Maximum power tracking method and related device

Abstract

The invention discloses a maximum power tracking method and a related device, which can be used in the photovoltaic field, and the method comprises the steps: obtaining a local maximum power point and an initial maximum power point based on a constraint condition of the local maximum power point and a photovoltaic system parameter; determining a target maximum power point from the local maximum power points based on tangent lines of the power and voltage characteristic curve at the local maximum power points; in the axis interval of the initial maximum power point and the axis interval of the target maximum power point, tracking is carried out through a power tracking algorithm, and a first convergence value of the target maximum power point and a second convergence value of the initial maximum power point are obtained; a global maximum power point is determined based on a maximum of the first convergence value and the second convergence value. Therefore, the multi-peak problem can be well solved in the process of tracking the maximum power of the photovoltaic system.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to a maximum power point tracking method and related apparatus. Background Technology

[0002] With the widespread application of photovoltaic systems, their operational efficiency and safety have attracted increasing attention.

[0003] Partial shading in photovoltaic (PV) systems can cause a sharp drop in the light intensity received by some cells. The shaded cells become reverse-biased, ceasing to generate photocurrent and becoming a load on the PV system, impacting overall efficiency and threatening its operational safety. Currently, bypass diodes connected in parallel across the PV cells are typically used to address this issue, bypassing the shaded cells. However, with the introduction of bypass diodes, the number and location of bypassed cells change as the shaded area shifts, leading to continuous variations in the system's operating voltage. Different operating voltages correspond to different maximum power outputs, resulting in a multi-peak phenomenon on the PV characteristic curve. Existing maximum power point (MPPT) methods often get stuck in local optima on this multi-peak PV characteristic curve, failing to find the global maximum power point. Consequently, the PV system struggles to reach maximum power through voltage or current regulation, resulting in low energy conversion efficiency and high losses.

[0004] Therefore, finding the global maximum power point when the PV characteristic curve of a photovoltaic system exhibits a multi-peak phenomenon during operation has become a problem that needs to be solved. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a maximum power point tracking method and related apparatus, which can find the global maximum power point when the PV characteristic curve of a photovoltaic system exhibits a multi-peak phenomenon during operation.

[0006] The embodiments of this application disclose the following technical solutions:

[0007] In a first aspect, embodiments of this application provide a maximum power point tracking method, the method comprising:

[0008] Based on the constraints of the local maximum power point and the photovoltaic system parameters, the local maximum power point and the initial maximum power point are obtained; the initial maximum power point is the local maximum power point with the largest power value, and the power value of the initial maximum power point is the initial maximum power value.

[0009] Based on the tangent of the power and voltage characteristic curve at the local maximum power point, and the current and voltage characteristic curve, the target maximum power point is determined from the local maximum power point;

[0010] Within the axial interval of the initial maximum power point and within the axial interval of the target maximum power point, the power tracking algorithm is used to track the target maximum power point and the second convergence value of the initial maximum power point, respectively.

[0011] The global maximum power point is determined based on the maximum value between the first convergence value and the second convergence value.

[0012] Optionally, determining the target maximum power point from the local maximum power points based on the tangent line of the power-voltage characteristic curve at the local maximum power point and the current-voltage characteristic curve includes:

[0013] Based on the tangent line of the power and voltage characteristic curve at the local maximum power point, and the first voltage on the tangent line corresponding to the initial maximum power value, a first characteristic point is determined in the current and voltage characteristic curve.

[0014] Determine the second characteristic point corresponding to the local maximum power point on the current-voltage characteristic curve;

[0015] Calculate the slope of the line connecting the first feature point and the second feature point;

[0016] If the absolute value of the slope is less than a preset slope threshold, then the local maximum power point is determined as the target maximum power point.

[0017] Optionally, obtaining the initial maximum power point based on the constraints of the local maximum power point and the photovoltaic system parameters includes:

[0018] Based on the constraints of local maximum power points and photovoltaic system parameters, all local maximum power points are determined.

[0019] The local maximum power point with the largest power value among all local maximum power points is determined as the initial maximum power point.

[0020] Optionally, before determining the target maximum power point from the local maximum power point based on the tangent of the power-voltage characteristic curve at the local maximum power point and the current-voltage characteristic curve, the method further includes:

[0021] Based on the absolute value of the difference between the power value corresponding to each local maximum power point and the initial maximum power value, local maximum power points with an absolute difference greater than a preset threshold are removed.

[0022] Optionally, after determining the global maximum power point based on the maximum value of the first convergence value and the second convergence value, the method further includes:

[0023] If the absolute value of the difference between the real-time power and the power corresponding to the global maximum power point is greater than the first difference threshold, and the duration is greater than the first duration, then the global maximum power point is redefined.

[0024] Optionally, after determining the global maximum power point based on the maximum value of the first convergence value and the second convergence value, the method further includes:

[0025] If the number of iterations for the global maximum power point reaches the maximum number of iterations, then compare the current power and the historical power under the same voltage.

[0026] If the absolute value of the difference between the current power and the historical power is greater than the second difference threshold, then the global maximum power point is redefined.

[0027] Secondly, embodiments of this application provide a maximum power point tracking device, the device comprising: an acquisition module, a determination module, a calculation module, and an output module;

[0028] The acquisition module is used to acquire the local maximum power point and the initial maximum power point based on the constraints of the local maximum power point and the photovoltaic system parameters; the initial maximum power point is the local maximum power point with the largest power value, and the power value of the initial maximum power point is the initial maximum power value;

[0029] The determining module is used to determine a target maximum power point from the local maximum power points based on the tangent line of the power and voltage characteristic curve at the local maximum power point and the current and voltage characteristic curve.

[0030] The calculation module is used to track the target maximum power point and the target maximum power point respectively within the axial interval of the initial maximum power point and the axial interval of the target maximum power point using a power tracking algorithm, to obtain the first convergence value of the target maximum power point and the second convergence value of the initial maximum power point.

[0031] The output module is used to determine the global maximum power point based on the maximum value between the first convergence value and the second convergence value.

[0032] Optionally, the determining module includes a feature point determining unit, a slope calculation unit, and a target maximum power point determining unit;

[0033] The feature point determination unit is used to determine a first feature point in the current and voltage characteristic curve based on the tangent line of the power and voltage characteristic curve at the local maximum power point and the first voltage on the tangent line corresponding to the initial maximum power value; and to determine a second feature point corresponding to the local maximum power point on the current and voltage characteristic curve.

[0034] The slope calculation unit is used to calculate the slope of the line connecting the first feature point and the second feature point.

[0035] The target maximum power point determination unit is used to determine the local maximum power point as the target maximum power point when the absolute value of the slope is less than a preset slope threshold.

[0036] Thirdly, embodiments of this application provide a maximum power point tracking device, the device comprising: a memory and a processor;

[0037] The memory is used to store program code and transmit the program code to the processor;

[0038] The processor is configured to execute, according to the program code, the steps of the maximum power tracking method as described in any embodiment of the first aspect.

