Method and apparatus for maximum power point tracking of a photovoltaic array

Abstract

The application relates to a maximum power point tracking method and device of a photovoltaic array, which comprises the following 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, acquiring the current power of the photovoltaic array, and applying a perturbation voltage to obtain the updated power of the photovoltaic array; S3, obtaining the power-voltage slope according to the current power and the updated power, and judging whether the slope is less than a critical threshold value; if not, calculating the updated perturbation voltage according to the current perturbation voltage and the slope, and returning to step S2; if yes, determining a second range of the maximum power point according to the updated power and the current perturbation voltage, and optionally selecting several different points in the second range to fit the maximum power point; and the second range is smaller than the first range. The application solves the problem that the prior art cannot timely adjust the maximum output power of the photovoltaic array under the condition that the environmental condition changes dramatically, and the photovoltaic power generation power loss is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power technology control, in particular to a maximum power point tracking method and device for a photovoltaic array. BACKGROUND

[0002] With the continuous development of global economy and the growing population, traditional non-renewable energy (coal, oil, natural gas, etc.) is becoming increasingly exhausted, and harmful gases such as nitrogen oxides and sulfur oxides produced in the combustion process have posed a serious threat to human life safety and the ecological environment. As a renewable energy source with abundant reserves and no pollution, solar energy has become one of the important ways to solve the energy crisis. Photovoltaic power generation systems convert solar radiation energy directly into electrical energy through the photovoltaic effect of semiconductor devices, which is the mainstream form of solar energy utilization at present.

[0003] However, the output power of the photovoltaic array has strong nonlinear characteristics, and its current-voltage (I-V) and power-voltage (P-V) characteristic curves dynamically drift with real-time changes in environmental temperature and solar irradiance. In order to maximize the utilization of solar energy, the industry generally introduces maximum power point tracking (MPPT) technology in photovoltaic grid-connected inverters or independent power generation systems to adjust the operating point of the load or converter in real time, so that the photovoltaic array always operates near the maximum power point (MPP).

[0004] In existing MPPT algorithms, the perturb and observe (P&O) method has been widely used in industrial photovoltaic inverters due to its simple algorithm structure, low implementation cost, low requirement for sensor accuracy, fast tracking speed, and other advantages. The basic principle of the P&O method is to apply a small perturbation of a 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 output power changes before and after the perturbation, so as to gradually approach the MPP.

[0005] Although the P&O method can achieve good tracking effect under stable light conditions, it still has the following defects that are difficult to overcome in actual operating environment:

[0006] 1. Difficulty in balancing tracking speed and steady-state accuracy

[0007] The perturbation step ΔU directly determines the dynamic response speed and steady-state power oscillation amplitude of the P&O method. If ΔU has a large value, the system can quickly approach the MPP, but in the vicinity of the MPP, there will be significant power oscillation due to over-regulation, resulting in energy loss; if ΔU has a small value, although it can effectively suppress steady-state oscillation, it significantly prolongs the tracking time, especially in the case of sudden changes in irradiance, the system cannot track the new MPP in time, causing loss of power generation.

[0008] 2. High sensitivity to environmental changes

[0009] The conventional P&O method usually assumes that the environmental irradiance remains constant or changes linearly within one sampling period Ts. However, due to factors such as cloud cover, dust accumulation, and changes in the angle of the sun, the irradiance often fluctuates nonlinearly and rapidly. When the irradiance changes dramatically, the disturbance direction determined based on the power-voltage information of the previous period is prone to misjudgment, causing the operating point to deviate from the true MPP, and even causing the "direction reversal" phenomenon, further reducing the system efficiency and stability.

[0010] Therefore, how to improve the prior art to adjust the maximum output power of the photovoltaic array in time under the condition that the environmental condition changes dramatically, and to reduce the loss of photovoltaic power generation power and other problems are technical problems to be solved in this field. SUMMARY

[0011] Based on this, the purpose of the present application is to provide a photovoltaic array maximum power point tracking method and device to solve at least one of the technical problems mentioned in the background art.

