Maximum power point tracking method and equipment for photovoltaic array

Abstract

The invention relates to a maximum power point tracking method and device for a photovoltaic array, and the method comprises the steps: S1, starting the photovoltaic array until the current output voltage of the photovoltaic array is located in a first range of a maximum power point; s2, the current power of the photovoltaic array is obtained, disturbance voltage is applied, and the updated power of the photovoltaic array is obtained; s3, a power-voltage slope is obtained according to the current power and the updated power, and whether the slope is smaller than a critical threshold value or not is judged; if not, calculating and updating the disturbance voltage according to the current disturbance voltage and the slope, and returning to the step S2; if yes, determining a second range of the maximum power point according to the updated power and the current disturbance voltage, randomly selecting a plurality of different points in the second range, and fitting to obtain the maximum power point; the second range is smaller than the first range. The problems that the maximum output power of the photovoltaic array cannot be adjusted in time when the environmental condition changes drastically in the prior art, so that the photovoltaic power generation power loss is high and the like are solved.

Description

Technical Field

[0001] This invention relates to the field of power technology control, and in particular to a method and device for maximum power point tracking of a photovoltaic array. Background Technology

[0002] With the continuous development of the global economy and the ongoing population growth, traditional non-renewable energy sources (coal, oil, natural gas, etc.) are becoming increasingly depleted. The harmful gases such as nitrogen oxides and sulfur oxides produced during their combustion have posed a serious threat to human life and the ecological environment. Solar energy, as an abundant, clean, and pollution-free renewable energy source, has become one of the important ways to solve the energy crisis. Photovoltaic power generation systems directly convert solar radiation energy into electrical energy through the photovoltaic effect of semiconductor devices, and are currently the mainstream form of solar energy utilization.

[0003] However, the output power of photovoltaic arrays exhibits strong nonlinear characteristics, with their current-voltage (IV) and power-voltage (PV) characteristic curves dynamically drifting with real-time changes in ambient temperature and solar irradiance. To maximize solar energy utilization, the industry commonly introduces Maximum Power Point Tracking (MPPT) technology into photovoltaic grid-connected inverters or stand-alone power generation systems. This technology adjusts the operating point of the load or converter in real time, ensuring that the photovoltaic array always operates near its maximum power point (MPP).

[0004] Among existing MPPT algorithms, the Perturb & Observe (P&O) method has been widely used in industrial photovoltaic inverters due to its advantages such as simple algorithm structure, low implementation cost, low requirements for sensor accuracy, and fast tracking speed. The basic principle of the P&O method is to apply a small perturbation of fixed amplitude to the operating voltage of the photovoltaic array in each sampling period, and determine the direction of the next perturbation by comparing the change in output power before and after the perturbation, thereby gradually approximating the MPP.

[0005] Although the P&O method can achieve good tracking results under steady-state illumination conditions, it still has the following insurmountable drawbacks in actual operating environments: 1. It is difficult to achieve both tracking speed and steady-state accuracy. The perturbation step size ΔU directly determines the dynamic response speed and steady-state power oscillation amplitude of the P&O method. If ΔU is large, the system can quickly approach the MPP, but significant power oscillations will occur near the MPP due to overshoot, resulting in energy loss. If ΔU is small, although it can effectively suppress steady-state oscillations, it significantly prolongs the tracking time. Especially in scenarios with sudden changes in irradiance, the system cannot track the new MPP in time, resulting in power generation loss.

[0006] 2. High sensitivity to environmental changes Traditional P&O methods typically assume that ambient irradiance remains constant or changes linearly within a sampling period Ts. However, due to factors such as cloud cover, dust accumulation, and changes in the sun's angle, irradiance often exhibits nonlinearity and rapid fluctuations. When irradiance changes drastically, the perturbation direction judgment based on the power-voltage information of the previous period is prone to misjudgment, causing the operating point to deviate from the true MPP, or even producing a "direction reversal" phenomenon, further reducing system efficiency and stability.

[0007] Therefore, how to improve the existing technology's inability to adjust the maximum output power of the photovoltaic array in a timely manner under drastic changes in environmental conditions, resulting in high photovoltaic power loss, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] Based on this, the purpose of this application is to provide a maximum power point tracking method and device for a photovoltaic array to solve at least one of the technical problems mentioned in the background art.

