, calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage and output power of the three operating points; and outputting the voltage of the theoretical maximum power point as the updated reference voltage.

[0009] The maximum power point tracking (MPPT) method provided by this invention mainly includes: First, acquiring the initial input voltage (open-circuit voltage) of the photovoltaic module. Then, determining a reference voltage and a perturbation step size based on the initial input voltage. The reference voltage can be 80% of the initial input voltage, and the perturbation step size can be 5% of the initial input voltage. The reference voltage is the target control voltage of the photovoltaic converter and also the output control quantity of the MPPT algorithm. The perturbation step size refers to the voltage interval for each adjustment of the reference voltage, supporting dynamic amplification and reduction. After obtaining the reference voltage and perturbation step size, three operating points are determined according to the perturbation step size, using the reference voltage as the median. The output power of each of the three operating points is acquired, namely, the low-voltage operating point, the medium-voltage operating point, and the high-voltage operating point. Then, the relationship between the output power of the three operating points is compared, and the perturbation direction of the reference voltage is determined based on this relationship. The perturbation step size is adjusted synchronously. The perturbation direction refers to the adjustment offset direction of the reference voltage, which is divided into a low-voltage direction and a high-voltage direction. The low-voltage direction refers to decreasing the reference voltage according to the perturbation step size, and the high-voltage direction refers to increasing the reference voltage according to the perturbation step size. After determining the direction of the disturbance, the reference voltage is adjusted according to the direction of the disturbance. Based on the adjusted reference voltage and the adjusted disturbance step size, the three operating points and the output power of the three operating points are re-determined. Based on the output power of the three operating points, the reference voltage and the disturbance step size are readjusted. This process is repeated until the adjusted disturbance step size is less than or equal to the preset step size threshold.

[0010] When the adjusted perturbation step size is less than or equal to the preset step size threshold, the theoretical maximum power point voltage is calculated using a quadratic interpolation formula based on the voltage and output power of the three operating points corresponding to the adjusted perturbation step size. This involves fitting a photovoltaic power-voltage (PU) parabolic curve using the voltage and output power of the three operating points, and directly solving for the vertex of the parabola through the slope at two points, thus obtaining the theoretical maximum power point voltage. Finally, the calculated theoretical maximum power point voltage is assigned as the updated reference voltage and output as the voltage control target of the photovoltaic converter. This scheme first collects the initial photovoltaic input voltage to generate a reference voltage and perturbation step size. It achieves a coarse search with variable step size by sampling and comparing power at low, medium, and high voltage points. Under a wide range of operating conditions, it can quickly narrow down the voltage range of the MPP, significantly shortening the convergence time for long-distance optimization and avoiding large deviations between the operating voltage and the true maximum power point. When the perturbation step size is reduced to the threshold, it switches to a quadratic interpolation fine calculation mode, accurately solving for the theoretical maximum power point voltage without continuous repetitive perturbation, eliminating steady-state power fluctuation losses. Compared to traditional fixed small step size algorithms, this invention is adapted to high voltage wide voltage photovoltaic scenarios of 30V~450V, which not only ensures long-distance tracking speed, but also eliminates steady-state power oscillation, effectively reduces power generation energy loss, and stably maintains a high MPPT tracking efficiency of over 99.9%.

[0011] In some technical solutions, optionally, the step of determining the disturbance direction of the reference voltage based on the magnitude relationship between the output power of the three operating points and adjusting the disturbance step size includes: if the output power of the medium-voltage operating point is at its maximum value, then the disturbance step size is reduced according to a first preset rule; if the output power of the low-voltage operating point is at its maximum value, then the disturbance direction is determined to be the low-voltage direction, the reference voltage is disturbed in the low-voltage direction by one disturbance step size, and then the disturbance step size is increased according to a second preset rule; if the output power of the high-voltage operating point is at its maximum value, then the disturbance direction is determined to be the high-voltage direction, the reference voltage is disturbed in the high-voltage direction by one disturbance step size, and then the disturbance step size is increased according to a second preset rule.

[0012] In some technical solutions, optionally, the first preset rule is to multiply the perturbation step size by a preset coefficient, and the second preset rule is to divide the perturbation step size by a preset coefficient, wherein the preset coefficient is less than 1.

[0013] In some technical solutions, optionally, the step of calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage and output power of the three operating points includes: constructing a first curve based on the voltage of the low-voltage operating point, the output power of the low-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and calculating the first slope of the first curve; constructing a second curve based on the voltage of the high-voltage operating point, the output power of the high-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and calculating the second slope of the second curve; and calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage of the low-voltage operating point, the voltage of the medium-voltage operating point, the voltage of the high-voltage operating point, the first slope, and the second slope.

[0014] In some technical solutions, optionally, after the step of using the voltage of the theoretical maximum power point as the updated reference voltage output, the maximum power point tracking method further includes: updating the three operating points according to the magnitude between the voltage of the theoretical maximum power point and the voltage of the medium-voltage operating point; recalculating the voltage of the theoretical maximum power point according to the updated voltages of the three operating points and the output power, and re-outputting the updated voltage of the theoretical maximum power point as the updated reference voltage.

[0015] In some technical solutions, optionally, the step of updating the three operating points based on the difference between the voltage of the theoretical maximum power point and the voltage of the intermediate voltage operating point includes: if the voltage of the theoretical maximum power point is less than the voltage of the intermediate voltage operating point, then the original intermediate voltage operating point is taken as the new high voltage operating point, and the theoretical maximum power point is taken as the new intermediate voltage operating point; if the voltage of the theoretical maximum power point is greater than the voltage of the intermediate voltage operating point, then the original intermediate voltage operating point is taken as the new low voltage operating point, and the theoretical maximum power point is taken as the new intermediate voltage operating point.

[0016] In some technical solutions, optionally, after calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage and output power of the three operating points, the maximum power point tracking method further includes: if the output power of the theoretical maximum power point is less than the output power of any one of the three operating points, then the voltage of the theoretical maximum power point is used as the median, and the three operating points are re-determined according to the current perturbation step size.

[0017] According to a second aspect of the present invention, a maximum power point tracking (MPPT) system is proposed, comprising: a first processing module for acquiring the initial input voltage of a photovoltaic module and determining a reference voltage and a perturbation step size based on the initial input voltage; a second processing module for determining three operating points based on the reference voltage as the median and the perturbation step size, and acquiring the output power of the three operating points respectively, wherein the three operating points are: a low-voltage operating point, a medium-voltage operating point, and a high-voltage operating point; a third processing module for determining the perturbation direction of the reference voltage based on the relationship between the output power of the three operating points and adjusting the perturbation step size; a fourth processing module for calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage and output power of the three operating points when the adjusted perturbation step size is less than or equal to a preset step size threshold; and a fifth processing module for outputting the voltage of the theoretical maximum power point as an updated reference voltage.