[0012] In a first aspect, the present application provides a photovoltaic array maximum power point tracking method, comprising:

[0013] S1: starting the photovoltaic array until the current output voltage of the photovoltaic array is located in a first range of the maximum power point;

[0014] S2: obtaining the current power of the photovoltaic array, and applying a disturbance voltage to obtain the updated power of the photovoltaic array;

[0015] S3: obtaining the power-voltage slope according to the current power and the updated power, and determining whether the absolute value of the slope is less than a critical threshold; if not, calculating the updated disturbance voltage according to the current disturbance voltage and the slope, and returning to step S2; if yes, determining the second range of the maximum power point according to the updated power and the current disturbance voltage, and fitting to obtain the maximum power point at several optional mutually different points in the second range; the second range is smaller than the first range.

[0016] Further, the step of starting the photovoltaic array comprises:

[0017] S11: starting the photovoltaic array by using the constant voltage method to obtain the open circuit voltage;

[0018] S12: setting a voltage threshold according to the open circuit voltage and a preset voltage factor to obtain the first range of the maximum power point;

[0019] S13: real-time acquisition of the current output voltage of the photovoltaic array, and determination of whether it is less than the voltage threshold;

[0020] S14: If yes, return to step S13; if no, determine that the current output voltage is located in the first range of the maximum power point, and start completion.

[0021] Further, the step of obtaining the current power comprises:

[0022] collecting the current output voltage of the photovoltaic array, obtaining the power values of the photovoltaic array under the first and second light intensities corresponding to the current output voltage, to obtain the first and second power values;

[0023] obtaining the product of the light intensity factor and the second power value to obtain the light intensity power value;

[0024] obtaining the difference between the light intensity power value and the first power value to obtain the power prediction value of the photovoltaic array under the current light intensity, as the current power.

[0025] Further, the step of obtaining the power-voltage slope according to the current power and the updated power comprises:

[0026] obtaining the voltage and power before and after the perturbation according to step S2;

[0027] obtaining the power difference between the power before and after the perturbation, and the voltage difference between the output voltages before and after the perturbation;

[0028] obtaining the ratio between the power difference and the voltage difference to obtain the power-voltage slope.

[0029] Further, the step of calculating the updated perturbation voltage according to the current perturbation voltage and the slope comprises:

[0030] obtaining the product of the normalization coefficient and the slope to obtain the normalized slope;

[0031] obtaining the square of the product of the steady-state coefficient and the slope to obtain the step gain value;

[0032] obtaining the sum of the normalization constant term and the step gain value to obtain the normalization gain value;

[0033] obtaining the ratio of the normalized slope and the normalization gain value to obtain the updated perturbation step;

[0034] obtaining the updated perturbation voltage according to the current perturbation voltage and the updated perturbation step.

[0035] Further, the step of obtaining the updated perturbation voltage according to the current perturbation voltage and the updated perturbation step further comprises:

[0036] determining whether the positive and negative signs of the slope change;

[0037] If not, the updated perturbation step is corrected by a search step coefficient; if yes, the updated perturbation step is corrected by a tracking step coefficient; a corrected updated perturbation step is obtained; the search step coefficient is greater than the tracking step coefficient;

[0038] The updated perturbation voltage is obtained by summing the current perturbation voltage and the corrected updated perturbation step.

[0039] Further, the step of determining the second range of the maximum power point according to the updated power and the current perturbation voltage comprises:

[0040] The second range of the maximum power point is determined with the updated power corresponding voltage value as a center point and the current perturbation voltage as a radius.

[0041] Further, the step of fitting the maximum power point by selecting several mutually different points in the second range comprises:

[0042] S310: several voltage values are selected in the second range of the maximum power point, and power values corresponding to the photovoltaic array under each voltage value are collected to obtain several sampling points;

[0043] S311: slopes between each two adjacent sampling points are calculated, and it is judged whether the signs are the same; if not, the step S310 is returned to obtain several sampling points again; if yes, several mutually different points are obtained, interpolation operation is performed according to each mutually different point to obtain a voltage value corresponding to the maximum power point, and the output power of the photovoltaic array under the voltage value is collected to obtain the maximum power point.

[0044] Further, after the maximum power point is obtained, the method further comprises:

[0045] The current environmental parameter is collected in real time, and it is judged whether the environmental parameter changes; if not, it is unchanged; if yes, the step S2 is returned.

[0046] In a second aspect, the application further provides a terminal device comprising 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 of any one of the first aspect.