[0009] In a first aspect, this application provides a maximum power point tracking method for a photovoltaic array, comprising: S1: Start the photovoltaic array until the current output voltage of the photovoltaic array is in the first range of the maximum power point; S2: Obtain the current power of the photovoltaic array and apply a perturbation voltage to obtain the updated power of the photovoltaic array; S3: Obtain the power-voltage slope based on the current power and the updated power, and determine whether the absolute value of the slope is less than the critical threshold. If not, calculate the updated disturbance voltage based on the current disturbance voltage and the slope, and return to step S2. If yes, determine the second range of the maximum power point based on the updated power and the current disturbance voltage, and select several distinct points within the second range to fit the maximum power point. The second range is smaller than the first range.

[0010] Further steps for starting the photovoltaic array include: S11: Start the photovoltaic array using the constant voltage method to obtain the open-circuit voltage; S12: Based on the open-circuit voltage and the preset voltage factor, set the voltage threshold to obtain the first range of the maximum power point; S13: Real-time acquisition of the current output voltage of the photovoltaic array and determination of whether it is less than the voltage threshold; S14: If yes, return to step S13; if no, determine that the current output voltage is within the first range of the maximum power point, and the startup is complete.

[0011] Further steps for obtaining the current power include: The current output voltage of the photovoltaic array is collected, and the power value of the photovoltaic array under the first light intensity and the second light intensity corresponding to the current output voltage is obtained to obtain the first power value and the second power value. The product of the light intensity factor and the second power value is obtained to get the light intensity power value; The difference between the light intensity power value and the first power value is obtained to get the predicted power value of the photovoltaic array under the current light intensity, which is the current power.

[0012] Furthermore, the step of obtaining the power-voltage slope based on the current power and the updated power includes: Based on step S2, the voltage and power before and after the disturbance are obtained; Obtain the power difference between the power before and after the disturbance, and the voltage difference between the output voltage before and after the disturbance; The ratio between the power difference and the voltage difference is obtained to get the power-voltage slope.

[0013] Furthermore, the step of calculating and updating the perturbation voltage based on the current perturbation voltage and slope includes: The normalized slope is obtained by multiplying the normalized coefficient by the slope. The step gain value is obtained by taking the square of the product of the steady-state coefficient and the slope. The normalized gain value is obtained by summing the normalized constant term and the step gain value. Obtain the ratio of the normalized slope to the normalized gain value to get the updated perturbation step size; The updated perturbation voltage is obtained based on the current perturbation voltage and the updated perturbation step size.

[0014] Furthermore, the step of obtaining the updated perturbation voltage based on the current perturbation voltage and the updated perturbation step size also includes: Determine whether the sign of the slope changes; If not, then the update perturbation step size is corrected using the search step size coefficient; if yes, then the update perturbation step size is corrected using the tracking step size coefficient; the corrected update perturbation step size is obtained; the search step size coefficient is greater than the tracking step size coefficient; Summing the current perturbation voltage and the corrected updated perturbation step size yields the updated perturbation voltage.

[0015] Furthermore, the step of determining a second range of the maximum power point based on the updated power and the current disturbance voltage includes: Using the updated power-corresponding voltage value as the center point and the current disturbance voltage as the radius, determine the second range of the maximum power point.

[0016] Furthermore, the step of randomly selecting several distinct points within the second range and fitting the data to obtain the maximum power point includes: S310: Select several voltage values ​​within the second range of the maximum power point, and collect the power values ​​of the photovoltaic array at each voltage value to obtain several sampling points; S311: Calculate the slope between each pair of adjacent sampling points and determine whether the signs are the same. If not, return to step S310 and obtain several sampling points again. If yes, obtain several distinct points, perform interpolation calculations based on each distinct point to obtain the voltage value corresponding to the maximum power point, collect the output power of the photovoltaic array at this voltage value, and obtain the maximum power point. If not, return to step S310.

[0017] Furthermore, after obtaining the maximum power point, it also includes: Real-time collection of current environmental parameters; determination of whether environmental parameters have changed; if not, leave them unchanged; if so, return to step S2.

[0018] Secondly, this application also provides a terminal device, including a memory and a processor; the memory stores program code executable by the processor; the program code is used to execute the maximum power point tracking method described in any one of the first aspects.

