Photovoltaic maximum power tracking method and device and computer readable storage medium

Abstract

The application discloses a photovoltaic maximum power tracking method and device, comprising: periodically collecting output voltage and output power of photovoltaic array power generation output; obtaining output voltage and output power of three latest collected working points, and arranging the three working points in order from small to large as working points A, B and C according to the size of output voltage; judging the output power change trend of the three working points, and adjusting the next step output voltage of the photovoltaic array according to the change trend; when the output power Pb of the working point B is the maximum, taking the output voltage Vb of the working point B as a starting point, and approaching the output power of the working point with the larger output power Pa and Pc of the working points A and C in the direction of the output power of the working point with the larger output power by a preset amplitude to be the next step output voltage of the photovoltaic array, and the preset amplitude is smaller than the voltage difference between Vb and the output voltage of the working point with the larger output power Pa and Pc. Compared with the prior art, the application has higher maximum power tracking speed and accuracy.

Description

Technical Field

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

[0002] In actual use, the lighting conditions of photovoltaic power generation systems are not ideal. For example, in cloudy weather, there will be repeated changes in illuminance, and the operating points of the voltage and current for maximum power output will also change accordingly. The controller needs to continuously adjust the parameters to improve the maximum power tracking speed and accuracy of the photovoltaic power generation system.

[0003] Common maximum power point tracking (MPPT) algorithms mainly include the perturbation and observation method (P&O) and the incremental conductance method. The perturbation and observation method, also known as the hill-climbing method, perturbs the output voltage of the photovoltaic (PV) array and calculates the output power before and after the perturbation using P=UI. The comparison of the two output power values ​​determines the direction of voltage approximation. The incremental conductance method modifies the control signal by comparing the incremental conductance of the PV array with its instantaneous conductance.

[0004] The perturbation-observation method for tracking the maximum power point requires continuous voltage perturbation. The step size of the voltage change is determined by the power difference detected during the perturbation. Voltage and current detection and calculation are sensitive to noise and errors, and the step size parameter is difficult to tune and optimize, which can easily lead to operating point oscillation.

[0005] In theory, the incremental conductance method can stabilize the voltage operating point at the maximum power point, reducing oscillations compared to the P&O method. However, in practical applications, when illumination and temperature conditions vary significantly, and due to detection errors and the use of discrete calculation formulas, the incremental conductance method struggles to optimize both tracking accuracy and speed.

[0006] Therefore, how to improve the accuracy and speed of maximum power point tracking in photovoltaic power generation is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a photovoltaic maximum power point tracking method, apparatus, and computer-readable storage medium, which have high maximum power point tracking speed and accuracy.

[0008] To achieve the above objectives, this invention discloses a photovoltaic maximum power point tracking method, comprising: periodically acquiring the output voltage and output power of a photovoltaic array; obtaining the output voltage and output power of the three most recently acquired operating points, and arranging the three operating points in ascending order of output voltage as operating point A, operating point B, and operating point C, where the output voltage of operating point A is Va and the output power is Pa, the output voltage of operating point B is Vb and the output power is Pb, and the output voltage of operating point C is Vc and the output power is Pc; determining the changing trend of the output power Pa, Pb, and Pc from operating point A to operating point B and then to operating point C, and adjusting the output voltage of the photovoltaic array for the next step accordingly based on the changing trend of Pa, Pb, and Pc, wherein when Pb is the largest among Pa, Pb, and Pc, comparing the magnitudes of Pa and Pc, and using Vb as a starting point to approach the output power of the operating point with the larger of Pa and Pc by a preset amplitude as the next output voltage of the photovoltaic array, wherein the preset amplitude is less than the voltage difference between Vb and the output voltage of the operating point with the larger of Pa and Pc.

[0009] Preferably, when the power of Pa and Pc is less than or equal to Pb, and Pa is greater than Pc, the output voltage of the photovoltaic array in the next step is controlled to be Vb-V1x; when the power of Pa and Pc is less than or equal to Pb, and Pa is less than Pc, the output voltage of the photovoltaic array in the next step is controlled to be Vb+V2x; V1x is a voltage value taken from the interval (0, Vb-Va), and V2x is a voltage value taken from the interval (0, Vc-Vb).