[0018] The maximum power point tracking (MPPT) system provided by this invention mainly includes: a first processing module, a second processing module, a third processing module, a fourth processing module, and a fifth processing module. The first processing module first acquires the initial input voltage (open-circuit voltage) of the photovoltaic module. Then, based on the initial input voltage, it determines a reference voltage and a perturbation step size. The reference voltage can be 80% of the initial input voltage, and the perturbation step size can be 5% of the initial input voltage. The reference voltage is the target control voltage of the photovoltaic converter and also the output control quantity of the MPPT algorithm. The perturbation step size refers to the voltage interval for each adjustment of the reference voltage, supporting dynamic amplification and reduction. After obtaining the reference voltage and perturbation step size, the second processing module uses the reference voltage as the median and determines three operating points according to the perturbation step size, and acquires the output power of each of the three operating points, which are the low-voltage operating point, the medium-voltage operating point, and the high-voltage operating point, respectively. The third processing module then compares the output power of the three operating points to determine the perturbation direction of the reference voltage and adjusts the perturbation step size accordingly. The perturbation direction refers to the adjustment offset direction of the reference voltage, which is divided into a low-voltage direction and a high-voltage direction. The low-voltage direction involves decreasing the reference voltage according to the perturbation step size, while the high-voltage direction involves increasing the reference voltage according to the perturbation step size. After determining the perturbation direction, the reference voltage is adjusted accordingly. Based on the adjusted reference voltage and the adjusted perturbation step size, the three operating points and their output power are redefined. The reference voltage and perturbation step size are then readjusted based on the output power of the three operating points. This process is repeated until the adjusted perturbation step size is less than or equal to a preset step size threshold.

[0019] When the adjusted perturbation step size is less than or equal to the preset step size threshold, the fourth processing module uses a quadratic interpolation formula to calculate the theoretical maximum power point voltage based on the voltage and output power of the three operating points corresponding to the adjusted perturbation step size. This involves fitting the photovoltaic power unit (PU) parabolic curve using the voltage and output power of the three operating points, and directly solving for the vertex of the parabola through the slope at two points, thus obtaining the theoretical maximum power point voltage. Finally, the fifth processing module assigns the calculated theoretical maximum power point voltage as the updated reference voltage and outputs it as the voltage control target of the photovoltaic converter. This scheme first collects the initial photovoltaic input voltage to generate a reference voltage and perturbation step size. It achieves a coarse search with variable step size by sampling and comparing power at low, medium, and high voltage points. Under a wide range of operating conditions, it can quickly narrow down the voltage range where the MPP (Maximum Power Point) is located, significantly shortening the convergence time for long-distance optimization and avoiding large deviations between the operating voltage and the true maximum power point. When the perturbation step size is reduced to the threshold, it switches to a quadratic interpolation fine calculation mode, accurately solving for the theoretical maximum power point voltage without continuous repetitive perturbation, eliminating steady-state power fluctuation losses. Compared to traditional fixed small step size algorithms, this invention is adapted to high voltage wide voltage photovoltaic scenarios of 30V~450V, which not only ensures long-distance tracking speed, but also eliminates steady-state power oscillation, effectively reduces power generation energy loss, and stably maintains a high MPPT tracking efficiency of over 99.9%.

[0020] According to a third aspect of the invention, an inverter is proposed, comprising a maximum power point tracking system as described in any of the above-described technical solutions.

[0021] The inverter provided by this invention mainly includes a maximum power point tracking system as described in any of the above technical solutions, and can achieve the technical effects of any of the above technical solutions, which will not be elaborated here.

[0022] According to a fourth aspect of the invention, a storage medium is provided on which a computer program is stored, which, when executed by a processor, implements the steps of the maximum power point tracking method as described above.

[0023] The storage medium provided by this invention, when the computer program is executed by the processor, implements the steps of the above-described maximum power point tracking method, and can achieve the technical effects of any of the above technical solutions, which will not be elaborated here.

[0024] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0026] Figure 1One of the flowcharts of a maximum power point tracking method according to an embodiment of the present invention is shown;

[0027] Figure 2 The diagram illustrates a step in the maximum power point tracking method of an embodiment of the present invention, which involves determining the perturbation direction of the reference voltage based on the magnitude relationship between the output power of three operating points and adjusting the perturbation step size.

[0028] Figure 3 The diagram illustrates a step in the maximum power point tracking method according to an embodiment of the present invention: calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltages and output power of three operating points.

[0029] Figure 4 The diagram illustrates a flow chart of a maximum power point tracking method according to an embodiment of the present invention, following the step of outputting the voltage of the theoretical maximum power point as an updated reference voltage.

[0030] Figure 5 The diagram illustrates a step in the maximum power point tracking method of an embodiment of the present invention, which involves updating three operating points based on the magnitude between the voltage of the theoretical maximum power point and the voltage of the medium-voltage operating point.

[0031] Figure 6 A second schematic flowchart of a maximum power point tracking method according to an embodiment of the present invention is shown;

[0032] Figure 7 A block diagram of a maximum power point tracking system according to an embodiment of the present invention is shown. Detailed Implementation

[0033] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0034] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0035] Figure 1 One of the flowcharts of a maximum power point tracking method according to an embodiment of the present invention is shown, wherein the maximum power point tracking method includes:

[0036] Step 102: Collect the initial input voltage of the photovoltaic module, and determine the reference voltage and disturbance step size based on the initial input voltage;

[0037] Step 104: Using the reference voltage as the median, determine three operating points according to the disturbance step size, and collect the output power of the three operating points respectively. The three operating points are: low voltage operating point, medium voltage operating point and high voltage operating point.

[0038] Step 106: Determine the perturbation direction of the reference voltage based on the relationship between the output power of the three operating points, and adjust the perturbation step size;

[0039] Step 108: When the adjusted disturbance step size is less than or equal to the preset step size threshold, the voltage of the theoretical maximum power point is calculated by using a quadratic interpolation formula based on the voltage and output power of the three operating points.

[0040] Step 110: Use the voltage of the theoretical maximum power point as the updated reference voltage output.

[0041] The maximum power point tracking (MPPT) method provided by this invention mainly includes: first, acquiring the initial input voltage (open-circuit voltage) of the photovoltaic module; then, determining a reference voltage and a perturbation step size based on the initial input voltage. The reference voltage can be 80% of the initial input voltage, and the perturbation step size can be 5% of the initial input voltage. The reference voltage is the target control voltage of the photovoltaic converter and also the output control quantity of the MPPT algorithm. The perturbation step size refers to the voltage interval for each adjustment of the reference voltage, supporting dynamic amplification and reduction. After obtaining the reference voltage and perturbation step size, three operating points are determined based on the reference voltage as the median and the perturbation step size. The output power of each of the three operating points is then collected. These three operating points are the low-voltage operating point, the medium-voltage operating point, and the high-voltage operating point. In other words, the point corresponding to the reference voltage is designated as the medium-voltage operating point, the point corresponding to the sum of the reference voltage and the perturbation step size is designated as the high-voltage operating point, and the point corresponding to the difference between the reference voltage and the perturbation step size is designated as the low-voltage operating point. Subsequently, the output power of the photovoltaic module when its output voltage is the voltage of the medium-voltage operating point (i.e., the reference voltage) is collected as the output power of the medium-voltage operating point. The output power of the photovoltaic module when its output voltage is the voltage of the low-voltage operating point (i.e., the difference between the reference voltage and the perturbation step size) is collected as the output power of the low-voltage operating point. Finally, the output power of the photovoltaic module when its output voltage is the voltage of the high-voltage operating point (i.e., the sum of the reference voltage and the perturbation step size) is collected as the output power of the high-voltage operating point. Then, the output power at the three operating points is compared to determine the perturbation direction of the reference voltage. The perturbation step size is adjusted accordingly. The perturbation direction refers to the adjustment offset direction of the reference voltage, which is divided into a low-voltage direction and a high-voltage direction. The low-voltage direction involves decreasing the reference voltage according to the perturbation step size, while the high-voltage direction involves increasing the reference voltage according to the perturbation step size. After determining the perturbation direction, the reference voltage is adjusted accordingly. Based on the adjusted reference voltage and the adjusted perturbation step size, the three operating points and their output power are redefined. The reference voltage and perturbation step size are then readjusted based on the output power at the three operating points. This process is repeated until the adjusted perturbation step size is less than or equal to a preset step size threshold.