[0047] The application provides a maximum power point tracking method and device of a photovoltaic array, which comprises the following steps: S1, starting the photovoltaic array until the current output voltage of the photovoltaic array is located in a first range of the maximum power point, rapidly approaching the vicinity of the maximum power point, and improving tracking efficiency; S2, obtaining the current power of the photovoltaic array, and applying a perturbation voltage to obtain the updated power of the photovoltaic array; S3, obtaining the power-voltage slope according to the current power and the updated power, and judging whether the slope is less than a critical threshold; if not, calculating the updated perturbation voltage according to the current perturbation voltage and the slope, and returning to step S2; if yes, determining a second range of the maximum power point according to the updated power and the current perturbation voltage, and fitting the maximum power point by selecting several different points in the second range; the second range is smaller than the first range, the perturbation voltage is dynamically adjusted according to real-time data and feedback, the photovoltaic array system can quickly respond to external environmental changes, the updated power is iterated and updated continuously, the maximum power point is rapidly approached, the overall performance is improved, the tracking speed and steady-state accuracy of the photovoltaic array are improved, and the power loss is reduced. The problems that the maximum output power of the photovoltaic array cannot be adjusted in time under the condition that the environmental condition changes greatly in the prior art, and the photovoltaic power generation power loss is high are solved. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 A structure schematic diagram of a solar power generation system of an embodiment of the application;

[0049] Figure 2 A flowchart of a maximum power point tracking method of an embodiment of the application;

[0050] Figure 3 A flowchart of a maximum power point tracking method of another embodiment of the application;

[0051] Figure 4 A power acquisition effect schematic diagram of various methods of an embodiment of the application;

[0052] Figure 5 A P-U curve schematic diagram of a photovoltaic array under various light intensities of an embodiment of the application;

[0053] Figure 6 A maximum power point and a maximum power range schematic diagram of an embodiment of the application. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0055] It should be noted that if the embodiments of the present application involve directional indications, such as up, down, left, right, front, back, etc., the directional indications are only used to explain the relative position relationship, motion condition, etc. between the components in a certain posture, and if the certain posture changes, the directional indications will also change accordingly. In addition, if the embodiments of the present application involve descriptions such as "first, second", "S1, S2", "step one, step two" and the like, such descriptions are only for description purposes and cannot be understood as indicating or implying the relative importance of the indicated technical features or the number of indicated technical features or indicating the execution order of the method, etc. Any modification within the technical concept of the present application without deviating from the main points of the present application should be included in the protection scope of the present application.

[0056] Noun explanation:

[0057] Photovoltaic array: a photovoltaic array is a system composed of multiple photovoltaic components (such as solar panels, etc.) arranged in a certain manner, used to convert solar energy into electrical energy, usually used in solar power generation systems as shown in Figure 1 , which can be installed on roofs, ground or other structures.

[0058] Maximum power point (MPP): the output characteristics of a photovoltaic component will change with changes in the external environment, which can be regarded as a nonlinear DC source. The external load has a great influence on the output power of the photovoltaic component. In the case of constant external conditions, only when the external load matches the internal resistance of the photovoltaic component, the output power of the photovoltaic component will reach the maximum, at this time the photovoltaic component works at the highest point of the P-V curve, which is called the maximum power point (MPP).

[0059] Maximum power point tracking (MPPT): the maximum power point tracking technology is to realize the continuous output of the maximum effective power of the photovoltaic panel by using a suitable control unit. In the practical application of photovoltaic power generation system, in order to realize that the photovoltaic component can output the most energy in any external environment, it is necessary to adjust the working point of the photovoltaic component according to the external environment and load condition, so that it always works near the MPP. This optimization process is called maximum power point tracking.

[0060] Perturbation and observation (P&O): perturbation and observation uses step search method, by applying perturbation voltage to the output voltage of photovoltaic cell, comparing the correlation between port output power and perturbation voltage to adjust the direction of perturbation voltage, so as to realize maximum power point tracking.

[0061] Constant Voltage Tracking (CVT): As an open-loop maximum power point tracking algorithm, the constant voltage method has high tracking speed when tracking the MPP, can quickly respond to changes in light and temperature, is relatively simple to implement compared with other complex control algorithms, and has lower control cost.