[0010] Specifically, V1x = M1 × (Vb - Va) and V2x = M2 × (Vc - Vb), where M1 and M2 are both preset percentages greater than 0% and less than 100%.

[0011] More specifically, M1=50%, M2=50%.

[0012] Preferably, the preset amplitude is a preset proportion of the voltage difference between the output voltages at the larger of Vb and Pa and Pc operating points, and this preset proportion is greater than 0% and less than 100%.

[0013] Preferably, when Pb is the largest among Pa, Pb, and Pc, and Pa = Pc, the output power approaches a preset amplitude from Vb as the starting point in the direction of the output power of any one of Pa and Pc.

[0014] Preferably, when the power of Pa, Pb, and Pc increases sequentially, the next output voltage of the photovoltaic array is controlled to be Vc + Vx; when the power of Pa, Pb, and Pc decreases sequentially, the next output voltage of the photovoltaic array is controlled to be Va - Vx. Vx is the basic voltage step size for maximum power point tracking control.

[0015] Preferably, when the power of Pa and Pc is greater than or equal to Pb, and Pa is greater than Pc, the next output voltage of the photovoltaic array is controlled to be Va-Vx; when the power of Pa and Pc is greater than or equal to Pb, and Pa is less than Pc, the next output voltage of the photovoltaic array is controlled to be Vc+Vx. Vx is the basic voltage step size for maximum power point tracking control. This invention also considers situations where the curve is at a low point due to non-ideal conditions caused by external forces, allowing for timely adjustment of the output voltage to ensure the output power reaches the maximum power point.

[0016] Specifically, Vx is a value set between 0.1% and 10% of the open-circuit voltage of the photovoltaic array, and Vx is greater than the first preset limit value and less than the second preset limit value.

[0017] More preferably, if the Pa, Pb, and Pc powers of the changing trend increase or decrease sequentially in two consecutive cycles, the magnitude of Vx is increased to further improve the maximum power tracking speed.

[0018] More preferably, if the trend of change in two consecutive cycles changes from Pb being the largest among Pa, Pb, and Pc to Pa, Pb, and Pc power increasing or decreasing sequentially, then the magnitude of Vx is reduced, and the new basic voltage step size is obtained by reducing the value of Vx to reduce voltage operating point oscillation.

[0019] Specifically, if the power of Pa, Pb, and Pc increases or decreases sequentially in two consecutive cycles, then the value of Vx is doubled.

[0020] The present invention also discloses a photovoltaic maximum power point tracking device, comprising: a signal acquisition circuit for acquiring the output voltage and output power of a photovoltaic array; one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs comprising instructions for performing the photovoltaic maximum power point tracking method as described above.

[0021] The present invention also discloses a computer-readable storage medium comprising a computer program for use in conjunction with an electronic device having a memory, characterized in that the computer program can be executed by a processor using the photovoltaic maximum power point tracking method as described above.

[0022] Compared with existing technologies, this invention directly and periodically collects the output voltage and output power of the photovoltaic array. By collecting the output voltage and output power three times closest to the current moment, three operating points are obtained. The changing trend from operating point A to operating point B and then to operating point C is determined. Based on the changing trends of Pa, Pb, and Pc, the output voltage of the photovoltaic array is adjusted accordingly for the next step. That is, the output voltage corresponding to the operating point with the highest output power among Pa, Pb, and Pc is taken as the starting point, and the output voltage is adjusted by one step in the direction of the current highest output power. The adjustment speed is fast, a high maximum power tracking speed can be obtained, and the tracking accuracy is high with less interference and less prone to operating point oscillation. On the other hand, when the output voltage-output power curve changes from rising to falling along the operating point ABC (when Pb is the largest among Pa, Pb, and Pc), the present invention does not stop tracking the maximum power point. Instead, it starts from Vb and approaches the output power of the operating point with the larger value between Pa and Pc at a preset amplitude that will not reach Pa and Pc. This is used as the output voltage of the photovoltaic array for the next step to find the maximum power point, so that the final adjusted maximum power point is as close as possible to the actual maximum power point, resulting in high adjustment accuracy. Attached Figure Description

[0023] Figure 1 This is the photovoltaic maximum power tracking diagram under the C1 trend of this invention.