[0042] When the adjusted perturbation step size is less than or equal to the preset step size threshold, the theoretical maximum power point voltage is calculated using a quadratic interpolation formula based on the voltage and output power of the three operating points corresponding to the adjusted perturbation step size. This involves fitting the photovoltaic power unit (PU) parabolic curve using the voltage and output power of the three operating points, and directly solving for the vertex of the parabola through the slope at two points, thus obtaining the theoretical maximum power point voltage. Finally, the calculated theoretical maximum power point voltage is assigned as the updated reference voltage and output as the voltage control target of the photovoltaic converter. This scheme first collects the initial photovoltaic input voltage to generate a reference voltage and perturbation step size. It then uses power sampling at low, medium, and high voltage points to achieve a coarse search with a variable step size. Under a wide range of operating conditions, this can quickly narrow down the voltage range of the MPP (Maximum Power Point), significantly shortening the convergence time for long-distance optimization and avoiding large deviations between the operating voltage and the true maximum power point. When the perturbation step size is reduced to the threshold, the quadratic interpolation fine calculation mode is switched, allowing for accurate calculation of the theoretical maximum power point voltage without continuous repetitive perturbation, thus eliminating steady-state power fluctuation losses. Compared to traditional fixed small step size algorithms, this invention is adapted to high voltage wide voltage photovoltaic scenarios of 30V~450V, which not only ensures long-distance tracking speed, but also eliminates steady-state power oscillation, effectively reduces power generation energy loss, and stably maintains a high MPPT tracking efficiency of over 99.9%.

[0043] Figure 2 The diagram illustrates a step in a maximum power point tracking method according to an embodiment of the present invention: determining the perturbation direction of a reference voltage based on the magnitude relationship between the output power of three operating points, and adjusting the perturbation step size. The step of determining the perturbation direction of the reference voltage based on the magnitude relationship between the output power of the three operating points and adjusting the perturbation step size includes:

[0044] Step 202: If the output power at the medium-voltage operating point is at its maximum value, then reduce the disturbance step size according to the first preset rule;

[0045] Step 204: If the output power at the low-voltage operating point is at its maximum value, then the disturbance direction is determined to be the low-voltage direction. The reference voltage is disturbed in the low-voltage direction by a disturbance step size, and then the disturbance step size is amplified according to the second preset rule.

[0046] Step 206: If the output power of the high-voltage operating point is at its maximum value, then the disturbance direction is determined to be the high-voltage direction. The reference voltage is disturbed in the high-voltage direction by a disturbance step size, and then the disturbance step size is amplified according to the second preset rule.

[0047] In this embodiment, the step of determining the perturbation direction of the reference voltage based on the relationship between the output power of the three operating points and adjusting the perturbation step size includes: when the output power of the medium-voltage operating point is the maximum, it means that the current reference voltage is close to the true maximum power point. Therefore, the perturbation step size is reduced only by the first preset rule without deviating from the reference voltage. That is, when the output power of the medium-voltage operating point is the maximum, it is only necessary to reduce the perturbation range to continue tracking. When the output power of the low-voltage operating point is the maximum, it means that the MPP is located to the left of the current voltage, and the perturbation direction is the low-voltage direction. Therefore, the reference voltage is perturbed towards the low-voltage direction by one perturbation step size, that is, the reference voltage is subtracted by one perturbation step size to obtain a new reference voltage. Then, the perturbation step size is amplified by the second preset rule. That is, when the output power of the low-voltage operating point is the maximum, the voltage corresponding to the low-voltage operating point is used as the new reference voltage. Then, the perturbation step size is amplified, and finally, the three new operating points are re-determined based on the amplified perturbation step size and the new reference voltage, that is, the search range is expanded after the reference voltage is reduced. When the output power of the high-voltage operating point is at its maximum, it indicates that the MPP is located to the right of the current voltage, and the perturbation direction is towards the high voltage. Therefore, the reference voltage is perturbed towards the high voltage direction by one perturbation step, i.e., the reference voltage is increased by one perturbation step to obtain a new reference voltage. Then, the perturbation step is amplified by the second preset rule. In other words, when the output power of the high-voltage operating point is at its maximum, the voltage corresponding to the high-voltage operating point is used as the new reference voltage. Then, the perturbation step is amplified, and finally, three new operating points are re-determined based on the amplified perturbation step and the new reference voltage, i.e., the search range is expanded by increasing the reference voltage. Among them, the first preset rule is used to narrow the search interval when approaching the optimal interval, and the second preset rule is used to expand the search range when moving away from the MPP. Combining the three power extreme values, the interval where the MPP is located is accurately determined, and the voltage offset and step scaling operations are completed simultaneously. This invention addresses the shortcomings of traditional single-point power judgment, such as misjudgment of the optimization direction and slow convergence at long distances. Under high-voltage, wide-range photovoltaic operating conditions ranging from 30V to 450V, it automatically increases the step size to rapidly compress the search interval when far from the maximum power point, significantly shortening the optimization convergence time and reducing power generation losses caused by voltage deviations at long distances. Simultaneously, it continuously reduces the step size as it approaches the maximum power point (MPP), gradually narrowing the disturbance range and providing accurate sampling data for subsequent interpolation calculations, balancing dynamic tracking speed with steady-state sampling accuracy.

[0048] In some embodiments, optionally, the first preset rule is to multiply the perturbation step size by a preset coefficient, and the second preset rule is to divide the perturbation step size by a preset coefficient, wherein the preset coefficient is less than 1.

[0049] In this embodiment, the first preset rule for reducing the step size is the perturbation step size multiplied by a preset coefficient, and the second preset rule for increasing the step size is the perturbation step size divided by the same preset coefficient, where the preset coefficient is always less than 1, and can be 0.8. Using the same coefficient to achieve symmetrical scaling logic ensures a balanced and uniform change in the step size reduction and expansion. This invention solves the problem of unidirectional drift and continuous oscillation of the three-point sampling window after multiple iterations when different ratios are used for expansion and contraction in existing variable step size algorithms. The symmetrical scaling mechanism prevents the voltage search interval from continuously deviating from the optimal region, improving the operational stability during the coarse tracking stage in a high-voltage wide-range voltage range. Simultaneously, setting the preset coefficient to 0.8 balances convergence speed and step size smoothness, preventing voltage surges in the converter caused by sudden increases or decreases in step size, and reducing the probability of hardware failure.