[0062] As shown in Figure 2 , Figure 3 The present application provides a maximum power point tracking method for a photovoltaic array:

[0063] S1: Start the photovoltaic array until the current output voltage of the photovoltaic array is located in the first range of the maximum power point;

[0064] Specifically, as an open-loop maximum power point tracking algorithm, the constant voltage method has high tracking speed when tracking the MPP, can quickly respond to changes in light and temperature, is relatively simple to implement compared with other complex control algorithms, and has lower control cost. When the output voltage of the photovoltaic array is far from the corresponding voltage of the maximum power point, it will affect the tracking efficiency of the maximum power point. It is best to perform the subsequent tracking step when the output voltage is located near the corresponding voltage of the maximum power point, which will greatly improve the tracking efficiency of the maximum power point. Therefore, the first range of the maximum power point can be optionally but not limitedly set by a person skilled in the art, and the photovoltaic array is started by the constant voltage method until the current output voltage of the photovoltaic array is located in the first range of the maximum power point, so as to improve the tracking efficiency.

[0065] Preferably, the step of starting the photovoltaic array until the current output voltage of the photovoltaic array is located in the first range of the maximum power point can optionally include:

[0066] S11: Start the photovoltaic array by the constant voltage method to obtain the open circuit voltage;

[0067] S12: Set a voltage threshold according to the open circuit voltage and a preset voltage factor to obtain the first range of the maximum power point;

[0068] S13: Real-time acquisition of the current output voltage of the photovoltaic array and determination of whether it is less than the voltage threshold;

[0069] S14: If yes, return to step S13; if no, determine that the current output voltage is located in the first range of the maximum power point, and the starting is completed.

[0070] Specifically, the voltage factor can be optionally set, and the photovoltaic array is started to obtain the open circuit voltage Uoc, the product of the voltage factor and the open circuit voltage Uoc is the voltage threshold, the first range of the maximum power point not less than the voltage threshold is optionally set, and then the current output voltage of the photovoltaic array is collected in real time, and it is judged whether the current output voltage is less than the voltage threshold, if yes, the step S13 is returned, and the current output voltage of the photovoltaic array is continuously collected in real time, and the re-judgment is performed; if no, it is indicated that the current output voltage is located in the first range of the maximum power point, at this time, the output power of the photovoltaic array is located near the maximum power point, and the subsequent maximum power point tracking step can be performed, and the set condition is met, and the starting is completed. Preferably, the voltage factor is set to 0.8.

[0071] S2: obtaining the current power of the photovoltaic array, and applying a perturbation voltage to obtain the updated power of the photovoltaic array;

[0072] Specifically, the initial perturbation voltage can be optionally set, and the voltage and current of the photovoltaic array are collected before and after the perturbation to obtain the current power and the updated power of the photovoltaic array.

[0073] Preferably, as shown in Figure 4 As shown in the figure, (a) represents the VP&O method light intensity mutation tracking curve; (b) represents the regional method light intensity mutation tracking curve; (c) represents the power prediction method light intensity mutation tracking curve; since the power curve may cause oscillation and misjudgment in a short time when the environmental parameters or environmental conditions such as light intensity mutate, which is manifested as the variance between the predicted power curve and the ideal power curve increases, thereby affecting the stability of the system, it can be seen from the figure that the output power of the VP&Q method and the like will oscillate for a long time when the environment mutates, and the current power of the photovoltaic array cannot be accurately obtained, and after the perturbation voltage is applied, the oscillation is reduced for a long time away from the mutation time point. Therefore, before the iteration starts, the step of obtaining the current power can also include a correction stage, which specifically includes:

[0074] S21: collecting the current output voltage of the photovoltaic array, obtaining the power values of the photovoltaic array under the first light intensity and the second light intensity corresponding to the current output voltage, to obtain the first power value and the second power value;

[0075] S22: obtaining the product of the light intensity factor and the second power value to obtain the light intensity power value;

[0076] S23: obtaining the difference between the light intensity power value and the first power value to obtain the power prediction value of the photovoltaic array under the current light intensity, which is the current power.

[0077] 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.

[0078] 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:

[0079] P'(K) = KP(K2) - P(K1) 2-1

[0080] K = (W1 + W3) / W2² - 2

[0081] 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.

[0082] 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:

[0083] P'(K) = 2P(K + 1 / 2) - P(K) 2-3

[0084] Where P'(K) is the current power.

[0085] 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.