[0019] This invention provides a maximum power point tracking (MPPT) method and device for a photovoltaic (PV) array. The method comprises: S1: starting the PV array and tracking it until its current output voltage falls within a first range of the MPPT range, rapidly approaching the MPPT range to improve tracking efficiency; S2: acquiring the current power of the PV array and applying a perturbation voltage to obtain an updated power; S3: obtaining a power-voltage slope based on the current and updated power, and determining if the slope is less than a critical threshold; if not, calculating an updated perturbation voltage based on the current perturbation voltage and the slope, and returning to step S2; if yes, determining a second range of the MPPT range based on the updated power and the current perturbation voltage, and randomly selecting several distinct points within the second range to fit the MPPT point; since the second range is smaller than the first range, by dynamically adjusting the perturbation voltage based on real-time data and feedback, the PV array system can quickly respond to changes in the external environment, continuously iterate and update its power, and rapidly approach the MPPT range, thereby improving overall performance, tracking speed and steady-state accuracy, and reducing power loss. This solves the problem in existing technologies where the maximum output power of the PV array cannot be adjusted in a timely manner under drastic changes in environmental conditions, resulting in high power loss in PV generation. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the solar power generation system structure according to an embodiment of the present invention; Figure 2 This is a flowchart of the maximum power point tracking method according to an embodiment of the present invention; Figure 3 This is a flowchart of a maximum power point tracking method according to another embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the power acquisition effect of various methods according to embodiments of the present invention; Figure 5 This is a schematic diagram of the PU curves of the photovoltaic array under various light intensities according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the maximum power point and the maximum power range in an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that if the embodiments of the present invention involve directional indications, such as up, down, left, right, front, back, etc., these directional indications are only used to explain the relative positional relationships and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly. Furthermore, if the embodiments of the present invention involve descriptions such as "first," "second," "S1," "S2," "step one," "step two," etc., these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance, or implicitly indicating the number of technical features indicated or the order of method execution. Those skilled in the art will understand that anything that does not violate the inventive concept and is within the scope of the present invention should be included in the protection scope of the present invention.

[0023] Definitions: Photovoltaic arrays: A photovoltaic array is a system composed of multiple photovoltaic modules (such as solar panels) arranged in a specific pattern. It is used to convert solar energy into electrical energy and is typically used in applications such as... Figure 1 The solar power generation system shown can be installed on a roof, the ground, or other structures.

[0024] Maximum Power Point (MPP): The output characteristics of a photovoltaic (PV) module change with variations in the external environment and can be considered as a non-linear DC source. The external load significantly impacts the output power of the PV module. Under constant external conditions, the PV module's output power reaches its maximum only when the external load matches the internal resistance of the PV module. At this point, the PV module operates at the highest point of the PV curve, known as the Maximum Power Point (MPP).

[0025] Maximum Power Point Tracking (MPPT): Maximum power point tracking technology uses a suitable control unit to enable photovoltaic panels to continuously output the maximum effective power. In the practical application of photovoltaic power generation systems, in order to enable photovoltaic modules to output the most energy under any external environment, it is necessary to adjust the operating point of the photovoltaic modules according to the external environment and load conditions so that they always work near the MPP. This optimization process is called maximum power point tracking.

[0026] Perturbation and Observation (P&O): The perturbation and observation method uses a step search method. By applying a perturbation voltage to the output voltage of the photovoltaic cell, the direction of the perturbation voltage is adjusted by comparing the correlation between the output power of the port and the perturbation voltage, thereby achieving maximum power point tracking.

[0027] Constant Voltage Tracking (CVT): As an open-loop maximum power point tracking algorithm, the constant voltage method has a high tracking speed when tracking MPP and can quickly respond to changes in light and temperature. Compared with other complex control algorithms, it is relatively simple to implement and has a lower control cost.

[0028] like Figure 2 , Figure 3 As shown, this invention provides a maximum power point tracking method for photovoltaic arrays: S1: Start the photovoltaic array until the current output voltage of the photovoltaic array is in the first range of the maximum power point; Specifically, Constant Voltage Tracking (CVT), as an open-loop maximum power point tracking algorithm, has a high tracking speed when tracking MPP and can quickly respond to changes in light and temperature. Compared with other complex control algorithms, it is relatively simple to implement and has a lower control cost. When the output voltage of the photovoltaic array is far from the voltage corresponding to the maximum power point, it will affect the tracking efficiency of the maximum power point. It is best to perform subsequent tracking steps when the output voltage is close to the voltage corresponding to the maximum power point, which will greatly improve the tracking efficiency of the maximum power point. Therefore, it is optional, but not limited to, for those skilled in the art to set a first range of the maximum power point and start the photovoltaic array using Constant Voltage Tracking (CVT) until the current output voltage of the photovoltaic array is within the first range of the maximum power point, so as to improve the tracking efficiency.