[0050] Figure 3 The diagram illustrates a step in a maximum power point tracking method according to an embodiment of the present invention: calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltages of three operating points and the output power. The step of calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltages of the three operating points and the output power includes:

[0051] Step 302: Construct a first curve based on the voltage at the low-voltage operating point, the output power at the low-voltage operating point, the voltage at the medium-voltage operating point, and the output power at the medium-voltage operating point, and calculate the first slope of the first curve;

[0052] Step 304: Construct a second curve based on the voltage of the high-voltage operating point, the output power of the high-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and calculate the second slope of the second curve;

[0053] Step 306: Calculate the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage of the low-voltage operating point, the voltage of the medium-voltage operating point, the voltage of the high-voltage operating point, the first slope, and the second slope.

[0054] In this embodiment, the step of calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage and output power of three operating points includes: First, constructing a first curve, i.e., the first PU curve, based on the voltage of the low-voltage operating point, the output power of the low-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and calculating the first slope of the first PU curve. Then, constructing a second curve, i.e., the second PU curve, based on the voltage of the high-voltage operating point, the output power of the high-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and calculating the second slope of the second PU curve. Finally, substituting the voltage of the low-voltage operating point, the voltage of the medium-voltage operating point, the voltage of the high-voltage operating point, the first slope, and the second slope into the quadratic interpolation formula, fitting a quadratic parabola of photovoltaic power, and directly calculating the vertex of the parabola, i.e., the voltage of the theoretical maximum power point. The quadratic interpolation formula is Vmpp = {(U1+U2)×K23-(U2+U3)×K12}÷[2×(K23-K12)], where Vmpp is the voltage at the theoretical maximum power point, U1 is the voltage at the low-voltage operating point, U2 is the voltage at the medium-voltage operating point (i.e., the current reference voltage), U3 is the voltage at the high-voltage operating point, K12 is the slope of the PU curve between the low-voltage and medium-voltage operating points, where K12 = (P2-P1)÷(U2-U1), P1 is the output power at the low-voltage operating point, P2 is the output power at the medium-voltage operating point, and K23 is the slope of the PU curve between the high-voltage and medium-voltage operating points, where K23 = (P3-P2)÷(U3-U2), P3 is the output power at the high-voltage operating point. This invention differs from the traditional method of approximating through repeated perturbations. It can accurately locate the MPP through mathematical calculations using only a set of three-point sampling data, completely eliminating the power loss caused by periodic voltage disturbances under steady state. It is suitable for 30V~450V high-voltage photovoltaic scenarios and significantly reduces the energy loss caused by continuous high-voltage disturbances.

[0055] Figure 4 The diagram illustrates a flow chart of a maximum power point tracking method according to an embodiment of the present invention after the step of outputting the voltage of the theoretical maximum power point as an updated reference voltage. Following the step of outputting the voltage of the theoretical maximum power point as an updated reference voltage, the maximum power point tracking method further includes:

[0056] Step 402: Update the three operating points based on the difference between the voltage at the theoretical maximum power point and the voltage at the medium-voltage operating point;

[0057] Step 404: Recalculate the voltage of the theoretical maximum power point based on the updated voltages of the three operating points and the output power, and re-output the updated voltage of the theoretical maximum power point as the updated reference voltage.

[0058] In this embodiment, after the step of using the voltage of the theoretical maximum power point (MPP) as the updated reference voltage output, the MPP tracking method further includes: after obtaining the voltage of the theoretical MPP through a single interpolation, comparing the obtained voltage of the theoretical MPP with the voltage of the medium-voltage operating point, and updating the three operating points according to the magnitude relationship. Subsequently, based on the updated voltages and output power of the three operating points, slope calculation and secondary interpolation are performed again to obtain the voltage of the new theoretical MPP, and the updated reference voltage is output cyclically, thereby achieving continuous iterative tracking. This invention solves the defects of single interpolation, which only locates the optimal voltage once, and the sampling window deviates from the MPP and the tracking accuracy decreases after the illumination slowly drifts. The three-point window continuously keeps close to the real-time maximum power point, and there will be no power deviation during long-term steady-state operation. In this invention, the voltage change is gradual through smooth iterative window updates, reducing the inductor current fluctuation of the photovoltaic converter, avoiding current overshoot triggering hardware protection, and improving the overall reliability of the machine.

[0059] Figure 5 The diagram illustrates a step in a maximum power point tracking method according to an embodiment of the present invention: updating three operating points based on the magnitude between the voltage of the theoretical maximum power point and the voltage of the intermediate voltage operating point. This step includes:

[0060] Step 502: If the voltage of the theoretical maximum power point is less than the voltage of the medium voltage operating point, then the original medium voltage operating point is taken as the new high voltage operating point, and the theoretical maximum power point is taken as the new medium voltage operating point.

[0061] Step 504: If the voltage of the theoretical maximum power point is greater than the voltage of the medium voltage operating point, then the original medium voltage operating point is taken as the new low voltage operating point, and the theoretical maximum power point is taken as the new medium voltage operating point.

[0062] In this embodiment, the step of updating the three operating points based on the difference between the voltage of the theoretical maximum power point and the voltage of the intermediate voltage operating point includes: if the voltage of the theoretical maximum power point is less than the voltage of the intermediate voltage operating point, then the original intermediate voltage operating point is used as the new high voltage operating point, and the theoretical maximum power point is used as the new intermediate voltage operating point. That is, when Vmpp is less than the voltage of the intermediate voltage operating point, the window slides to the lower voltage, the voltage and output power of the original intermediate voltage operating point are assigned to the voltage and output power of the new high voltage operating point, the voltage and output power of the theoretical maximum power point are used as the voltage and output power of the new intermediate voltage operating point, and a new low voltage operating point is determined based on the new intermediate voltage operating point and the disturbance step size. If the voltage of the theoretical maximum power point is greater than the voltage of the medium-voltage operating point, the original medium-voltage operating point is used as the new low-voltage operating point, and the theoretical maximum power point is used as the new medium-voltage operating point. In other words, when Vmpp is greater than the original medium-voltage operating point, the window slides towards the high-voltage side. The voltage and output power of the original medium-voltage operating point are assigned to the voltage and output power of the new low-voltage operating point, and the voltage and output power of the theoretical maximum power point are used as the voltage and output power of the new medium-voltage operating point. Furthermore, the new high-voltage operating point is determined based on the new medium-voltage operating point and the disturbance step size. This invention unifies the sliding window update logic, simplifies decision branches, and reduces the computational burden on the program. Simultaneously, the window only shifts slightly in one direction, eliminating large voltage jumps, optimizing voltage output smoothness, reducing PWM duty cycle abrupt changes, reducing switching impact on power devices, and extending the lifespan of photovoltaic converters and photovoltaic modules. Furthermore, by using a three-point sampling interval that always revolves around the real-time optimal voltage, long-term high accuracy in interpolation calculations is ensured.

[0063] In some embodiments, optionally, after the step of calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage and output power of the three operating points, the maximum power point tracking method further includes: if the output power of the theoretical maximum power point is less than the output power of any one of the three operating points, then using the voltage of the theoretical maximum power point as the median, the three operating points are re-determined according to the current perturbation step size.