[0086] Specifically, since the tangent slope of the maximum power point on the P-U curve is 0, a critical threshold can be optionally set, and then the power-voltage slope is obtained according to the current power and the updated power, to determine whether the slope is less than the critical threshold. If yes, it indicates that the updated power has approached the maximum power point, and the requirement of fitting the maximum power point is met. If no, the voltage correction value, i.e. the perturbation step α, is calculated according to the current perturbation voltage U old and the slope, and the updated perturbation voltage U old is determined according to the current perturbation voltage U new and the perturbation step α, and the reference formula 3-1, and then returns to step S2. The updated power is detected again under the perturbation of the updated perturbation voltage, and the power-voltage slope is calculated according to the previous power. Until the slope is less than the critical threshold, it is determined that the updated power has reached the maximum power point. The maximum power point second range is determined according to the updated power and the current perturbation voltage, and a plurality of mutually different points in the second range are optionally selected to fit the maximum power point.

[0087] Specifically, the updated perturbation voltage calculation formula can be optionally expressed as 3-1:

[0088] 3-1

[0089] wherein, is the updated perturbation voltage, is the current perturbation voltage, is the perturbation step.

[0090] Preferably, the step of obtaining the power-voltage slope according to the current power and the updated power comprises:

[0091] S31: obtaining the voltage and power before and after the perturbation according to step S2;

[0092] S32: obtaining the power difference between the power before and after the perturbation, and the voltage difference between the output voltage before and after the perturbation;

[0093] S33: obtaining the ratio between the power difference and the voltage difference to obtain the power-voltage slope.

[0094] Specifically, according to step S2, the output voltage and power before and after the latest perturbation can be obtained to further calculate the power difference between the power before and after the perturbation, and the voltage difference between the voltage before and after the perturbation. Finally, the ratio between the power difference and the voltage difference is obtained, i.e. the power-voltage slope.

[0095] For example, the power-voltage slope can be calculated according to formula 3-1, 3-2 and 3-3:

[0096] k=dP / dU 3-1

[0097] dP = P2 - P1 - 2

[0098] dU = U2 - U1 - 3

[0099] wherein k is a power-voltage slope, dP is a voltage difference, dU is a power difference, P2 is a power value after perturbation, P1 is a power value before perturbation, U2 is a voltage value after perturbation, and U1 is a voltage value before perturbation.

[0100] Preferably, the step of calculating the updated perturbation voltage according to the current perturbation voltage and the slope can optionally include:

[0101] S34: obtaining a product of the normalization coefficient and the slope to obtain a normalized slope;

[0102] S35: obtaining a square of a product of the steady-state coefficient and the slope to obtain a step gain value;

[0103] S36: obtaining a sum of the normalization constant term and the step gain value to obtain a normalized gain value;

[0104] S37: obtaining a ratio of the normalized slope and the normalized gain value to obtain an updated perturbation step;

[0105] S38: obtaining an updated perturbation voltage according to the current perturbation voltage and the updated perturbation step.

[0106] Specifically, to facilitate the optimization of the subsequent perturbation step, the normalization coefficient, the steady-state coefficient, and the normalization constant term can be optionally set according to the light intensity factor and the like. First, a product of the normalization coefficient and the slope is obtained to realize normalization processing of the slope and obtain a normalized slope. Then, a square of a product of the steady-state coefficient and the slope is obtained to obtain a step gain value, so as to control the nonlinearity according to the steady-state coefficient, improve the tracking speed and the steady-state accuracy, and facilitate the subsequent iteration of the perturbation step. Next, a sum of the normalization constant term and the step gain value is obtained to obtain a normalized gain value. Thus, a ratio of the normalized slope and the normalized gain value is obtained to obtain an updated perturbation step. Finally, a sum of the current perturbation voltage and the updated perturbation step is obtained to obtain an updated perturbation voltage. Thus, the perturbation step is dynamically adjusted and the perturbation voltage is continuously updated according to real-time data feedback, so that the photovoltaic array system can quickly respond to external environmental changes, support the optimization iteration process, and gradually approach the vicinity of the maximum power point by continuously adjusting the perturbation step and updating the perturbation voltage, so as to evaluate whether the slope reaches the critical slope and achieve the best solution level, thereby effectively improving the stability, reliability, and overall performance of the system and the photovoltaic array.

[0107] Preferably, the perturbation step calculation formula can be optionally expressed as 3-4:

[0108] 3-4

[0109] wherein, is the updated perturbation step, k is the slope, N is the normalization coefficient, n is the normalization constant term, and P is the steady-state coefficient. Preferably, N = 2, n = 1, and P = 2.