[0024] Figure 2 This is the photovoltaic maximum power tracking diagram under the C2 trend of this invention.

[0025] Figure 3 This is the photovoltaic maximum power tracking diagram under the C3 trend of this invention.

[0026] Figure 4 This is the photovoltaic maximum power tracking diagram under the C4 trend of this invention.

[0027] Figure 5 This is a flowchart of the photovoltaic maximum power point tracking method of the present invention. Detailed Implementation

[0028] To illustrate the technical content, structural features, objectives, and effects of the present invention in detail, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0029] refer to Figure 5 The present invention discloses a photovoltaic maximum power point tracking method, comprising steps S1-S4.

[0030] S1, periodically collect the output voltage and output power of the photovoltaic array. This invention directly collects the output voltage and power at a preset period during photovoltaic array power generation.

[0031] S2, obtain the output voltage and output power of the three most recent acquisition points, and arrange the three working points in ascending order of output voltage as working point A, working point B, and working point C.

[0032] Wherein, the output voltage at operating point A is Va and the output power is Pa, the output voltage at operating point B is Vb and the output power is Pb, and the output voltage at operating point C is Vc and the output power is P. Wherein, Vb - Va = V1, Vc - Vb = V2, and V1 and V2 are non-negative voltage values.

[0033] S3, determine the changing trends of the output power Pa, Pb, and Pc from operating point A to operating point B and then to operating point C.

[0034] In this invention, a two-dimensional coordinate system is established with output voltage as the abscissa and output power as the ordinate. An output voltage-output power relationship curve is formed in the coordinate system. The output voltage-output power relationship curve under the continuous change of voltage from small to large is divided into four changing trends: C1, C2, C3, and C4. The working points A, B, and C of the output voltage and output power collected at the above three different times form three coordinate points A, B, and C in the coordinate system.

[0035] Unlike the relationship curve between photovoltaic power output voltage and output power under ideal conditions, the relationship between photovoltaic power output voltage and power under non-ideal conditions is as follows: Figures 1 to 4 As shown.

[0036] refer to Figure 1 When the power of Pa, Pb, and Pc increases sequentially, the trend is C1.

[0037] refer to Figure 2 When the power of Pa, Pb, and Pc decreases sequentially, the trend is C2.

[0038] refer to Figure 3 When the power of Pa and Pc is less than or equal to that of Pb, the trend is C3.

[0039] refer to Figure 4 When the power of Pa and Pc is greater than or equal to that of Pb, the trend is C4.

[0040] S4. Adjust the output voltage of the photovoltaic array for the next step according to the changing trends of Pa, Pb, and Pc. Starting from the output voltage corresponding to the operating point with the highest output power among Pa, Pb, and Pc, adjust the output voltage by a step size in the direction of the current highest output power. This step size is a specifically set step size.

[0041] refer to Figure 1In step S4, under the trend of C1, as the power of Pa, Pb, and Pc increases sequentially, the output voltage of the photovoltaic array in the next step is controlled to be Vc + Vx. Vx is the basic voltage step size for maximum power point tracking control. The basic voltage step size is a value preset by the system and can have an initial value. In this embodiment, Vx is a value set with the open-circuit voltage of the photovoltaic array as a reference. Specifically, Vx is a value set between 0.1% and 10% of the open-circuit voltage of the photovoltaic array, and Vx is greater than the first preset limit value and less than the second preset limit value. More preferably, if the power of Pa, Pb, and Pc increases sequentially in two consecutive cycles, the magnitude of Vx is increased. In this embodiment, the value of Vx is doubled. Of course, Vx can also be adjusted by a certain proportion or a fixed value.