[0064] In this embodiment, after calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage and output power of the three operating points, the maximum power point tracking method further includes: if the output power of the theoretical maximum power point is less than the output power of any one of the three operating points, then the voltage of the theoretical maximum power point is used as the median, and the three operating points are re-determined according to the current perturbation step size. In other words, after calculating Vmpp through secondary interpolation, the actual output power corresponding to Vmpp is verified. If the actual output power is lower than any set of three-point sampling power, it is determined that there is a sudden change in illumination and the current three-point fitting curve has failed. The interpolation fine calculation mode is automatically exited, and Vmpp is used as the new median. The three operating points are re-divided using the current perturbation step size, and the variable step size coarse perturbation tracking process is resumed. That is, the reference voltage is used as the median, and the three operating points are re-determined according to the current perturbation step size. The output power of the three operating points is collected respectively. Then, based on the relationship between the output power of the three operating points, the perturbation direction of the reference voltage is determined, and the perturbation step size is adjusted. Then, based on the adjusted reference voltage and the adjusted perturbation step size, the three operating points and the output power of the three operating points are re-determined, and the reference voltage and perturbation step size are readjusted based on the output power of the three operating points. This process is repeated until the adjusted perturbation step size is less than or equal to the preset step size threshold. This invention solves the defects of interpolation fitting curve distortion, algorithm locking of local suboptimal advantages, and tracking failure when cloud cover and drastic changes in irradiance. It realizes automatic mode switching of the algorithm under dynamic lighting conditions, sensitive tracking response when the lighting changes suddenly, and takes into account the dual advantages of high accuracy of steady-state interpolation and fast convergence of dynamic coarse search.

[0065] Figure 6 The second schematic flowchart of a maximum power point tracking method according to an embodiment of the present invention is shown, wherein the maximum power point tracking method includes:

[0066] Step 602: Open circuit voltage Vopen = current voltage Vin;

[0067] Step 604: Reference voltage Vref = Vopen × 0.8;

[0068] Step 606: Step size Vstep = Vopen × 0.02;

[0069] Step 608: Determine if abs(Vref-Vopen) < 5; if the result is yes, proceed to step 610; if the result is no, proceed to step 612.

[0070] Step 610: Vopen = Vopen + 10;

[0071] Step 612: Voltage Vset = Vref, U2 = Vset;

[0072] Step 614: Median power Pow2 = Current power Pin;

[0073] Step 616: Working voltage Vset = Vref + Vstep, U3 = Vset;

[0074] Step 618: High-value power Pow3 = Current power Pin;

[0075] Step 620: Working voltage Vset = Vref - Vstep, U1 = Vset;

[0076] Step 622: Low power Pow1 = Current power Pin;

[0077] Step 624: Determine whether Pow2 > Pow3 && Pow1 < Pow2. If the result is no, proceed to step 626. If the result is yes, proceed to step 634.

[0078] Step 626: Determine whether Pow1 > Pow2 && Pow2 > Pow3. If the result is no, proceed to step 628. If the result is yes, proceed to step 630.

[0079] Step 628: Determine whether Pow1 < Pow2 && Pow2 < Pow3. If the result is yes, then proceed to step 632.

[0080] Step 630: Vref = Vref - Vstep, Vstep = Vstep ÷ 0.8;

[0081] Step 632: Vref = Vref + Vstep, Vstep = Vstep ÷ 0.8;

[0082] Step 634: Vstep = Vstep × 0.8;

[0083] Step 636: Determine if Vstep < 3. If the result is yes, proceed to step 638; if the result is no, proceed to step 614.

[0084] Step 638: K12 = (Pow2 - Pow1) ÷ (U2 - U1), K23 = (Pow3 - Pow2) ÷ (U3 - U2);

[0085] Step 640: Vmpp = {(U1+U2)×K23-(U2+U3)×K12}÷[2×(K23-K12)];

[0086] Step 642: Determine if Vmpp < U2. If the result is no, proceed to step 644. If the result is yes, proceed to step 646.

[0087] Step 644: Determine if Vmpp > U2. If the result is yes, proceed to step 648; if the result is no, proceed to step 650.

[0088] Step 646: U3=U2, Pow3=Pow2, U2=Vmpp;

[0089] Step 648: U1=U2, Pow1=Pow2, U2=Vmpp;

[0090] Step 650: Vset=Vmpp, Vref=Vmpp;

[0091] Step 652: Pow2 = Pin;

[0092] Step 654: Determine whether Pow2 > Pow1 && Pow2 < Pow3. If the result is yes, proceed to step 638; if the result is no, proceed to step 614.

[0093] In this embodiment, a photovoltaic module is connected, and the current input voltage Vin of the photovoltaic module is read as the open-circuit voltage Vopen. The initial reference voltage Vref is equal to 80% of the open-circuit voltage Vopen, and the perturbation step size Vstep is equal to 2% of the open-circuit voltage Vopen. Subsequently, it is determined whether the absolute value of the difference between the reference voltage Vref and the open-circuit voltage Vopen is less than 5. If the condition is met, the open-circuit voltage Vopen is increased by 10 to update the open-circuit voltage parameter in a timely manner when the light intensity increases; if not, the process continues. Using the reference voltage Vref as the median point, the voltage and output power of three operating points are collected sequentially: Vref is assigned to U2 to collect the median power Pow2; Vref+Vstep is assigned to U3 to collect the high-value power Pow3; and Vref-Vstep is assigned to U1 to collect the low-value power Pow1, completing the sampling of voltage and power at the low, medium, and high voltage points.

[0094] Then, the variable step size perturbation logic is executed by comparing the power values ​​of the three points. When the median power Pow2 is the maximum of the three, the perturbation step size Vstep is multiplied by 0.8 to narrow the perturbation search range without changing the reference voltage. If the low power Pow1 is the maximum, the reference voltage Vref is subtracted by one perturbation step size Vstep, and the perturbation step size Vstep is divided by 0.8 for amplification. If the high power Pow3 is the maximum, the reference voltage Vref is added up by one perturbation step size Vstep, and the perturbation step size Vstep is divided by 0.8 for amplification.

[0095] Then, it is determined whether the perturbation step size Vstep is less than 3V. If the step size is greater than or equal to 3V, the process returns to the three-point sampling step and continues with variable step size coarse tracking. When the perturbation step size Vstep is less than 3V, the process enters the secondary interpolation fine optimization stage: the slopes K12 and K23 of the two PU curves are calculated using the three-point voltage and power, and then substituted into the secondary interpolation formula to calculate the theoretical maximum power point voltage Vmpp. Subsequently, Vmpp is compared with the median voltage U2. If Vmpp is less than U2, the sliding three-point window is moved downwards, setting U3=U2 and Pow3=Pow2, and U2 is updated to Vmpp. If Vmpp is greater than U2, the sliding three-point window is moved upwards, setting U1=U2 and Pow1=Pow2, and U2 is updated to Vmpp.