[0110] Preferably, if the distance between the updated power and the maximum power point is far, then a smaller updated perturbation step will increase the iteration times and iteration time, and reduce the tracking efficiency. If the distance between the updated power and the maximum power point is close, then a too large perturbation step will bypass the maximum power point and reach the other side of the parabola, reducing the tracking accuracy. Therefore, according to the current perturbation voltage and the updated perturbation step, the step of obtaining the updated perturbation voltage can further include:

[0111] S381: determining whether the positive and negative signs of the slope change;

[0112] S382: if not, correcting the updated perturbation step with a search step coefficient; if yes, correcting the updated perturbation step with a tracking step coefficient; obtaining a corrected updated perturbation step; the search step coefficient is greater than the tracking step coefficient;

[0113] S383: summing the current perturbation voltage and the corrected updated perturbation step to obtain the updated perturbation voltage.

[0114] Specifically, the search step coefficient H and the tracking step coefficient L can be optionally set, and the tracking step coefficient is greater than the search step coefficient. Since the tangent of the curve where the maximum power point is located is 0, the position of the maximum power point can be preliminarily located according to the signs of the slopes before and after iteration. When the positive and negative signs of the slope change, it indicates that the updated power has passed the maximum power point. When the positive and negative signs of the slope do not change, it indicates that the distance between the updated power and the current power and the maximum power point is far, and therefore the updated perturbation step needs to be corrected according to the search step coefficient. By increasing the size of the perturbation step, the tracking efficiency is improved. When the positive and negative signs of the slope change, it indicates that the updated power has passed the maximum power point and is approaching the vicinity of the maximum power point, and therefore the updated perturbation step needs to be corrected according to the tracking step coefficient. By reducing the size of the perturbation step, it is avoided to repeatedly pass the maximum power point, the iteration times are increased, the tracking efficiency is reduced, and the tracking accuracy is improved.

[0115] Preferably, the product of the perturbation step and the search step coefficient is obtained to obtain the corrected updated perturbation step, or the product of the perturbation step and the tracking step coefficient is obtained to obtain the corrected updated perturbation step.

[0116] For example, the corrected updated perturbation step can be obtained according to formula 3-5:

[0117] 3-5

[0118] wherein, is the corrected update perturbation step, H is a search step coefficient, and L is a tracking step coefficient. Thus, according to whether the positive or negative sign of the slope changes, different step coefficients are selectively used to further adjust the perturbation step, taking into account the tracking efficiency and tracking accuracy.

[0119] Preferably, the step of determining the second range of the maximum power point according to the update power and the current perturbation voltage comprises:

[0120] S39: determining a second range of the maximum power point with the update power corresponding voltage value as a center point and the current perturbation voltage as a radius.

[0121] Specifically, when the power-voltage slope is less than the critical threshold, it indicates that the update power has approached the vicinity of the maximum power point, at which time the second range of the maximum power point can be determined with the update power corresponding voltage value as a center point and the current perturbation voltage as a radius, and the second range is smaller than the first range.

[0122] More specifically, let the update power corresponding update voltage be U1, and the current perturbation voltage be , then the second range can be selected to be [U1+ , U1- ].

[0123] S310: selecting several voltage values in the second range of the maximum power point and collecting the power values of the photovoltaic array corresponding to each voltage value to obtain several sampling points.

[0124] S311: calculating the slope between each pair of adjacent sampling points and judging whether the signs are the same, if not, returning to step S310 to obtain several sampling points again; if yes, obtaining several different points, performing interpolation operation according to each different point to obtain the voltage value corresponding to the maximum power point, collecting the output power of the photovoltaic array at the voltage value to obtain the maximum power point, and if not, returning to step S310.

[0125] Specifically, optional but not limited to a number of voltage values in the second range of the maximum power point, and the corresponding power values of the photovoltaic array under each voltage value are collected, to obtain a number of sampling points with voltage values as the horizontal coordinates and power values as the vertical coordinates, and the slopes between each adjacent sampling point are calculated to determine whether the signs are the same. If yes, it means that each sampling point is located on one side of the maximum power point, there is no mutual point, and the maximum power point cannot be obtained by difference operation, and a number of sampling points need to be re-acquired until each sampling point is located on the left and right sides of the maximum power point. If no, it means that each sampling point is located on the left and right sides of the maximum power point, there is a mutual point, and the set condition is met. Preferably, the voltage value of the maximum power point is fitted by interpolation operation according to the Lagrange interpolation function. Then the output power of the photovoltaic array under the voltage value is collected, and the maximum power point is obtained. Preferably, the number of sampling points is 3.