[0039] Fourthly, embodiments of this application provide a computer-readable storage medium storing a computer program that, when run on a maximum power tracking device, performs the steps of the maximum power tracking method as described in any embodiment of the first aspect.

[0040] This application provides a maximum power point tracking (MPPT) method. First, based on the constraints of the local maximum power points (MPPTs) of a photovoltaic (PV) system and the PV system parameters, local maximum power points within the intervals of each peak are determined from the power-voltage characteristic curves during the PV system's operation. The power-voltage characteristic curves have multiple peaks. Then, based on the voltage values ​​corresponding to each of the multiple local maximum power points, power tracking is performed using a power point tracking algorithm to obtain power convergence values ​​within the voltage intervals of each local maximum power point. These power convergence values ​​represent the maximum power within the voltage interval of the corresponding local maximum power point. Finally, the maximum value among the multiple power convergence values ​​is determined as the global maximum power point. Therefore, power tracking was performed using the perturbation-observation method for the local maximum power point corresponding to each peak in the PV characteristic curve. This allows us to obtain the actual maximum power of each peak in the PV characteristic curve, i.e., the convergence value corresponding to each peak. By taking the maximum value, we can obtain the global maximum power point. In the process of finding the global maximum power point, each peak of the PV characteristic curve is taken into account, which can avoid getting trapped in local optima and thus obtain a more accurate global maximum power point. This allows the photovoltaic system to reach maximum power through voltage regulation or current regulation, thereby improving the energy conversion efficiency of the photovoltaic system and reducing losses. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of partial shading in a photovoltaic system provided in an embodiment of this application;

[0043] Figure 2 A photovoltaic cell structure with an added bypass diode is provided in an embodiment of this application;

[0044] Figure 3 A flowchart of a maximum power point tracking method provided in this application embodiment;

[0045] Figure 4 A schematic diagram of an initial disturbance point provided in an embodiment of this application;

[0046] Figure 5 A flowchart of another maximum power point tracking method provided in this application embodiment;

[0047] Figure 6This is a schematic diagram illustrating the intersection of L1 and a local PV characteristic curve, provided in an embodiment of this application.

[0048] Figure 7 A schematic diagram illustrating the positional relationship between the tangent line of the PV characteristic curve at a local maximum power point and the initial maximum power value, provided for an embodiment of this application;

[0049] Figure 8 This is a schematic diagram illustrating a case where L1 and a local PV characteristic curve do not intersect, as provided in an embodiment of this application.

[0050] Figure 9 A schematic diagram of a maximum power point search process provided in an embodiment of this application;

[0051] Figure 10 A schematic diagram of a maximum power tracking device provided in an embodiment of this application;

[0052] Figure 11 This is a structural diagram of a maximum power tracking device provided in an embodiment of this application. Detailed Implementation

[0053] The maximum power point tracking method and related apparatus provided in this application can be used in the photovoltaic field. The above is only an example and does not limit the application field of the maximum power point tracking method and related apparatus provided in this application.

[0054] The terms "first," "second," "third," and "fourth," etc., used in this application specification, claims, and drawings are used to distinguish different objects, not to limit a specific order.

[0055] In the embodiments of this application, the terms "as an example" or "for example" are used to indicate that they are examples, illustrations, or explanations. Any embodiment or design that is described as "as an example" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design options. Specifically, the use of terms such as "as an example" or "for example" is intended to present the relevant concepts in a specific manner.

[0056] The terminology used in the implementation section of this application is for the purpose of explaining specific embodiments of this application only, and is not intended to limit this application.

[0057] See Figure 1 This figure is a schematic diagram of partial shading in a photovoltaic system according to an embodiment of this application. The photovoltaic (PV) system shown in the figure includes three photovoltaic cells PV1, PV2, and PV3 connected in series, and the IV characteristic curves of each photovoltaic cell. In the IV characteristic curves, I str This represents the series current of the three PVs, and MPP represents the maximum power point.

[0058] When PV1 and PV2 are under normal illumination, and PV3 is blocked, the light intensity received by PV3 decreases, causing the IV characteristic curve of PV3 to shift downwards on the I-axis. The current value at the intersection of the IV characteristic curve and the I-axis decreases, meaning the short-circuit current of PV3 decreases. str The current at the MPP point may be higher than that at PV3, or even as... Figure 1 I of PV3 str In situations where the current exceeds the short-circuit current, if only a portion of the PV cells (e.g., PV3) in a photovoltaic system is shaded, the unshaded PV cells (e.g., PV1 and PV2) remain exposed to sufficient sunlight. PV1 and PV2 will continue to generate current and voltage. Since the current in the series circuit is the same, the shaded PV3 cannot provide sufficient voltage to support the current flow. The voltage generated by PV1 and PV2 will be partially or fully applied to PV3, attempting to form a complete circuit path through PV3. This forces PV3 to bear the voltage from PV1 and PV2. Since the applied voltage to PV3 is opposite to its internal electric field, PV3 enters a reverse bias state, no longer generating photocurrent and unable to function as a power source, instead becoming a load in the photovoltaic system. In this case, the power consumed by PV3 is converted into heat, creating a hot spot effect.

[0059] To avoid hot spot effects, a bypass diode is typically connected in parallel with each PV, such as... Figure 2 .

[0060] Under normal operating conditions, the bypass diode is in reverse bias, and the voltage direction is opposite to the built-in electric field naturally formed by the PN junction inside the bypass diode. The bypass diode exhibits high impedance characteristics, and the current flowing through the bypass diode is close to zero, which does not affect the operation of the PV. When the PV is blocked, the blocked PV becomes a load. At this time, the bypass diode conducts, and the part of the branch current I that exceeds the photocurrent Iph of the blocked PV is shunted by the diode, thereby limiting the current and preventing the blocked PV from being damaged by hot spot effect. This situation is manifested as multiple power peaks on the PV characteristic curve.

[0061] Traditional maximum power point tracking (MPPT) algorithms include, but are not limited to, the perturb and observe (P&O) method, the incremental conductance (INC) method, and the hysteresis comparison method. Their principle is to seek the extreme point based on the mathematical characteristics of the PV characteristic curve. However, none of these algorithms possess a global perspective, are prone to getting trapped in local optima, and cannot solve the problem of multi-peak tracking.

[0062] Currently, in practical applications, to find the global maximum power value, a global scan of the IV characteristic curve is typically used, scanning the entire voltage range starting from the open-circuit voltage to obtain the global maximum power value. However, the global IV scan algorithm suffers from the problem of significant power fluctuations leading to capacity loss.

[0063] In view of this, embodiments of this application provide a maximum power point tracking (MPPT) method. First, based on the constraints of the local maximum power points (MPPTs) of the photovoltaic (PV) system and the PV system parameters, the local maximum power points within the voltage ranges of each peak are determined from the power-voltage characteristic curves during the PV system's operation. Next, based on the voltage values ​​corresponding to each of the multiple local maximum power points, power tracking is performed using a power point tracking algorithm to obtain the power convergence value within the voltage range of each local maximum power point. Finally, the maximum value among the multiple power convergence values ​​is determined as the global maximum power point. Thus, by first determining the local maximum power points within the voltage ranges of each peak, and then performing power tracking within a smaller voltage range of the local maximum power points using a power point tracking algorithm, it is unnecessary to perform power tracking across the entire voltage range. A simple algorithm can efficiently and accurately determine the global maximum power point, thereby enabling real-time adjustment of the PV system's operating parameters, such as voltage or current, to achieve the maximum power output of the PV system under the current operating voltage, reducing energy loss in the PV system.