[0096] Vset and Vref are assigned the value Vmpp, and the current power Pin is re-acquired and assigned to Pow2. Then, it is determined whether the current median power Pow2 is greater than both Pow1 and Pow3. If the condition is met, the interpolation result is valid, and the sliding window iterative interpolation mode is maintained, with cyclic calculations and continuous output of the reference voltage to ensure the converter operates stably at its maximum power point. If the condition is not met, a sudden change in illumination conditions is detected, the interpolation fine calculation is exited, the three-point sampling process is returned to, and variable-step perturbation coarse tracking is restarted. Throughout the process, boundary constraints are added to the perturbation step size Vstep, with the upper limit not exceeding 20% ​​of the open-circuit voltage Vopen and the lower limit not lower than 0.5V.

[0097] Figure 7 A structural block diagram of a maximum power point tracking system according to an embodiment of the present invention is shown, wherein the maximum power point tracking system 70 includes:

[0098] The first processing module 702 is used to collect the initial input voltage of the photovoltaic module and determine the reference voltage and disturbance step size based on the initial input voltage.

[0099] The second processing module 704 is used to determine three operating points based on the reference voltage as the median and the disturbance step size, and to collect the output power of the three operating points respectively. The three operating points are: low voltage operating point, medium voltage operating point and high voltage operating point.

[0100] The third processing module 706 is used to determine the disturbance direction of the reference voltage based on the magnitude relationship between the output power of the three operating points, and to adjust the disturbance step size.

[0101] The fourth processing module 708 is used to calculate the voltage of the theoretical maximum power point by using a quadratic interpolation formula based on the voltage and output power of the three operating points when the adjusted disturbance step size is less than or equal to the preset step size threshold.

[0102] The fifth processing module 710 is used to output the voltage of the theoretical maximum power point as the updated reference voltage.

[0103] The maximum power point tracking (MPPT) system 70 provided by this invention mainly includes: a first processing module 702, a second processing module 704, a third processing module 706, a fourth processing module 708, and a fifth processing module 710. The first processing module 702 first acquires the initial input voltage (open-circuit voltage) of the photovoltaic module. Then, based on the initial input voltage, it determines a reference voltage and a perturbation step size. The reference voltage can be 80% of the initial input voltage, and the perturbation step size can be 5% of the initial input voltage. The reference voltage is the target control voltage of the photovoltaic converter and also the output control quantity of the MPPT algorithm. The perturbation step size refers to the voltage interval for each adjustment of the reference voltage, supporting dynamic amplification and reduction. After obtaining the reference voltage and the perturbation step size, the second processing module 704 uses the reference voltage as the median and determines three operating points according to the perturbation step size. It then collects the output power of each of the three operating points: a low-voltage operating point, a medium-voltage operating point, and a high-voltage operating point. Specifically, the point corresponding to the reference voltage is designated as the medium-voltage operating point, the point corresponding to the sum of the reference voltage and the perturbation step size is designated as the high-voltage operating point, and the point corresponding to the difference between the reference voltage and the perturbation step size is designated as the low-voltage operating point. Subsequently, the output power of the photovoltaic module when its output voltage is the voltage of the medium-voltage operating point (i.e., the reference voltage) is collected as the output power of the medium-voltage operating point. Similarly, the output power of the photovoltaic module when its output voltage is the voltage of the low-voltage operating point (i.e., the difference between the reference voltage and the perturbation step size) is collected as the output power of the low-voltage operating point. Finally, the output power of the photovoltaic module when its output voltage is the voltage of the high-voltage operating point (i.e., the sum of the reference voltage and the perturbation step size) is collected as the output power of the high-voltage operating point. Subsequently, the third processing module 706 compares the magnitude relationship between the output power of the three operating points, determines the disturbance direction of the reference voltage based on the magnitude relationship, and synchronously adjusts the size of the disturbance step size. The disturbance direction refers to the adjustment offset direction of the reference voltage, which is divided into a low-voltage direction and a high-voltage direction. The low-voltage direction refers to decreasing the reference voltage according to the disturbance step size, and the high-voltage direction refers to increasing the reference voltage according to the disturbance step size. After determining the disturbance direction, the reference voltage is adjusted according to the disturbance direction, and the three operating points and their output power are re-determined based on the adjusted reference voltage and the adjusted disturbance step size. The reference voltage and disturbance step size are then readjusted based on the output power of the three operating points. This process is repeated until the adjusted disturbance step size is less than or equal to a preset step size threshold.

[0104] When the adjusted perturbation step size is less than or equal to the preset step size threshold, the fourth processing module 708 uses a quadratic interpolation formula to calculate the theoretical maximum power point voltage based on the voltage and output power of the three operating points corresponding to the adjusted perturbation step size. Specifically, it fits the photovoltaic power unit (PU) parabolic curve using the voltage and output power of the three operating points, and directly solves for the vertex of the parabola through the slope at two points, thus obtaining the theoretical maximum power point voltage. Finally, the fifth processing module 710 assigns the calculated theoretical maximum power point voltage as the updated reference voltage and outputs it as the voltage control target of the photovoltaic converter. This scheme first collects the initial input voltage of the photovoltaic system to generate a reference voltage and perturbation step size. It achieves a coarse search with variable step size by sampling and comparing power at low, medium, and high voltage points. Under a wide range of operating conditions, it can quickly narrow down the voltage range where the MPP (Maximum Power Point) is located, significantly shortening the convergence time for long-distance optimization and avoiding large deviations between the operating voltage and the true maximum power point. When the perturbation step size is reduced to the threshold, it switches to a quadratic interpolation fine calculation mode, accurately solving for the theoretical maximum power point voltage without continuous repetitive perturbation, eliminating steady-state power fluctuation losses. Compared to traditional fixed small step size algorithms, this invention is adapted to high voltage wide voltage photovoltaic scenarios of 30V~450V, which not only ensures long-distance tracking speed, but also eliminates steady-state power oscillation, effectively reduces power generation energy loss, and stably maintains a high MPPT tracking efficiency of over 99.9%.

[0105] In some embodiments, optionally, the third processing module 706 is specifically configured to: if the output power of the medium-voltage operating point is at its maximum value, reduce the disturbance step size according to a first preset rule; if the output power of the low-voltage operating point is at its maximum value, determine that the disturbance direction is the low-voltage direction, disturb the reference voltage in the low-voltage direction by one disturbance step size, and then amplify the disturbance step size according to a second preset rule; if the output power of the high-voltage operating point is at its maximum value, determine that the disturbance direction is the high-voltage direction, disturb the reference voltage in the high-voltage direction by one disturbance step size, and then amplify the disturbance step size according to the second preset rule.