[0029] Preferably, the step of starting the photovoltaic array until the current output voltage of the photovoltaic array is within a first range of the maximum power point may optionally include: S11: Start the photovoltaic array using the constant voltage method to obtain the open-circuit voltage; S12: Based on the open-circuit voltage and the preset voltage factor, set the voltage threshold to obtain the first range of the maximum power point; S13: Real-time acquisition of the current output voltage of the photovoltaic array and determination of whether it is less than the voltage threshold; S14: If yes, return to step S13; if no, determine that the current output voltage is within the first range of the maximum power point, and the startup is complete.

[0030] Specifically, a voltage factor can be optionally set, and the photovoltaic array can be started to obtain the open-circuit voltage Uoc. The product of the voltage factor and the open-circuit voltage Uoc is obtained as the voltage threshold. Optionally, a first range of the maximum power point can be set to be not less than the voltage threshold. Then, the current output voltage of the photovoltaic array is collected in real time, and it is determined whether it is less than the voltage threshold. If it is, the process returns to step S13 to continue collecting the current output voltage of the photovoltaic array in real time for further judgment. If not, it means that the current output voltage is within the first range of the maximum power point. At this time, the output power of the photovoltaic array is near the maximum power point, and the subsequent maximum power point tracking steps can be performed. The set conditions have been met, and the startup is complete. Preferably, the voltage factor is set to 0.8.

[0031] S2: Obtain the current power of the photovoltaic array and apply a perturbation voltage to obtain the updated power of the photovoltaic array; Specifically, an initial disturbance voltage can be set, and the voltage and current of the photovoltaic array can be collected before and after the disturbance to obtain the current power and updated power of the photovoltaic array.

[0032] Preferred, such as Figure 4 As shown, (a) represents the PV&O method's illuminance mutation tracking curve; (b) represents the regional illuminance mutation tracking curve; and (c) represents the power prediction method's illuminance mutation tracking curve. Because when environmental parameters such as illuminance or environmental conditions change abruptly, the power curve may oscillate and misjudge within a short period, resulting in an increased variance between the predicted power curve and the ideal power curve, thus affecting system stability. The figure shows that methods such as PV&Q experience prolonged output power oscillations during environmental mutations, making it impossible to accurately obtain the current power of the photovoltaic array. However, after applying a perturbation voltage, the oscillations decrease after a longer period from the mutation point. Therefore, before the iteration begins, the step of obtaining the current power may optionally include a correction phase, specifically including: S21: Collect the current output voltage of the photovoltaic array, obtain the power value of the photovoltaic array under the first light intensity and the second light intensity corresponding to the current output voltage, and obtain the first power value and the second power value. S22: Obtain the product of the light intensity factor and the second power value to get the light intensity power value; S23: Obtain the difference between the light intensity power value and the first power value to get the predicted power value of the photovoltaic array under the current light intensity, which is the current power.

[0033] Specifically, since a photovoltaic array is assembled from several photovoltaic modules, the prior PU curves of the photovoltaic array under various light intensities under standard operating conditions can be obtained based on the factory parameters of the photovoltaic modules. Then, the first light intensity and the second light intensity, as well as the light intensity factor P1, can be set according to the current light intensity. The current output voltage of the photovoltaic array is collected, and the power value of the photovoltaic array under the first light intensity and the second light intensity is obtained according to the prior PU curves. The first power value and the second power value are obtained, and the product of the light intensity factor and the second power value is obtained to obtain the light intensity power value. Then, the difference between the light intensity power value and the first power value is obtained to obtain the predicted power value of the photovoltaic array under the current light intensity, which is the current power.

[0034] Preferably, the power prediction value of the photovoltaic array under the current irradiance can be calculated according to power prediction formulas 2-1 and 2-2: P'(K) = KP(K2) - P(K1) 2-1 K = (W1 + W3) / W2² - 2 Wherein, P'(K) is the current power, P(K1) is the first power value, P(K2) is the second power value, K is the light intensity factor, W1 is the first light intensity, W2 is the second light intensity, and W3 is the current light intensity.

[0035] For example, such as Figure 5 As shown, the first illuminance can be optionally set to 800, corresponding to PU curve 1; the second illuminance to 1000, corresponding to PU curve 2; and the current illuminance to 1200, corresponding to PU curve 3. Based on curves 1 and 2, the first power value P(K) and the second power value P(K+1 / 2) corresponding to the current voltage value U(K) can be obtained. The power prediction formula can be expressed as Equation 2-3: P'(K) = 2P(K + 1 / 2) - P(K) 2-3 Where P'(K) is the current power.