[0064] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0065] See Figure 3 The figure is a flowchart of a maximum power point tracking method provided in an embodiment of this application. The method includes:

[0066] S301: Based on the constraints of the local maximum power point of the photovoltaic system and the parameters of the photovoltaic system, determine the local maximum power point within the voltage range where each peak is located from the power and voltage characteristic curves during the operation of the photovoltaic system.

[0067] A photovoltaic (PV) system consists of multiple PV cells connected in series. Each PV cell has a bypass diode connected in parallel across its terminals. When some PV cells are shaded, the shaded cells are bypassed by the parallel bypass diodes, resulting in a lower operating voltage compared to an unshaded system. The maximum power achievable by a PV system varies under different operating voltages. Consequently, the power-voltage characteristic curve (PV characteristic curve) of a PV system typically exhibits a multi-peak phenomenon, displaying multiple peaks.

[0068] As an example, the constraint condition for the local maximum power point is given by equation (1):

[0069]

[0070] Among them, V mppn This represents the voltage corresponding to the nth LMPP point in the photovoltaic system calculated under the standard linearity coefficient k. The linearity coefficient k is related to temperature and irradiance. The standard linearity coefficient k is calculated under an irradiance S = 1000 W / m². -2 s -1 Linearity coefficient in a standard test environment with an ambient temperature of T=25°C; V mpp-mod V represents the voltage corresponding to the maximum power point of a single PV module. oc-mod N represents the open-circuit voltage of a single PV module. s Indicates the number of PVs connected in series. Open-circuit voltage V oc-mod This can be found in the equipment manual, and corresponds to the voltage V at the maximum power point of a single PV module. mpp-mod A linear relationship exists; V can be determined based on the linear coefficient k. mpp-mod .

[0071] Photovoltaic system parameters include, but are not limited to, V mpp-mod V oc-mod , n and N s Parameters such as these.

[0072] Equation (1) is based on a hypothetical basic shading model, where each photovoltaic cell is shaded sequentially. n=1 corresponds to the first photovoltaic cell in a series being shaded, n=2 corresponds to the first and second photovoltaic cells in a series being shaded, and so on, until all photovoltaic cells are shaded. Equation (1) can be used to calculate the corresponding local maximum power point voltage for different shading conditions. Here, the first photovoltaic cell in a series refers to the photovoltaic cell through which the current first flows in the series chain.

[0073] With V′ mppn This represents the voltage corresponding to the nth LMPP point under actual operating conditions, with k' as the linearity coefficient under actual operating conditions and V as the linear coefficient. mppnLet represent the voltage corresponding to the nth LMPP point calculated under the standard linear coefficient k. The error of the result obtained by equation (1) can be expressed as equation (2):

[0074] e = V m p pn -V′ mpp n

[0075] =nkV oc-mod -0.7(N s -n)-(nk′V oc-mod -0.7(N s -n));

[0076] =n(kk′)V oc-mod

[0077] It is evident that when deviating from the standard test environment, as the number of PV series components increases or V oc-mod As the value increases, the error increases significantly. Therefore, the local maximum power point calculated directly using formula (1) has a large error compared to the actual local maximum power point in the photovoltaic system. The term with the largest power value in the local maximum power point is not necessarily the global maximum power point.

[0078] S302: Based on the voltage values ​​corresponding to each of the multiple local maximum power points, power tracking is performed using a power tracking algorithm to obtain the power convergence value within the voltage range of each of the multiple local maximum power points.

[0079] The power point tracking algorithm may include, but is not limited to, one or more of the following: P&O algorithm, incremental conductance method, hysteresis comparison method, interval search method, heuristic algorithms such as particle swarm optimization and differential evolution, curve fitting methods such as polynomial interpolation and spline interpolation, and intelligent algorithms such as fuzzy logic control. In this embodiment, the P&O algorithm is used as the power point tracking algorithm.

[0080] As an example, see Figure 4 The figure is a schematic diagram of an initial disturbance point provided in an embodiment of this application. In the figure, the upper part is the PV characteristic curve and the lower part is the IV characteristic curve. After calculating the voltage corresponding to all possible LMPP points of the photovoltaic system using equation (1), a large preset value can be subtracted from the voltage of each LMPP point to obtain multiple initial disturbance points as shown in the figure.

[0081] Therefore, within the same voltage range containing a peak, the voltage at the initial perturbation point is less than the voltage corresponding to the actual maximum power within that range. During the execution of the P&O algorithm, starting from each initial perturbation point, the voltage is increased sequentially to induce a perturbation. The voltage and corresponding current of each perturbation are recorded, and the corresponding power is calculated. This allows us to obtain the power convergence value within the voltage range containing each local maximum power point. The power convergence value represents the maximum power within the voltage range containing the corresponding local maximum power point. For a voltage range containing a local maximum power point, the minimum value is the voltage at the initial perturbation point corresponding to that local maximum power point, and the maximum value is the maximum value of the voltage range corresponding to the peak of the PV characteristic curve containing that local maximum power point.

[0082] For example, starting from an initial perturbation point, the P&O algorithm can be executed with a large step size of 1V. That is, each perturbation increases the voltage by 1V based on the voltage corresponding to the initial perturbation point. This can determine the voltage range with maximum power within the voltage range corresponding to the initial perturbation point, such as the voltage range of 15V to 16V. Then, the P&O algorithm can be executed with a small step size of 0.1V within the voltage range of 15V to 16V until the maximum power within the voltage range is found, and the power convergence value is obtained.

[0083] Alternatively, based on the voltage values ​​corresponding to each of the multiple local maximum power points, voltage intervals for each local maximum power point can be set, and the P&O algorithm can be executed in each voltage interval to obtain multiple power convergence values.

[0084] S303: Determine the maximum value among multiple power convergence values ​​as the global maximum power point.

[0085] Specifically, by comparing the magnitudes of multiple power convergence values, the maximum value among them can be determined. Since each power convergence value represents the actual maximum power within its voltage range, the maximum value among multiple power convergence values ​​is the global maximum power point.

[0086] Therefore, in this embodiment, the local maximum power point within the voltage range where each peak is located is first determined, and then power tracking is performed within a smaller voltage range where the local maximum power point is located using a power tracking algorithm. It is not necessary to perform power tracking within the entire voltage range. The global maximum power point can be determined efficiently and accurately through a simple algorithm, thereby enabling the photovoltaic system to reach the maximum power under the current operating voltage by adjusting the operating parameters such as voltage or current of the photovoltaic system in real time, thus reducing the energy loss of the photovoltaic system.