[0126] As shown in FIG. 3, the maximum power point P (U, P) of the photovoltaic array is obtained by the following steps. Figure 6 As shown in FIG. 3, the maximum power point P (U, P) of the photovoltaic array is obtained by the following steps.

[0127] 3-6

[0128] wherein, x max is the corresponding voltage value of the maximum power point, k1(x), k2(x), and k3(x) are Lagrange polynomials, and the definitions are shown in formula 3-7, 3-8, and 3-9.

[0129]

[0130] Then the coordinates of each sampling point are substituted into the interpolation function, and the voltage value x max of the maximum power point is calculated. m Finally, the output power of the photovoltaic array under the voltage value is collected, and the maximum power point coordinate P max (U m , P m ) is obtained.

[0131] Further preferably, with the natural phenomena such as the rising and setting of the sun and the movement of the cloud, the environmental conditions will change from time to time. When the environmental conditions change, the power curve of the photovoltaic array will also change accordingly. Therefore, after obtaining the maximum power point, the environmental parameters need to be collected in real time to determine whether the environmental conditions have changed and update the maximum power point in time.

[0132] S312: Real-time collection of current environmental parameters, judgment of whether the environmental parameters have changed, if no, then unchanged; if yes, return to step S2.

[0133] Specifically, but not limited to, real-time acquisition of current light intensity or temperature and other environmental parameters, when the sensor detects changes in environmental parameters, it means that changes in environmental parameters can affect the photovoltaic array. The sensor can be used to determine whether the environmental parameter has changed. If not, it means that the environmental conditions have not changed, and the output power of the photovoltaic array is at the maximum power point. If yes, it means that the environmental conditions have changed, so the power curve of the photovoltaic array has also changed, and it needs to return to step S2 to reacquire the maximum power point.

[0134] In this embodiment, a maximum power point tracking method of a photovoltaic array is provided. In the embodiment, the method comprises the following steps: S1: starting the photovoltaic array until the current output voltage of the photovoltaic array is in a first range of the maximum power point, quickly approaching the maximum power point, improving the tracking efficiency, S2: acquiring the current power of the photovoltaic array and applying a perturbation voltage to obtain an updated power of the photovoltaic array; S3: obtaining a power-voltage slope according to 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 according to the current perturbation voltage and the slope, and returning to step S2; if yes, determining a second range of the maximum power point according to the updated power and the current perturbation voltage, and optionally selecting a plurality of different points in the second range to fit the maximum power point; the second range is smaller than the first range. The perturbation voltage is dynamically adjusted according to real-time data and feedback, so that the photovoltaic array system can quickly respond to external environmental changes, continuously update the power, quickly approach the maximum power point, improve the overall performance, improve the tracking speed and steady-state accuracy of the photovoltaic array, and reduce the power loss. The problems of the prior art, such as the inability to adjust the maximum output power of the photovoltaic array in time when the environmental conditions change dramatically, resulting in high photovoltaic power loss, are solved.

[0135] In another aspect, the present application also provides a terminal device comprising a memory and a processor; the memory stores program code executable by the processor; the program code is used to execute any of the above maximum power point tracking methods.

[0136] Illustratively, 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 application. The one or more modules / units can be a series of computer program instruction segments capable of completing a specific function, which are used to describe the execution process of the program code in the terminal device.

[0137] The terminal device can be a desktop computer, a notebook computer, a palm computer, a cloud server, and the like. The terminal device can include, but is not limited to, a processor, a memory. Those skilled in the art can understand that the terminal device can also include an input / output device, a network access device, a bus, and the like.

[0138] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, and the like. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0139] The memory can be an internal storage unit of the terminal device, such as a hard disk or a memory. The memory can also be an external storage device of the terminal device, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, and the like. Further, the memory can include both the internal storage unit and the external storage device 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.

[0140] The computer storage medium and the terminal device described above are created based on the maximum power point tracking method described above, and the technical effects and advantages thereof will not be repeated here. The technical features of the above-described embodiments can be combined in any manner. To make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not contradict each other, they should be considered as falling within the scope of the present disclosure.