[0036] S3: Obtain the power-voltage slope based on the current power and the updated power, and determine whether the slope is less than the critical threshold. If not, calculate the updated disturbance voltage based on the current disturbance voltage and the slope, and return to step S2. If yes, determine the second range of the maximum power point based on the updated power and the current disturbance voltage, and select several distinct points within the second range to fit the maximum power point. The second range is smaller than the first range.

[0037] Specifically, since the slope of the tangent line at the maximum power point on the PU curve is 0, a critical threshold can be set. Then, based on the current power and the updated power, the power-voltage slope is obtained. It is then determined whether the slope is less than the critical threshold. If it is, it means the updated power is very close to the maximum power point, meeting the requirement of fitting the maximum power point; otherwise, based on the current disturbance voltage U... old And the slope, calculate the voltage correction value, i.e., the disturbance step size α, and based on the current disturbance voltage U old Given the perturbation step size α, determine the updated perturbation voltage U. new Referring to Formula 3-1, return to step S2. Under the disturbance effect of the updated disturbance voltage, detect the updated power again and calculate the power-voltage slope based on the previous power. Until the slope is less than the critical threshold, it is determined that the updated power has reached the vicinity of the maximum power point. Then, determine the second range of the maximum power point based on the updated power and the current disturbance voltage, and select several distinct points within the second range to fit the maximum power point.

[0038] Specifically, the updated disturbance voltage calculation formula can be represented as 3-1: 3-1 in, To update the disturbance voltage, The current disturbance voltage, The perturbation step size.

[0039] Preferably, the step of obtaining the power-voltage slope based on the current power and the updated power includes: S31: Based on step S2, obtain the voltage and power before and after the disturbance; S32: Obtain the power difference between the power before and after the disturbance, and the voltage difference between the output voltage before and after the disturbance; S33: Obtain the ratio between the power difference and the voltage difference to get the power-voltage slope.

[0040] Specifically, according to step S2, the output voltage and power before and after the most recent disturbance can be obtained, so as to further calculate the power difference between the power before and after the disturbance, and the voltage difference between the voltage before and after the disturbance. Finally, the ratio between the power difference and the voltage difference can be obtained to get the power-voltage slope.

[0041] For example, the power-voltage slope can be calculated using equations 3-1, 3-2, and 3-3: k=dP / dU 3-1 dP = P2 - P13 - 2 dU=U2-U13-3 Where k is the power-voltage slope, dP is the voltage difference, dU is the power difference, P2 is the power value after the disturbance, P1 is the power value before the disturbance, U2 is the voltage value after the disturbance, and U1 is the voltage value before the disturbance.

[0042] Preferably, the step of calculating the updated perturbation voltage based on the current perturbation voltage and slope may include: S34: Obtain the product of the normalization coefficient and the slope to get the normalized slope; S35: Obtain the square of the product of the steady-state coefficient and the slope to get the step gain value; S36: Obtain the sum of the normalized constant term and the step gain value to get the normalized gain value; S37: Obtain the ratio of the normalized slope to the normalized gain value to get the updated perturbation step size; S38: Obtain the updated perturbation voltage based on the current perturbation voltage and the updated perturbation step size.

[0043] Specifically, to facilitate subsequent optimization of the perturbation step size, normalization coefficients, steady-state coefficients, and normalization constants can be set based on factors such as light intensity. First, the product of the normalization coefficient and the slope is obtained to normalize the slope, resulting in the normalized slope. Then, the square of the product of the steady-state coefficient and the slope is obtained to get the step size gain value. This allows control of nonlinearity intensity based on the steady-state coefficient, improving tracking speed and steady-state accuracy, which is beneficial for subsequent iterations of the perturbation step size. Finally, the sum of the normalization constant and the step size gain value is obtained to get the normalized gain value, thus yielding the normalized slope and... The ratio of the normalized gain values ​​is used to obtain the updated perturbation step size. Finally, the current perturbation voltage and the updated perturbation step size are summed to obtain the updated perturbation voltage. Based on real-time data feedback, the perturbation step size is dynamically adjusted and the perturbation voltage is continuously updated, enabling the photovoltaic array system to respond quickly to changes in the external environment and support the optimization iteration process. By continuously adjusting the perturbation step size and updating the perturbation voltage, the slope is evaluated to determine whether it has reached the critical slope, gradually approaching the vicinity of the maximum power point and reaching the optimal solution level. This can effectively improve the stability, reliability, and overall performance of the photovoltaic system.