[0087] See Figure 5 The figure is a flowchart of another maximum power point tracking method provided in an embodiment of this application. The method includes:

[0088] S501: Based on the constraints of the local maximum power point of the photovoltaic system and the parameters of the photovoltaic system, determine the local maximum power point within the voltage range where each peak is located from the power and voltage characteristic curves during the operation of the photovoltaic system.

[0089] The power-voltage characteristic curve has multiple peaks.

[0090] S502: Based on the preset filtering rules and the initial maximum power point, select the local maximum power point that meets the filtering rules from multiple local maximum power points as the target maximum power point.

[0091] Specifically, the filtering rules are used to select local maximum power points whose power values ​​are close to those of the initial maximum power point; where the initial maximum power point is the local maximum power point with the largest corresponding power value.

[0092] Optionally, the difference between the initial maximum power value and each local maximum power point can be calculated, and the local maximum power point corresponding to the difference less than a preset threshold can be selected as the target maximum power point. Here, the initial maximum power value is the power value corresponding to the initial maximum power point; the preset threshold can be flexibly set based on actual needs.

[0093] Except for the initial maximum power point, the power values ​​of all local maximum power points are less than the initial maximum power value. It can be assumed that if the difference between the initial maximum power value and the corresponding power value of a local maximum power point is less than a preset threshold, a global maximum power point (GMPP) may exist within the voltage range of that local maximum power point. Further calculations are needed within such voltage ranges to find the GMPP. Conversely, if the difference between the initial maximum power value and the corresponding power value of a local maximum power point is greater than or equal to the preset threshold, the corresponding power value of that local maximum power point is much smaller than the initial maximum power value. Therefore, a GMPP cannot exist within its voltage range, and such voltage ranges can be ignored, removing these local maximum power points in subsequent calculations. For example, if the preset threshold is 20W and the initial maximum power value is 140W, then a local maximum power point with a power value greater than 120W is selected from multiple local maximum power points as the target maximum power point.

[0094] S503: Based on the voltage value corresponding to the target maximum power point and the voltage value corresponding to the initial maximum power point, power tracking is performed using the power tracking algorithm to obtain the power convergence value within the voltage range where the target maximum power point is located and the power convergence value within the voltage range where the initial maximum power point is located.

[0095] In this embodiment, the P&O algorithm is used as the power point tracking algorithm. As an example, a large preset value can be subtracted from the voltages corresponding to the initial maximum power point and each target maximum power point to obtain multiple initial perturbation points. Then, power tracking is performed using each initial perturbation point as the starting point for executing the P&O algorithm to obtain the power convergence value within the voltage range where the target maximum power point is located, as well as the power convergence value within the voltage range where the initial maximum power point is located.

[0096] Specifically, starting from the initial perturbation point, a large-step perturbation can be performed first to quickly determine the voltage range where the target maximum power point is located, and the tracking voltage range where the actual maximum power is located. Then, a small-step perturbation is performed to accurately track within multiple tracking voltage ranges. Within each tracking voltage range, the power converges to a single point, thus obtaining multiple power convergence values. This yields the power convergence value within the voltage range where the target maximum power point is located, as well as the power convergence value within the voltage range where the initial maximum power point is located.

[0097] Optionally, the P&O algorithm can be executed one by one for multiple target maximum power points to reduce the consumption of computing resources; or the P&O algorithm can be executed in parallel for multiple target maximum power points to improve the computing speed.

[0098] S504: Determine the maximum value among multiple power convergence values ​​as the global maximum power point.

[0099] Specifically, by comparing the magnitudes of multiple power convergence values, the maximum value among them can be determined. Since each power convergence value represents the actual maximum power within its voltage range, the maximum value among multiple power convergence values ​​is the global maximum power point.

[0100] Therefore, the P&O algorithm is only executed within the voltage range where the global maximum power point may exist to determine the GMPP point. This not only improves the efficiency of determining the GMPP point, but also maintains a high degree of recognition of the maximum power. Even if the power corresponding to the LMPP point is very close to the power corresponding to the GMPP point, the GMPP point can still be correctly identified.

[0101] S505: Determine whether the absolute value of the first difference between the real-time power value and the power value corresponding to the global maximum power point is greater than the first difference threshold. If yes, proceed to step S506; otherwise, repeat step S505.

[0102] After obtaining the global maximum power point, the operating parameters of the photovoltaic system, such as voltage or current, can be adjusted in real time based on the global maximum power point to make the real-time power of the photovoltaic system as close as possible to the global maximum power point, and the real-time power value of the photovoltaic system can be monitored.

[0103] Specifically, the absolute value of the difference between the real-time power value and the power value corresponding to the global maximum power point is calculated to obtain the first absolute value of the difference. If the first absolute value of the difference is greater than the first difference threshold, it indicates that the real-time power value deviates significantly from the power value corresponding to the global maximum power point. The photovoltaic system may be affected by changes in environmental conditions such as light intensity, causing a change in the global maximum power point of the photovoltaic system. In this case, step S506 needs to be executed to further determine whether the global maximum power point needs to be redefined. If the first absolute value of the difference is less than or equal to the first difference threshold, the deviation is within the normal range, and step S505 can be repeated for real-time judgment. The first difference threshold can be flexibly set based on actual needs.

[0104] S506: Determine whether the duration is greater than the first duration. If yes, proceed with step S501; otherwise, proceed with step S505.

[0105] Timing can begin when the absolute value of the first difference exceeds the first difference threshold. If the duration of this situation exceeds the first duration, it indicates that it is difficult to bring the deviation between the real-time power value and the global maximum power point back to the normal deviation range by adjusting the operating parameters of the photovoltaic system, such as current or voltage. In this case, the global maximum power point of the photovoltaic system may have changed, and steps S501 to S504 need to be executed to redetermine the global maximum power point. If the duration of this situation is less than or equal to the first duration, it indicates that the deviation between the real-time power value and the global maximum power point can automatically return to the normal deviation range, and the change in the global maximum power point of the photovoltaic system is small or has not changed. In this case, step S505 can be executed to continue real-time monitoring and judgment of the deviation between the real-time power value and the global maximum power point. The first duration can be flexibly set based on actual needs.

[0106] S507: Determine whether the number of iterations of the photovoltaic system operating point based on the global maximum power point has reached the maximum number of iterations. If yes, proceed to step S508; otherwise, proceed to step S507.

[0107] Specifically, after obtaining the global maximum power point (GMP), the operating point of the photovoltaic (PV) system can be changed, i.e., the operating parameters such as voltage or current of the PV system can be adjusted, so that the output power of the PV system approaches or even exceeds the global maximum power point. Each change in the operating point of the PV system is recorded as one iteration, and the power value of the PV system is recorded as the real-time power value. If the number of iterations reaches the maximum number of iterations, a considerable amount of time has passed since the last update of the global maximum power point, and factors such as changes in environmental conditions may affect the PV characteristic curve of the PV system, causing the global maximum power point to drift and change. In this case, step S508 needs to be executed to further determine whether the global maximum power point needs to be redefined. If the number of iterations is less than the maximum number of iterations, it can be considered that the global maximum power point has just been updated in a short period of time, and it is not necessary to redefine the global maximum power point. In this case, step S507 can be repeated to count the number of iterations. The maximum number of iterations can be flexibly set based on actual needs.