[0141] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the present application should be subject to the appended claims.

Claims

1. A method of maximum power point tracking for a photovoltaic array, characterized by, The method comprises the following steps: S1: starting the photovoltaic array until the current output voltage of the photovoltaic array is located in a first range of the maximum power point; S2: obtaining the current power of the photovoltaic array, and applying a perturbation voltage to obtain the updated power of the photovoltaic array; S3: obtaining the power-voltage slope according to the current power and the updated power, comprising: obtaining the voltage and power before and after the perturbation according to step S2; obtaining the power difference between the power before and after the perturbation, and the voltage difference between the output voltages before and after the perturbation; obtaining the ratio between the power difference and the voltage difference to obtain the power-voltage slope; determining whether the absolute value of the slope is less than a critical threshold value; if not, calculating the updated perturbation voltage according to the current perturbation voltage and the slope, and returning to step S2; if yes, determining a second range of the maximum power point according to the updated power and the current perturbation voltage, and fitting the maximum power point by selecting a plurality of mutually different points in the second range; the second range is smaller than the first range; the step of determining the second range of the maximum power point according to the updated power and the current perturbation voltage comprises: taking the voltage value corresponding to the updated power as the center point and the current perturbation voltage as the radius to determine the second range of the maximum power point; the step of fitting the maximum power point by selecting a plurality of mutually different points in the second range comprises: S310: selecting a plurality of voltage values in the second range of the maximum power point, and collecting the power values of the photovoltaic array corresponding to each voltage value to obtain a plurality of sampling points; S311: calculating the slope between each adjacent sampling point, determining whether the signs are the same, if not, returning to step S310 to obtain a plurality of sampling points again; if yes, obtaining a plurality of mutually different points, performing interpolation operation according to each mutually different point to obtain the voltage value corresponding to the maximum power point, collecting the output power of the photovoltaic array at the voltage value to obtain the maximum power point, if not, returning to step S310.

2. The method of claim 1, wherein, The step of starting the photovoltaic array comprises: S11: starting the photovoltaic array by using the constant voltage method to obtain the open circuit voltage; S12: setting the voltage threshold value according to the open circuit voltage and a preset voltage factor to obtain the first range of the maximum power point; S13: collecting the current output voltage of the photovoltaic array in real time, and determining whether it is less than the voltage threshold value; S14: if yes, returning to step S13; if not, determining that the current output voltage is located in the first range of the maximum power point, and the starting is completed.

3. The method of claim 1, wherein, The step of obtaining the current power comprises: collecting the current output voltage of the photovoltaic array, obtaining the power values of the photovoltaic array under the first light intensity and the second light intensity corresponding to the current output voltage to obtain the first power value and the second power value; obtaining the product of the light intensity factor and the second power value to obtain the light intensity power value; obtaining the difference between the light intensity power value and the first power value to obtain the power prediction value of the photovoltaic array under the current light intensity, which is the current power.

4. The method of claim 1, wherein, The step of calculating the updated perturbation voltage according to the current perturbation voltage and the slope comprises: obtaining the product of the normalization coefficient and the slope to obtain the normalized slope; obtaining the square of the product of the steady-state coefficient and the slope to obtain the step gain value; obtaining the sum of the normalization constant term and the step gain value to obtain the normalization gain value; obtaining a ratio of the normalized slope and the normalized gain value to obtain an updated perturbation step; obtaining an updated perturbation voltage according to the current perturbation voltage and the updated perturbation step.

5. The method of claim 4, wherein, The step of obtaining the updated perturbation voltage according to the current perturbation voltage and the updated perturbation step further comprises: determining whether the positive and negative signs of the slope change; if not, correcting the updated perturbation step with a search step coefficient; if yes, correcting the updated perturbation step with a tracking step coefficient; obtaining a corrected updated perturbation step; the search step coefficient is greater than the tracking step coefficient; summing the current perturbation voltage and the corrected updated perturbation step to obtain the updated perturbation voltage.

6. The method according to any one of claims 1 to 5, characterized in that, After obtaining the maximum power point, further comprising: collecting current environmental parameters in real time, determining whether the environmental parameters change, if not, remaining unchanged; if yes, returning to step S2.

7. A terminal device, characterized by comprising: comprising a memory and a processor; the memory stores program codes executable by the processor; the program codes are used to execute the maximum power point tracking method in any one of claims 1 to 6.

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