[0044] Preferably, the formula for calculating the perturbation step size can be expressed as 3-4: 3-4 in, Let k be the updated perturbation step size, k be the slope, N be the normalization coefficient, n be the normalization constant term, and P be the steady-state coefficient. Preferably, N=2, n=1, and P=2.

[0045] Preferably, if the distance between the updated power and the maximum power point is large, a small updated perturbation step size will increase the number of iterations and iteration time, reducing tracking efficiency; if the distance between the updated power and the maximum power point is small, an excessively large perturbation step size will bypass the maximum power point and reach the other side of the parabola, reducing tracking accuracy. Therefore, the step of obtaining the updated perturbation voltage based on the current perturbation voltage and the updated perturbation step size may optionally further include: S381: Determine whether the sign of the slope changes; S382: If not, then the update perturbation step size is corrected by the search step size coefficient; if yes, then the update perturbation step size is corrected by the tracking step size coefficient; the corrected update perturbation step size is obtained; the search step size coefficient is greater than the tracking step size coefficient; S383: Sum the current disturbance voltage and the corrected updated disturbance step size to obtain the updated disturbance voltage.

[0046] Specifically, a search step size coefficient H and a tracking step size coefficient L can be optionally set. The tracking step size coefficient is greater than the search step size coefficient. Since the tangent line of the curve where the maximum power point is located is 0, the location of the maximum power point can be initially located based on the sign of the slope before and after iteration. When the sign of the slope changes, it indicates that the updated power has crossed the maximum power point. When the sign of the slope does not change, it indicates that the distance between the updated power and the current power and the maximum power point is far. Therefore, it is necessary to correct the update perturbation step size according to the search step size coefficient. By increasing the size of the perturbation step size, the tracking efficiency can be improved. When the sign of the slope changes, it indicates that the updated power has crossed the maximum power point and is approaching the vicinity of the maximum power point. Therefore, it is necessary to correct the update perturbation step size according to the tracking step size coefficient. By reducing the size of the perturbation step size, it is possible to avoid repeatedly crossing the maximum power point, increasing the number of iterations and reducing the tracking efficiency, while improving the tracking accuracy.

[0047] Preferably, the corrected updated perturbation step size can be obtained by multiplying the perturbation step size by the search step size coefficient, or by multiplying the perturbation step size by the tracking step size coefficient.

[0048] For example, the corrected update perturbation step size can be obtained according to Equation 3-5: 3-5 in, The corrected update perturbation step size is defined by H, where H is the search step size coefficient and L is the tracking step size coefficient. Therefore, based on whether the slope changes sign, different step size coefficients are selectively used to further adjust the perturbation step size, balancing tracking efficiency and accuracy.

[0049] Preferably, the step of determining the second range of the maximum power point based on the updated power and the current disturbance voltage includes: S39: Determine the second range of the maximum power point with the updated power corresponding voltage value as the center point and the current disturbance voltage as the radius; Specifically, when the power-voltage slope is less than the critical threshold, it means that the updated power has approached the maximum power point. At this time, the voltage value corresponding to the updated power can be selected as the center point and the current disturbance voltage as the radius to determine the second range of the maximum power point. The second range is smaller than the first range.

[0050] More specifically, let the update voltage corresponding to the update power be U1, and the current disturbance voltage be U1. The second range can be represented as [U1+ U1- ].

[0051] S310: Select several voltage values ​​within the second range of the maximum power point, and collect the power values ​​of the photovoltaic array at each voltage value to obtain several sampling points; S311: Calculate the slope between each pair of adjacent sampling points and determine whether the signs are the same. If not, return to step S310 and obtain several sampling points again. If yes, obtain several distinct points, perform interpolation calculations based on each distinct point to obtain the voltage value corresponding to the maximum power point, collect the output power of the photovoltaic array at this voltage value, and obtain the maximum power point. If not, return to step S310. Specifically, several voltage values ​​can be selected, but are not limited to, within the second range of the maximum power point. The power values ​​corresponding to the photovoltaic array at each voltage value are collected. Voltage is plotted on the x-axis, and power on the y-axis, resulting in several sampling points. The slope between each pair of adjacent sampling points is calculated, and the signs are checked. If they are the same, it indicates that all sampling points are located on one side of the maximum power point, with no distinct points, and the maximum power point cannot be obtained through interpolation. Several new sampling points need to be acquired until each sampling point is located on the left and right sides of the maximum power point. If not, it indicates that each sampling point is located on the left and right sides of the maximum power point, with distinct points, satisfying the set conditions. Preferably, interpolation is performed using the Lagrange interpolation function to fit the voltage value of the maximum power point. Then, the output power of the photovoltaic array at that voltage value is collected to obtain the maximum power point. Preferably, the number of sampling points is 3.