[0108] S508: Determine whether the absolute value of the second difference between the current power value and the historical power value under the same voltage is greater than the second difference threshold. If yes, proceed to step S501; otherwise, proceed to step S507.

[0109] Specifically, under the same voltage, the absolute value of the difference between the current power value and the historical power value is calculated to obtain the second absolute value of the difference. If the second absolute value of the difference is greater than the second threshold, the PV characteristic curve of the photovoltaic system can be considered to have drifted. In this case, steps S501 to S504 need to be executed to redetermine the global maximum power point. If the second absolute value of the difference is less than or equal to the second threshold, the PV characteristic curve of the photovoltaic system can be considered not to have drifted or to have drifted only slightly. In this case, it is not necessary to redetermine the global maximum power point, and step S507 can be executed again. Step S508 is executed after each subsequent iteration of the photovoltaic system operating point until it is determined that the global maximum power point needs to be redetermined; or step S507 can be executed again, and the number of photovoltaic system operating point iterations can be reset to zero and the count can be restarted. The second threshold can be flexibly set based on actual needs.

[0110] Alternatively, in another embodiment, step S502 may specifically be:

[0111] S5021: Based on the tangents of the power and voltage characteristic curves at each local maximum power point, determine the first voltage corresponding to the initial maximum power value in each tangent.

[0112] See Figure 6This figure is a schematic diagram illustrating the intersection of L1 and a local PV characteristic curve according to an embodiment of this application. The local PV characteristic curve refers to the PV characteristic curve within the m-axis range of the local maximum power point. In this figure, the upper half represents the PV characteristic curve of the photovoltaic system, and the lower half represents the IV characteristic curve of the photovoltaic system; both have the same voltage range.

[0113] Where L1 is a horizontal line drawn through the initial maximum power point n, and the power is equal everywhere on L1; point n is the initial maximum power point, and point m is the local maximum power point; L2 is the tangent line to the PV characteristic curve drawn through the local maximum power point m, and L1 and L2 intersect at point k1. The voltage corresponding to point k1 is the first voltage. For example, if the initial maximum power value is 140W, then the first voltage corresponding to the power value of 140W on the tangent line L1 is...

[0114] In this embodiment, a large preset value can be simultaneously subtracted from each local maximum power point, including the initial maximum power point, to obtain multiple initial disturbance points, and these initial disturbance points are used as local maximum power points in the calculation. Therefore, the voltages corresponding to the local maximum power points involved in the calculation are all lower than the voltages corresponding to the actual maximum power within the voltage range of their respective peaks. On the one hand, this facilitates the subsequent screening of target maximum power points by calculating the slope of the line connecting the feature points, improving the accuracy of the screening results. It avoids situations where the power of a local maximum power point is close to the initial maximum power, but the voltage of the local maximum power point is greater than the voltage corresponding to the actual maximum power within its voltage range, causing the second feature point x2 to be located in a region with a large rate of change of current in the IV characteristic curve. This makes it difficult to accurately determine whether a global maximum power point might exist within the voltage range of the local maximum power point by calculating the slope of the line connecting the two feature points. On the other hand, during the execution of the P&O algorithm, the voltage corresponding to the power convergence value is necessarily greater than the voltage corresponding to the local maximum power points involved in the calculation. There is no need to set the voltage range for executing the P&O algorithm. This avoids the inability to find the global maximum power point due to improper voltage range setting, and also allows for a smaller voltage range for executing the P&O algorithm, improving the power convergence speed.

[0115] S5022: By voltage mapping, from the current and voltage characteristic curves, corresponding to each tangent line, determine the first characteristic point corresponding to the first voltage and the second characteristic point corresponding to the local maximum power point voltage.

[0116] The voltage ranges of the current-voltage characteristic curve and the power-voltage characteristic curve are the same.

[0117] See Figure 7The figure is a schematic diagram of the positional relationship between the tangent line of the PV characteristic curve at a local maximum power point and the initial maximum power value provided in an embodiment of this application. In the figure, L1 is a horizontal line drawn through the initial maximum power point, and the power is equal everywhere on L1; L2 is the tangent line of the PV characteristic curve at the local maximum power point; L1 and L2 intersect at point k1, and a perpendicular line is drawn from point k1 to the voltage V axis, which intersects the PV characteristic curve at point k2.

[0118] When L1 intersects with the local PV characteristic curve where the local maximum power point is located, as shown in the left figure, k2 is located to the left of the local maximum power point; when L1 does not intersect with the local PV characteristic curve where the local maximum power point is located, as shown in the right figure, k2 is located to the right of the local maximum power point.

[0119] When L1 intersects with the local PV characteristic curve where the local maximum power point is located, see [reference needed]. Figure 6 Corresponding to the tangent L2, through voltage mapping, the first voltage corresponding to point k1 is mapped to the IV characteristic curve. In the IV characteristic curve, the point corresponding to the first voltage is the first characteristic point x1, and the first voltage of the first characteristic point x1 is V. k2 The first current is i k2 Map the second voltage corresponding to the local maximum power point m to the IV characteristic curve. In the IV characteristic curve, the point corresponding to the second voltage is the second characteristic point x2, and the first voltage of the second characteristic point x2 is V. m The first current is i m .

[0120] When L1 does not intersect with the local PV characteristic curve where the local maximum power point is located, see [reference needed]. Figure 8 In this figure, the local PV characteristic curve refers to the PV characteristic curve within the voltage V-axis interval at the local maximum power point m. The upper half of the figure shows the PV characteristic curve, and the lower half shows the V-axis characteristic curve. Point n is the initial maximum power point, and point m is the local maximum power point. L1 and L2 intersect at point k1. Corresponding to the tangent L2, a perpendicular line is drawn from point k1 to the voltage V-axis, intersecting the PV characteristic curve at point k2. k2 is to the right of k3, the point of maximum actual power value within the voltage interval corresponding to point m. The PV characteristic curve within the voltage interval at point m does not intersect L1, and the voltage value V at k3... k3 ∈[V m V k1 ], where V m Let V be the voltage at point m. k1 Let k1 be the voltage at point k. Draw a perpendicular line from k3 to the V-axis, intersecting the tangent line L2 at point m at k4.

[0121] By using voltage mapping, the first voltage corresponding to point k3 is mapped to the IV characteristic curve. In the IV characteristic curve, the point corresponding to the first voltage is the first characteristic point x1, and the first voltage of the first characteristic point x1 is V. k3 The first current is i k3 Map the second voltage corresponding to the local maximum power point m to the IV characteristic curve. In the IV characteristic curve, the point corresponding to the second voltage is the second characteristic point x2.

[0122] S5023: Calculate the slope of the line connecting the first feature point and the second feature point.