[0106] In this embodiment, the third processing module 706 is specifically used when the output power of the medium-voltage operating point is at its maximum, indicating that the current reference voltage is close to the true maximum power point. Therefore, it only reduces the perturbation step size according to the first preset rule without deviating from the reference voltage. In other words, when the output power of the medium-voltage operating point is at its maximum, it only needs to reduce the perturbation range to continue tracking. When the output power of the low-voltage operating point is at its maximum, it means that the MPP is located to the left of the current voltage, and the perturbation direction is the low-voltage direction. Therefore, it perturbs the reference voltage by one perturbation step size in the low-voltage direction, that is, it subtracts one perturbation step size from the reference voltage to obtain a new reference voltage. Then, it amplifies the perturbation step size according to the second preset rule. That is, when the output power of the low-voltage operating point is at its maximum, the voltage corresponding to the low-voltage operating point is used as the new reference voltage. Then, the perturbation step size is amplified, and finally, three new operating points are re-determined based on the amplified perturbation step size and the new reference voltage, that is, the search range is expanded after the reference voltage is reduced. When the output power of the high-voltage operating point is at its maximum, it indicates that the MPP is located to the right of the current voltage, and the perturbation direction is towards the high voltage. Therefore, the reference voltage is perturbed towards the high voltage direction by one perturbation step, i.e., the reference voltage is increased by one perturbation step to obtain a new reference voltage. Then, the perturbation step is amplified by the second preset rule. In other words, when the output power of the high-voltage operating point is at its maximum, the voltage corresponding to the high-voltage operating point is used as the new reference voltage. Then, the perturbation step is amplified, and finally, three new operating points are re-determined based on the amplified perturbation step and the new reference voltage, i.e., the search range is expanded by increasing the reference voltage. Among them, the first preset rule is used to narrow the search interval when approaching the optimal interval, and the second preset rule is used to expand the search range when moving away from the MPP. Combining the three power extreme values, the interval where the MPP is located is accurately determined, and the voltage offset and step scaling operations are completed simultaneously. This invention solves the shortcomings of traditional single-point power judgment, which is prone to misjudgment of the optimization direction and slow convergence of long-distance search. Under the high voltage and wide range of photovoltaic conditions of 30V~450V, it automatically increases the step size and quickly compresses the search interval when far away from the maximum power point, which greatly shortens the optimization convergence time and reduces the power generation loss caused by long-distance voltage deviation.

[0107] In some embodiments, optionally, the first preset rule is to multiply the perturbation step size by a preset coefficient, and the second preset rule is to divide the perturbation step size by a preset coefficient, wherein the preset coefficient is less than 1.

[0108] In this embodiment, the first preset rule for reducing the step size is the perturbation step size multiplied by a preset coefficient, and the second preset rule for increasing the step size is the perturbation step size divided by the same preset coefficient, where the preset coefficient is always less than 1, and can be 0.8. Using the same coefficient to achieve symmetrical scaling logic ensures that the changes in step size reduction and expansion are balanced and uniform. This invention solves the problem of unidirectional drift and continuous oscillation of the three-point sampling window after multiple iterations due to different scaling ratios used in existing variable step size algorithms. The symmetrical scaling mechanism prevents the voltage search interval from continuously deviating from the optimal region, improving the operational stability during the coarse tracking stage of a high-voltage wide-range voltage range.

[0109] In some embodiments, optionally, the fourth processing module 708 is specifically configured to construct a first curve based on the voltage of the low-voltage operating point, the output power of the low-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and calculate a first slope of the first curve; construct a second curve based on the voltage of the high-voltage operating point, the output power of the high-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and calculate a second slope of the second curve; and calculate the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage of the low-voltage operating point, the voltage of the medium-voltage operating point, the voltage of the high-voltage operating point, the first slope, and the second slope.

[0110] In this embodiment, the fourth processing module 708 is specifically used to first construct a first curve, i.e., the first PU curve, based on the voltage of the low-voltage operating point, the output power of the low-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and calculate the first slope of the first PU curve. Then, based on the voltage of the high-voltage operating point, the output power of the high-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, a second curve, i.e., the second PU curve, is constructed, and the second slope of the second PU curve is calculated. Finally, the voltage of the low-voltage operating point, the voltage of the medium-voltage operating point, the voltage of the high-voltage operating point, the first slope, and the second slope are substituted into a quadratic interpolation formula to fit a quadratic parabola of photovoltaic power and directly calculate the vertex of the parabola, i.e., the voltage of the theoretical maximum power point. This invention differs from the traditional method of repeated perturbation approximation; it can accurately locate the MPP through mathematical calculations using only a set of three-point sampling data, completely eliminating power loss caused by periodic voltage perturbations under steady-state conditions.

[0111] In some embodiments, the maximum power point tracking system 70 may optionally include: a sixth processing module for updating the three operating points based on the magnitude between the voltage of the theoretical maximum power point and the voltage of the intermediate voltage operating point; and a seventh processing module for recalculating the voltage of the theoretical maximum power point based on the updated voltages of the three operating points and the output power, and re-outputting the updated voltage of the theoretical maximum power point as the updated reference voltage.

[0112] In this embodiment, the maximum power point tracking system 70 further includes a sixth processing module and a seventh processing module. After obtaining the voltage of the theoretical maximum power point through a single interpolation, the sixth processing module compares the obtained voltage of the theoretical maximum power point with the voltage of the medium-voltage operating point, and updates the three operating points according to the magnitude relationship. Subsequently, the seventh processing module performs slope calculation and secondary interpolation again based on the updated voltages and output power of the three operating points to obtain the voltage of the new theoretical maximum power point, and cyclically outputs the updated reference voltage, thereby achieving continuous iterative tracking. This invention solves the shortcomings of single interpolation, which only locates the optimal voltage once, and whose sampling window deviates from the MPP and tracking accuracy decreases after slow light drift. The three-point window continuously keeps close to the real-time maximum power point, and no power deviation occurs during long-term steady-state operation.

[0113] In some embodiments, optionally, the sixth processing module is specifically used to, if the voltage of the theoretical maximum power point is less than the voltage of the medium voltage operating point, then take the original medium voltage operating point as the new high voltage operating point and the theoretical maximum power point as the new medium voltage operating point; if the voltage of the theoretical maximum power point is greater than the voltage of the medium voltage operating point, then take the original medium voltage operating point as the new low voltage operating point and the theoretical maximum power point as the new medium voltage operating point.

[0114] In this embodiment, the sixth processing module is specifically used to, if the voltage of the theoretical maximum power point is less than the voltage of the medium-voltage operating point, take the original medium-voltage operating point as the new high-voltage operating point and the theoretical maximum power point as the new medium-voltage operating point. That is, when Vmpp is less than the voltage of the medium-voltage operating point, the window slides to the low voltage, assigns the voltage and output power of the original medium-voltage operating point to the voltage and output power of the new high-voltage operating point, takes the voltage and output power of the theoretical maximum power point as the voltage and output power of the new medium-voltage operating point, and determines the new low-voltage operating point based on the new medium-voltage operating point and the disturbance step size. If the voltage of the theoretical maximum power point is greater than the voltage of the medium-voltage operating point, then the original medium-voltage operating point is used as the new low-voltage operating point, and the theoretical maximum power point is used as the new medium-voltage operating point. In other words, when Vmpp is greater than the original medium-voltage operating point, the window slides towards the high-voltage side. The voltage and output power of the original medium-voltage operating point are assigned to the voltage and output power of the new low-voltage operating point, and the voltage and output power of the theoretical maximum power point are used as the voltage and output power of the new medium-voltage operating point. Furthermore, the new high-voltage operating point is determined based on the new medium-voltage operating point and the disturbance step size. This invention unifies the sliding window update logic, simplifies decision branches, and reduces the computational burden on the program.