[0052] For example, such as Figure 6 As shown, the three hollow points obtained in step S310 can be selected as sampling points, with coordinates represented as (x0, y0), (x1, y1), and (x2, y2), respectively, where x is voltage and y is power. Then, the Lagrange interpolation function can be expressed as Equation 3-6: 3-6 Where, x maxLet k1(x), k2(x), and k3(x) be the voltage values ​​corresponding to the maximum power point, and k1(x), k2(x), and k3(x) be Lagrange polynomials, defined as shown in equations 3-7, 3-8, and 3-9:

[0053] Then, by substituting the coordinates of each sampling point into the interpolation function, the voltage value x corresponding to the maximum power point can be calculated. max =U m Finally, by collecting the output power of the photovoltaic array at this voltage value, the coordinates of the maximum power point P can be obtained. max (U m P m ).

[0054] Furthermore, as the sun rises and sets and clouds move, environmental conditions change constantly. When environmental conditions change, the power curve of the photovoltaic array also changes. Therefore, after obtaining the maximum power point, it is necessary to collect environmental parameters in real time to determine whether the environmental conditions have changed and update the maximum power point in a timely manner.

[0055] S312: Collect current environmental parameters in real time and determine whether the environmental parameters have changed. If not, they remain unchanged; if so, return to step S2.

[0056] Specifically, the system can optionally, but is not limited to, real-time acquisition of environmental parameters such as current light intensity or temperature. When the sensor detects a change in environmental parameters, it indicates that the change in environmental parameters has already affected the photovoltaic array. The sensor can be used to determine whether the environmental parameters have changed. If not, it means that the environmental conditions have not changed, and the output power of the photovoltaic array is still at the maximum power point. If yes, it means that the environmental conditions have changed, and therefore the power curve of the photovoltaic array has also changed. It is necessary to return to step S2 and reacquire the maximum power point.

[0057] This embodiment presents a maximum power point tracking (MPPT) method for a photovoltaic (PV) array according to the present invention. The method involves: S1: starting the PV array and tracking it until its current output voltage falls within a first range of the MPPT range, quickly approaching the MPPT range to improve tracking efficiency; S2: acquiring the current power of the PV array and applying a perturbation voltage to obtain an updated power; S3: obtaining a power-voltage slope based on the current power and the updated power, and determining whether the slope is less than a critical threshold; if not, calculating an updated perturbation voltage based on the current perturbation voltage and the slope, and returning to step S2; if yes, determining a second range of the MPPT range based on the updated power and the current perturbation voltage, and randomly selecting several distinct points within the second range to fit the MPPT point; since the second range is smaller than the first range, by dynamically adjusting the perturbation voltage based on real-time data and feedback, the PV array system can quickly respond to changes in the external environment, continuously iterate and update the power, and rapidly approach the MPPT range, thereby improving overall performance, increasing the tracking speed and steady-state accuracy of the PV array, and reducing power loss. This solves the problem in existing technologies where the maximum output power of the PV array cannot be adjusted in a timely manner under drastic changes in environmental conditions, resulting in high power loss in PV generation.

[0058] On the other hand, the present invention also provides a terminal device, including a memory and a processor; the memory stores program code that can be executed by the processor; the program code is used to execute any of the above-described maximum power point tracking methods.

[0059] For example, the program code can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the program code in the terminal device.

[0060] The terminal device can be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and memory. Those skilled in the art will understand that the terminal device may also include input / output devices, network access devices, buses, etc.

[0061] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0062] The memory can be an internal storage unit of the terminal device, such as a hard drive or RAM. The memory can also be an external storage device of the terminal device, such as a plug-in hard drive, SmartMedia Card (SMC), Secure Digital (SD) card, or Flash Card. Furthermore, the memory can include both internal and external storage units of the terminal device. The memory is used to store the program code and other programs and data required by the terminal device. The memory can also be used to temporarily store data that has been output or will be output.