[0123] by Figure 6 Taking the corresponding situation as an example, according to the characteristics of the IV curve, the current change is very slow within the same interval. i.e. i m ≈i k2 ;

[0124] Depend on achievable

[0125] And because We can assume that point k1 can be approximately represented by point k2, thus obtaining equation (3): Among them, i n Let V be the current at point n. n Let n be the voltages at point n;

[0126] And because of V k2 =V k1 , with V k2 As a disturbance, the corresponding current i can be obtained. k2 Therefore, the slope g can be calculated using equation (4):

[0127] When L1 intersects with the local PV characteristic curve, the power at the local maximum power point is quite close to the initial maximum power value. Both characteristic points are located in the region where the current change is relatively gradual in the IV characteristic curve, so g should be a small value. However, it cannot be ruled out that there is a power greater than P on the curve near point m. n To determine the probability of a point, the LMPP within the intervals of points m and n needs to execute the P&O algorithm separately.

[0128] In such Figure 8 In the case shown where L1 does not intersect with the local PV characteristic curve, since the PV characteristic curve in the m interval conforms to the convex function characteristic, P k4 >P k3 V k4 =V k3 <V k1 And P k4 <P k1Therefore, we can conclude that: P k3 <P k1 That is, the maximum power point in this interval is less than P. n This interval can be discarded. In this case, the slope can be calculated using equation (4), resulting in a larger value of g.

[0129] S5024: Select the local maximum power point among multiple local maximum power points where the slope of the line connecting the first feature point and the second feature point is less than a preset slope threshold, and use it as the target maximum power point.

[0130] Specifically, the slope threshold can be set based on the actual situation. For example, the slope threshold can be set to 0.01.

[0131] If the slope of the line connecting the first feature point and the second feature point is less than a preset slope threshold, it indicates that the power of the corresponding local maximum power point is close to the initial maximum power value. Since there is an error between the theoretically calculated local maximum power point and the actual maximum power, the power convergence value within the voltage range of this local maximum power point may be greater than the power convergence value within the voltage range of the initial maximum power point. Therefore, it is necessary to further use the P&O algorithm to perform power tracking within both the voltage range of the local maximum power point and the voltage range of the initial maximum power point to determine the global maximum power point. Thus, the local maximum power point with a slope of less than the preset slope threshold is taken as the target maximum power point.

[0132] If the slope of the line connecting the first feature point and the second feature point is greater than or equal to the preset slope threshold, it indicates that the power of the corresponding local maximum power point is significantly different from the initial maximum power value. The power convergence value in the voltage range where it is located cannot be greater than the power convergence value in the voltage range where the initial maximum power point is located. Therefore, there is no need to further perform power tracking in the voltage range where the local maximum power point is located using the P&O algorithm.

[0133] Alternatively, in another embodiment, step S502 may specifically be:

[0134] First, calculate the difference between the initial maximum power value and each local maximum power point. Select the local maximum power point corresponding to the difference that is less than the preset threshold as the initial maximum power point. Then, perform steps S5021 to S5024 on each initial maximum power point to obtain the target maximum power point.

[0135] In another embodiment, the maximum power tracking method provided in this application will be described in conjunction with the examples shown in Tables 1 to 6 below.

[0136] See Table 1, which provides examples of photovoltaic system test conditions provided in the embodiments of this application:

[0137] Table 1 Photovoltaic System Test Conditions

[0138]

[0139]

[0140] In this embodiment, the theoretical maximum power of the photovoltaic system is 127.9W / 69.565V. By adjusting the operating point of the photovoltaic system under different operating conditions and measuring the actual power output of the photovoltaic system, the effectiveness of the maximum power point tracking (MPPT) method can be verified. Specifically, by adjusting the operating point of the photovoltaic system, an LMPP point of 126.7W / 49.511V was measured. This LMPP point is quite close to the theoretical maximum power, indicating that the maximum power point tracking method provided in this application has good performance, and the power convergence values ​​obtained for each voltage range are relatively accurate. Therefore, by adjusting the operating point, the output power of the photovoltaic system can be made closer to the theoretical maximum power.

[0141] The following is a detailed implementation of maximum power point tracking:

[0142] S1: Based on the constraints of the local maximum power point of the photovoltaic system and the parameters of the photovoltaic system, determine the local maximum power point within the voltage range where each peak is located from the power and voltage characteristic curves during the operation of the photovoltaic system.

[0143] See Table 2, which contains simulation parameters for the photovoltaic system provided in the embodiments of this application:

[0144] Table 2 Simulation parameters of the photovoltaic system

[0145]

[0146] Based on the parameters provided in Table 2, using equation (1):

[0147]

[0148] The voltage of the local maximum power point (LMPP) of the photovoltaic system in the five tests shown in Table 1 can be obtained, as shown in Table 3:

[0149] Table 3 All possible local maximum power points of the photovoltaic system

[0150] LMPP Calculate voltage value / V Corrected voltage value / V Current / A Power / W LMPP1 14.3 - - - LMPP2 32.1 30.1 3.866 116.903 LMPP3 49.9 47.9 2.608 125.06 LMPP4 67.7 65.7 1.872 123.024 LMPP5 84.4 84.4 0.752 63.527

[0151] In this regard, correcting the calculated voltage value to take into account actual factors can make the voltage value closer to the actual situation and improve the accuracy of subsequent calculations. For example, the corrected voltage value can be obtained through experimental data or on-site measurements.

[0152] S2: Calculate the difference between the initial maximum power value and the power value corresponding to each local maximum power point, and select the local maximum power point corresponding to the difference that is less than the preset threshold as the initial maximum power point.

[0153] Specifically, the power values ​​of all local maximum power points can be compared, and the one with the largest power value can be determined as the initial maximum power point. The power value of the initial maximum power point is the initial maximum power value. For example, in Table 3, the initial maximum power point is LMPP3, which has the largest power value.

[0154] Specifically, since the initial maximum power point is the local maximum power point with the largest power value, and the power values ​​of other local maximum power points are all less than the initial maximum power value, it can be assumed that when the difference between the initial maximum power value and the power value corresponding to the local maximum power point is greater than or equal to a preset threshold, the power value corresponding to the local maximum power point is much smaller than the initial maximum power value. It is impossible for a global maximum power point to exist in the voltage range in which it is located. Such a voltage range can be ignored, and the corresponding data in the voltage range can be deleted to reduce the amount of subsequent calculations.

[0155] If the difference between the initial maximum power value and the power value corresponding to the local maximum power point is less than the preset threshold, the power value corresponding to the local maximum power point is relatively close to the initial maximum power value. There may be a global maximum power point in the voltage range where it is located. Further calculation is needed in such a voltage range to determine the global maximum power point. Therefore, it is selected as the initial maximum power point.

[0156] For example, if the preset threshold is 10W and the initial maximum power value is 125.06W, then local maximum power points with power values ​​less than 115.06W will be removed from all local maximum power points, and the corresponding voltage, current, and power records will be deleted. See Table 4 for the preliminary screening results:

[0157] Table 4 Preliminary Screening Results

[0158]

[0159]

[0160] Among them, LMPP1 is an invalid test point; if the difference between the power value corresponding to LMPP3 and the power value corresponding to LMPP5 is greater than the preset threshold of 10W, the voltage, current and power corresponding to LMPP5 can be deleted, and LMPP2 and LMPP4 that meet the screening rules can be retained.