[0115] In some embodiments, the maximum power point tracking system 70 may optionally further include an eighth processing module, configured to, if the output power of the theoretical maximum power point is less than any one of the output powers of the three operating points, use the voltage of the theoretical maximum power point as the median and redetermine the three operating points according to the current perturbation step size.

[0116] In this embodiment, the maximum power point tracking system 70 further includes an eighth processing module. If the output power of the theoretical maximum power point is less than the output power of any one of the three operating points, the eighth processing module uses the voltage of the theoretical maximum power point as the median and redetermines the three operating points according to the current perturbation step size. In other words, after calculating Vmpp through secondary interpolation, the actual output power corresponding to Vmpp is verified. If the actual output power is lower than any set of three-point sampling power, it is determined that there is a sudden change in illumination and the current three-point fitting curve has failed. The interpolation fine calculation mode is automatically exited, and Vmpp is used as the new median. The three operating points are re-divided using the current perturbation step size, and the variable step size coarse perturbation tracking process is resumed. That is, the reference voltage is used as the median, and the three operating points are re-determined according to the current perturbation step size. The output power of the three operating points is collected respectively. Then, based on the relationship between the output power of the three operating points, the perturbation direction of the reference voltage is determined, and the perturbation step size is adjusted. Then, based on the adjusted reference voltage and the adjusted perturbation step size, the three operating points and the output power of the three operating points are re-determined, and the reference voltage and perturbation step size are readjusted based on the output power of the three operating points. This process is repeated until the adjusted perturbation step size is less than or equal to the preset step size threshold. This invention solves the defects of interpolation fitting curve distortion, algorithm locking of local suboptimal advantages, and tracking failure when cloud cover and drastic changes in irradiance. It realizes automatic mode switching of the algorithm under dynamic lighting conditions, sensitive tracking response when the lighting changes suddenly, and takes into account the dual advantages of high accuracy of steady-state interpolation and fast convergence of dynamic coarse search.

[0117] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance, unless otherwise expressly specified and limited. The terms "connection," "installation," and "fixing," etc., should be interpreted broadly. For example, "connection" can mean a fixed connection, a detachable connection, or an integral connection; it can mean a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0118] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to specific features, structures, materials, or characteristics described in connection with an embodiment or example that are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0119] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A maximum power point tracking method, characterized in that, include: The initial input voltage of the photovoltaic module is collected, and the reference voltage and disturbance step size are determined based on the initial input voltage; Using the reference voltage as the median, three operating points are determined according to the disturbance step size, and the output power of the three operating points is collected respectively. The three operating points are: low voltage operating point, medium voltage operating point and high voltage operating point. Based on the relationship between the output power of the three operating points, the perturbation direction of the reference voltage is determined, and the perturbation step size is adjusted. When the adjusted disturbance step size is less than or equal to the preset step size threshold, the voltage of the theoretical maximum power point is calculated by a quadratic interpolation formula based on the voltage and output power of the three operating points. The voltage at the theoretical maximum power point is used as the updated reference voltage output.

2. The maximum power point tracking method according to claim 1, characterized in that, The step of determining the perturbation direction of the reference voltage based on the magnitude relationship between the output power of the three operating points and adjusting the perturbation step size includes: If the output power of the medium-voltage operating point is at its maximum value, then the disturbance step size is reduced according to the first preset rule; If the output power of the low-voltage operating point is at its maximum value, then the disturbance direction is determined to be the low-voltage direction, and the reference voltage is disturbed in the low-voltage direction by one disturbance step size, and then the disturbance step size is amplified according to the second preset rule; If the output power of the high-voltage operating point is at its maximum value, then the disturbance direction is determined to be the high-voltage direction, and the reference voltage is disturbed in the high-voltage direction by the disturbance step size, and then the disturbance step size is amplified according to the second preset rule.

3. The maximum power point tracking method according to claim 2, characterized in that, The first preset rule is to multiply the perturbation step size by a preset coefficient, and the second preset rule is to divide the perturbation step size by the preset coefficient, wherein the preset coefficient is less than 1.

4. The maximum power point tracking method according to claim 1, characterized in that, The step of calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage and output power of the three operating points includes: A first curve is constructed based on the voltage of the low-voltage operating point, the output power of the low-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and the first slope of the first curve is calculated. A second curve is constructed based on the voltage of the high-voltage operating point, the output power of the high-voltage operating point, the voltage of the medium-voltage operating point, and the output power of the medium-voltage operating point, and the second slope of the second curve is calculated. The voltage of the theoretical maximum power point is calculated using the quadratic interpolation formula based on the voltage of the low-voltage operating point, the voltage of the medium-voltage operating point, the voltage of the high-voltage operating point, the first slope, and the second slope.

5. The maximum power point tracking method according to claim 1, characterized in that, After the step of using the voltage of the theoretical maximum power point as the updated reference voltage output, the maximum power point tracking method further includes: Update the three operating points based on the magnitude of the difference between the voltage of the theoretical maximum power point and the voltage of the medium-voltage operating point; The voltage of the theoretical maximum power point is recalculated based on the updated voltages and output power of the three operating points, and the updated voltage of the theoretical maximum power point is used as the updated reference voltage output.

6. The maximum power point tracking method according to claim 5, characterized in that, The step of updating the three operating points based on the relationship between the voltage of the theoretical maximum power point and the voltage of the medium-voltage operating point includes: If the voltage of the theoretical maximum power point is less than the voltage of the medium voltage operating point, then the original medium voltage operating point is taken as the new high voltage operating point, and the theoretical maximum power point is taken as the new medium voltage operating point. If the voltage of the theoretical maximum power point is greater than the voltage of the medium voltage operating point, then the original medium voltage operating point is taken as the new low voltage operating point, and the theoretical maximum power point is taken as the new medium voltage operating point.

7. The maximum power point tracking method according to claim 1, characterized in that, After the step of calculating the voltage of the theoretical maximum power point using a quadratic interpolation formula based on the voltage and output power of the three operating points, the maximum power point tracking method further includes: If the output power of the theoretical maximum power point is less than the output power of any one of the three operating points, then the voltage of the theoretical maximum power point is used as the median, and the three operating points are re-determined according to the current disturbance step size.

8. A maximum power point tracking system, characterized in that, include: The first processing module is used to acquire the initial input voltage of the photovoltaic module and determine the reference voltage and the disturbance step size based on the initial input voltage. The second processing module is used to determine three operating points based on the reference voltage as the median and the disturbance step size, and to collect the output power of the three operating points respectively. The three operating points are: low voltage operating point, medium voltage operating point and high voltage operating point. The third processing module is used to determine the disturbance direction of the reference voltage based on the magnitude relationship between the output power of the three operating points, and to adjust the disturbance step size. The fourth processing module is used to calculate the voltage of the theoretical maximum power point by using a quadratic interpolation formula based on the voltage and output power of the three operating points when the adjusted disturbance step size is less than or equal to a preset step size threshold. The fifth processing module is used to output the voltage of the theoretical maximum power point as the updated reference voltage.

9. An inverter, characterized in that, include: The maximum power point tracking system as described in claim 8.

10. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the maximum power point tracking method as described in any one of claims 1 to 7.

Images