[0063] The computer storage medium and terminal device described above are created based on the maximum power point tracking method described above. Their technical functions and beneficial effects will not be elaborated here. The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for maximum power point tracking of a photovoltaic array, characterized in that, include: S1: Start the photovoltaic array until the current output voltage of the photovoltaic array is in the first range of the maximum power point; S2: Obtain the current power of the photovoltaic array and apply a perturbation voltage to obtain the updated power of the photovoltaic array; S3: Obtain the power-voltage slope based on the current power and the updated power, and determine whether the absolute value of the slope is less than the critical threshold. If not, calculate the updated disturbance voltage based on the current disturbance voltage and the slope, and return to step S2. If yes, determine the second range of the maximum power point based on the updated power and the current disturbance voltage, and select several distinct points within the second range to fit the maximum power point. The second range is smaller than the first range.

2. The method according to claim 1, characterized in that, The steps to start up a photovoltaic array include: S11: Start the photovoltaic array using the constant voltage method to obtain the open-circuit voltage; S12: Based on the open-circuit voltage and the preset voltage factor, set the voltage threshold to obtain the first range of the maximum power point; S13: Real-time acquisition of the current output voltage of the photovoltaic array and determination of whether it is less than the voltage threshold; S14: If yes, return to step S13; if no, determine that the current output voltage is within the first range of the maximum power point, and the startup is complete.

3. The method according to claim 1, characterized in that, The steps to obtain the current power include: The current output voltage of the photovoltaic array is collected, and the power value of the photovoltaic array under the first light intensity and the second light intensity corresponding to the current output voltage is obtained to obtain the first power value and the second power value. The product of the light intensity factor and the second power value is obtained to get the light intensity power value; The difference between the light intensity power value and the first power value is obtained to get the predicted power value of the photovoltaic array under the current light intensity, which is the current power.

4. The method according to claim 3, characterized in that, The steps for obtaining the power-voltage slope based on the current power and the updated power include: Based on step S2, the voltage and power before and after the disturbance are obtained; Obtain the power difference between the power before and after the disturbance, and the voltage difference between the output voltage before and after the disturbance; The ratio between the power difference and the voltage difference is obtained to get the power-voltage slope.

5. The method according to claim 1, characterized in that, The steps for calculating the updated perturbation voltage based on the current perturbation voltage and slope include: The normalized slope is obtained by multiplying the normalized coefficient by the slope. The step gain value is obtained by taking the square of the product of the steady-state coefficient and the slope. The normalized gain value is obtained by summing the normalized constant term and the step gain value. Obtain the ratio of the normalized slope to the normalized gain value to get the updated perturbation step size; The updated perturbation voltage is obtained based on the current perturbation voltage and the updated perturbation step size.

6. The method according to claim 5, characterized in that, The step of obtaining the updated perturbation voltage based on the current perturbation voltage and the updated perturbation step size also includes: Determine whether the sign of the slope changes; If not, then the update perturbation step size is corrected using the search step size coefficient; if yes, then the update perturbation step size is corrected using the tracking step size coefficient; the corrected update perturbation step size is obtained; the search step size coefficient is greater than the tracking step size coefficient; Summing the current perturbation voltage and the corrected updated perturbation step size yields the updated perturbation voltage.

7. The method according to claim 1, characterized in that, The step of determining the second range of the maximum power point based on the updated power and the current disturbance voltage includes: Using the updated power-corresponding voltage value as the center point and the current disturbance voltage as the radius, determine the second range of the maximum power point.

8. The method according to claim 1, characterized in that, The steps for fitting the maximum power point by randomly selecting several distinct points within the second range include: S310: Select several voltage values ​​within the second range of the maximum power point, and collect the power values ​​of the photovoltaic array at each voltage value to obtain several sampling points; S311: Calculate the slope between each pair of adjacent sampling points and determine whether the signs are the same. If not, return to step S310 and obtain several sampling points again. If yes, obtain several distinct points, perform interpolation calculations based on each distinct point to obtain the voltage value corresponding to the maximum power point, collect the output power of the photovoltaic array at this voltage value, and obtain the maximum power point. If not, return to step S310.

9. The method according to claim 8, characterized in that, After obtaining the maximum power point, it also includes: Real-time collection of current environmental parameters; determination of whether environmental parameters have changed; if not, then remain unchanged; if so, return to step S2.

10. A terminal device, characterized in that, It includes a memory and a processor; the memory stores program code that can be executed by the processor; the program code is used to execute the maximum power point tracking method according to any one of claims 1 to 9.

Images