[0161] S3: Based on the tangents of the power and voltage characteristic curves at each local maximum power point, determine the first voltage corresponding to the initial maximum power value in each tangent.

[0162] In this embodiment of the application, the power corresponding to LMPP3 is taken as the initial maximum power V. n The initial maximum power V is set to the corrected voltage value corresponding to LMPP3. n The first voltage V can be calculated using the above formula (3). k As shown in Table 5:

[0163] Table 5 Calculation results of the first voltage

[0164]

[0165] S4: By voltage mapping, from the current and voltage characteristic curves, corresponding to each tangent line, determine the first characteristic point corresponding to the first voltage and the second characteristic point corresponding to the local maximum power point voltage.

[0166] Specifically, for LMPP2, the voltage at the first characteristic point x1 is the first voltage, i.e., 32.313V, and the current corresponding to the first voltage on the current-IV characteristic curve is, for example, 3.026A; the voltage at the second characteristic point x2 is the corrected voltage value corresponding to LMPP2, i.e., 30.1V, and the current is the current corresponding to LMPP2, i.e., 3.866A. For LMPP4, the voltage at the first characteristic point x1 is the first voltage, i.e., 66.732V, and the current corresponding to the first voltage on the current-IV characteristic curve is, for example, 1.869A; the voltage at the second characteristic point x2 is the corrected voltage value corresponding to LMPP4, i.e., 65.7V, and the current is the current corresponding to LMPP4, i.e., 1.872A.

[0167] S5: Calculate the slope of the line connecting the first feature point and the second feature point.

[0168] Specifically, using equation (4) above, the slope of the line connecting x1 and x2 can be calculated for LMPP2 and LMPP4 respectively, as shown in Table 6:

[0169] Table 6 Slope Calculation Results

[0170]

[0171] S6: Select the local maximum power point among multiple local maximum power points where the slope of the line connecting the first feature point and the second feature point is less than a preset slope threshold, and use it as the target maximum power point.

[0172] As an example, the slope threshold can be set to 0.01. In the slope calculation results shown in Table 6, the absolute value of the slope of LMPP2 is much greater than 0.01, so the voltage range where LMPP2 is located can be excluded; the absolute value of the slope of LMPP4 is less than 0.01, so the voltage range where LMPP4 is located cannot be excluded, and LMPP4 is taken as the target maximum power point.

[0173] S7: Based on the voltage value corresponding to the target maximum power point and the voltage value corresponding to the initial maximum power point, power tracking is performed using the power tracking algorithm to obtain the power convergence value within the voltage range where the target maximum power point is located and the power convergence value within the voltage range where the initial maximum power point is located.

[0174] As an example, a large-step P&O algorithm can be used to quickly determine the relationship between the actual maximum power points within the voltage ranges of the target maximum power point LMPP4 and the initial maximum power point LMPP3. For instance, using a large-step P&O algorithm for power point tracking, the approximate maximum power point of LMPP3 is found to be 49.989V / 126.189W, while the approximate maximum power point of LMPP4 is 69.6V / 127.907W. Since the power of LMPP4 is greater than that of LMPP3, a small-step P&O algorithm can be further executed only within the voltage range of LMPP4 to accurately track the global maximum power point.

[0175] like Figure 9 As shown in the figure, this figure is a schematic diagram of a maximum power point search process provided in an embodiment of this application. In this process, firstly, the LMPP axis is traversed to test the LMPP point position of the photovoltaic system under different operating conditions, and steps S1 to S3 are executed; then, a perturbation test is performed with the first voltage as the perturbation voltage to obtain the current of the first characteristic point x1, and steps S4 to S6 are executed; finally, step S7 is executed, and power tracking is performed using the P&O algorithm by combining large and small step sizes to obtain the power convergence value.

[0176] Optionally, if LMPP3 and LMPP4 converge to relatively close power values ​​after power point tracking (P&O) using a large-step P&O algorithm, then a small-step P&O algorithm is further executed for both LMPP3 and LMPP4 voltage intervals. That is, within the two voltage intervals, the P&O algorithm's tracking results converge to a single point, resulting in two converged values. As an example, a power difference threshold can be set to determine whether further P&O algorithm execution is needed for LMPP points with smaller approximate maximum power.

[0177] S8: Determine the maximum value among multiple power convergence values ​​as the global maximum power point.

[0178] Therefore, by using the power tracking algorithm to determine the global maximum power point only within the selected interval where the global maximum power point may exist, the convergence speed of the MPPT algorithm can be accelerated, and the algorithm can have a high degree of recognition of the maximum power. Even if the power corresponding to the LMPP point and the power corresponding to the GMPP point are very close, the GMPP point can be correctly identified.

[0179] See Figure 10The figure is a schematic diagram of a maximum power tracking device provided in an embodiment of this application. The device includes: an acquisition module 11, a determination module 12, a calculation module 13, and an output module 14.

[0180] The acquisition module 11 is used to acquire the local maximum power point and the initial maximum power point based on the constraints of the local maximum power point and the photovoltaic system parameters.

[0181] The initial maximum power point is the local maximum power point with the largest power value, and the power value of the initial maximum power point is the initial maximum power value.

[0182] The determination module 12 is used to determine the target maximum power point from the local maximum power point based on the tangent line of the power and voltage characteristic curves at the local maximum power point and the current and voltage characteristic curves.

[0183] The calculation module 13 is used to track the target maximum power point and the target maximum power point respectively within the axis interval of the initial maximum power point and the axis interval of the target maximum power point using the power tracking algorithm, so as to obtain the first convergence value of the target maximum power point and the second convergence value of the initial maximum power point.

[0184] Output module 14 is used to determine the global maximum power point based on the maximum value between the first convergence value and the second convergence value.

[0185] Therefore, the maximum power point provided in this application embodiment can first determine the initial maximum power point, then compare it with other local maximum power points, quickly filter out the intervals where the global maximum power point may exist, and determine the global maximum power point in these intervals through the power point tracking algorithm. Thus, the global search for the maximum power point can be quickly achieved through a simple algorithm, and the multi-peak problem can be better addressed in the process of tracking the maximum power of the photovoltaic system.

[0186] Optionally, the acquisition module 11 is specifically used to: determine all local maximum power points based on the constraints of the local maximum power points and the photovoltaic system parameters; and determine the local maximum power point with the largest power value among all local maximum power points as the initial maximum power point.

[0187] Optionally, the determining module 12 includes a feature point determining unit 121, a slope calculation unit 122, and a target maximum power point determining unit 123; wherein, the feature point determining unit 121 is used to determine a first feature point in the current and voltage characteristic curve based on the tangent line of the power and voltage characteristic curve at the local maximum power point and the first voltage on the tangent line corresponding to the initial maximum power value; and to determine a second feature point corresponding to the local maximum power point on the current and voltage characteristic curve; the slope calculation unit 122 is used to calculate the slope of the line connecting the first feature point and the second feature point; and the target maximum power point determining unit 123 is used to determine the local maximum power point as the target maximum power point when the absolute value of the slope is less than a preset slope threshold.

[0188] Optionally, in another maximum power tracking device provided in this application embodiment, the device further includes a filtering module, used to remove local maximum power points whose absolute difference is greater than a preset threshold based on the absolute value of the difference between the power value corresponding to each local maximum power point and the initial maximum power value.

[0189] Optionally, in another maximum power point tracking device provided in this application embodiment, the device further includes a restart module, used to redetermine the global maximum power point when the absolute value of the difference between the real-time power and the power corresponding to the global maximum power point is greater than a first difference threshold and the duration is greater than a first duration.

[0190] Optionally, in another maximum power point tracking device provided in this application embodiment, the device further includes a reset module, which is used to compare the current power and the historical power under the same voltage when the number of iterations of the global maximum power point reaches the maximum number of iterations; if the absolute value of the difference between the current power and the historical power is greater than a second difference threshold, then the global maximum power point is re-determined.

[0191] See Figure 11 The figure is a structural diagram of a maximum power point tracking device provided in an embodiment of this application. The device includes a memory 100 and a processor 200.

[0192] Memory 100: Used to store program code and transfer program code to the processor.

[0193] Processor 200: Used to execute the steps of the maximum power tracking method described above according to the instructions in the program code.

[0194] In addition, this application also provides a computer-readable storage medium storing computer instructions that, when executed on a maximum power tracking device, cause the maximum power tracking device to perform the steps of the above-described maximum power tracking method.

[0195] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the device and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiments. The device and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components indicated as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of the solution in this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0196] The above description is merely one specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A maximum power point tracking method for a photovoltaic system, characterized in that, The method includes: Based on the constraints of the local maximum power point of the photovoltaic system and the parameters of the photovoltaic system, the local maximum power point within the voltage range where each peak is located is determined from the power and voltage characteristic curves during the operation of the photovoltaic system; the power and voltage characteristic curves have multiple peaks. Based on the voltage values ​​corresponding to each of the multiple local maximum power points, power tracking is performed using a power tracking algorithm to obtain the power convergence value within the voltage interval of each local maximum power point; the power convergence value represents the maximum power within the voltage interval of the corresponding local maximum power point. The maximum value among the multiple power convergence values ​​is determined as the global maximum power point.

2. The method according to claim 1, characterized in that, Before obtaining the power convergence value within the voltage interval of each of the multiple local maximum power points by performing power tracking using a power tracking algorithm based on the voltage values ​​corresponding to each of the multiple local maximum power points, the method further includes: Based on preset filtering rules and an initial maximum power point, select the local maximum power point that meets the filtering rules from multiple local maximum power points as the target maximum power point; the filtering rules are used to: filter local maximum power points whose power values ​​are close to the power values ​​of the initial maximum power point; the initial maximum power point is the local maximum power point with the largest corresponding power value; The step of power tracking based on the voltage values ​​corresponding to each of the multiple local maximum power points, and obtaining the power convergence value within the voltage interval of each local maximum power point, includes: Based on the voltage value corresponding to the target maximum power point and the voltage value corresponding to the initial maximum power point, power tracking is performed using a power tracking algorithm to obtain the power convergence value within the voltage range where the target maximum power point is located and the power convergence value within the voltage range where the initial maximum power point is located.

3. The method according to claim 2, characterized in that, The step of removing local maximum power points that meet the preset filtering rules from multiple local maximum power points to obtain the target maximum power point includes: Based on the tangents of the power and voltage characteristic curves at each of the local maximum power points, the first voltage corresponding to the initial maximum power value in each tangent is determined; the initial maximum power value is the power value corresponding to the initial maximum power point. By voltage mapping, from the current and voltage characteristic curves, corresponding to each tangent line, the first characteristic point corresponding to the first voltage and the second characteristic point corresponding to the local maximum power point voltage are determined respectively; the voltage ranges of the current and voltage characteristic curves and the power and voltage characteristic curves are the same; Calculate the slope of the line connecting the first feature point and the second feature point; Among the multiple local maximum power points, the local maximum power point whose slope of the line connecting the first feature point and the second feature point is less than a preset slope threshold is selected as the target maximum power point.

4. The method according to claim 2, characterized in that, The step of removing local maximum power points that meet the preset filtering rules from multiple local maximum power points to obtain the target maximum power point includes: Calculate the difference between the initial maximum power value and the power value corresponding to each local maximum power point; the initial maximum power value is the power value corresponding to the initial maximum power point. The local maximum power point corresponding to the difference less than the preset threshold is selected as the target maximum power point.

5. The method according to claim 1, characterized in that, After determining the maximum value among the plurality of power convergence values ​​as the global maximum power point, the method further includes: Calculate the absolute value of the first difference between the real-time power value and the power value corresponding to the global maximum power point; If the absolute value of the first difference is greater than the first difference threshold and the duration is greater than the first duration, then the global maximum power point is redefined.

6. The method according to claim 1, characterized in that, After determining the maximum value among the plurality of power convergence values ​​as the global maximum power point, the method further includes: If the number of iterations of the photovoltaic system operating point based on the global maximum power point reaches the maximum number of iterations, then the absolute value of the second difference between the current power value and the historical power value under the same voltage is calculated. If the absolute value of the second difference is greater than the second difference threshold, then the global maximum power point is redefined.

7. A maximum power point tracking device for a photovoltaic system, characterized in that, The device includes: a determination module, a power tracking module, and an output module; The determining module is used to determine the local maximum power point within the voltage range of each peak from the power and voltage characteristic curves during the operation of the photovoltaic system, based on the constraints of the local maximum power point of the photovoltaic system and the parameters of the photovoltaic system; the power and voltage characteristic curves have multiple peaks. The power tracking module is used to perform power tracking based on the voltage values ​​corresponding to each of the multiple local maximum power points using a power tracking algorithm, and to obtain the power convergence value within the voltage interval of each local maximum power point; the power convergence value represents the maximum power within the voltage interval of the corresponding local maximum power point. The output module is used to determine the maximum value among the plurality of power convergence values ​​as the global maximum power point.

8. The apparatus according to claim 7, characterized in that, The device further includes: a screening module; The filtering module is used to select, based on preset filtering rules and an initial maximum power point, a local maximum power point that meets the filtering rules from among multiple local maximum power points as a target maximum power point; the filtering rules are used to: filter local maximum power points whose power values ​​are close to the power values ​​of the initial maximum power point; the initial maximum power point is the local maximum power point with the largest corresponding power value; The power tracking module is specifically used to perform power tracking using a power tracking algorithm based on the voltage value corresponding to the target maximum power point and the voltage value corresponding to the initial maximum power point, respectively, to obtain the power convergence value within the voltage interval where the target maximum power point is located and the power convergence value within the voltage interval where the initial maximum power point is located.

9. A maximum power point tracking device for a photovoltaic system, characterized in that, The device includes: a memory and a processor; The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the steps of the maximum power point tracking method for the photovoltaic system according to any one of claims 1-6, based on the program code.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when run on the maximum power tracking device of the photovoltaic system, executes the steps of the maximum power tracking method of the photovoltaic system as described in any one of claims 1-6.

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