[0042] refer to Figure 2 In step S4, under the C2 trend, when the power of Pa, Pb, and Pc decreases sequentially, the output voltage of the photovoltaic array in the next step is controlled to be Va-Vx. If the power of Pa, Pb, and Pc decreases sequentially in two consecutive cycles, the value of Vx is increased. In this embodiment, the value of Vx is doubled. Of course, Vx can also be adjusted by a certain proportion or a fixed value.

[0043] If the trend of the working point changes from C3 to C1 or C2 in two consecutive cycles, then the size of Vx can be reduced. Vx can be reduced according to a preset ratio or a fixed value.

[0044] refer to Figure 3 In step S4, under the C3 trend, Pb is the largest among Pa, Pb, and Pc. At this time, the magnitudes of Pa and Pc are compared, and starting from Vb, the output voltage of the photovoltaic array approaches the output power of the larger of Pa and Pc by a preset amplitude to obtain the next output voltage. The next output voltage is less than the output voltage of the larger of Pa and Pc. When Pa = Pc, the output voltage approaches the preset amplitude starting from Vb in the direction of the output power of either Pa or Pc.

[0045] Specifically, when the power of Pa and Pc is less than or equal to Pb, and Pa is greater than Pc, the next output voltage of the photovoltaic array is controlled to be Vb-V1x. When the power of Pa and Pc is less than or equal to Pb, and Pa is less than Pc, the next output voltage of the photovoltaic array is controlled to be Vb+V2x; V1x is a voltage value taken from the interval (0, V1), and V2x is a voltage value taken from the interval (0, V2).

[0046] Specifically, V1x = M1 × V1, V2x = M2 × V2, where M1 and M2 are both preset percentages greater than 0% and less than 100%. M1 can be equal to M2 or not. More specifically, M1 = 50%, M2 = 50%. Of course, M1 and M2 can also use other values, not limited to 50%. Naturally, M1 and M2 have minimum and maximum limits. That is, this preset amplitude is a preset proportional amplitude, which is a preset proportion of the voltage difference between the output voltage at the larger operating point between Vb and Pa and Pc, and this preset proportion is greater than 0% and less than 100%.

[0047] Ideally, to track the maximum power point more accurately and quickly, under the C3 trend, the first difference between Pa and Pc is also compared. When the first difference is less than a first limit, the corresponding settings of M1 and M2 are decreased; when the first difference is greater than a second limit, the corresponding settings of M1 and M2 are increased. Specifically, different levels of M1 and M2 can be set, selecting the appropriate M1 and M2 based on the range of the first difference; the smaller the first difference, the smaller M1 and M2.

[0048] refer to Figure 4 In step S4, under the C4 trend, when the power of Pa and Pc is greater than or equal to Pb, and Pa is greater than Pc, the output voltage of the photovoltaic array in the next step is controlled to be Va-Vx; when the power of Pa and Pc is greater than or equal to Pb, and Pa is less than Pc, the output voltage of the photovoltaic array in the next step is controlled to be Vc+Vx.

[0049] Among them, when the power of Pa and Pc is greater than or equal to Pb, and Pa=Pc, Vx is approached from either Va or Vc in a direction away from Vb, or Vx is approached from Vc in a direction away from Vb.

[0050] The present invention also discloses a photovoltaic maximum power point tracking device, comprising: a signal acquisition circuit for acquiring the output voltage and output power of a photovoltaic array; one or more processors; a memory; and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, the programs comprising instructions for performing the photovoltaic maximum power point tracking method as described above.

[0051] The present invention also discloses a computer-readable storage medium comprising a computer program for use in conjunction with an electronic device having a memory, characterized in that the computer program can be executed by a processor using the photovoltaic maximum power point tracking method as described above.

[0052] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A photovoltaic maximum power point tracking method, characterized in that: include: Periodically collect the output voltage and output power of the photovoltaic array; Obtain the output voltage and output power of the three most recent acquisition points, and arrange the three working points in ascending order of output voltage as working point A, working point B, and working point C. The output voltage of working point A is Va and the output power is Pa, the output voltage of working point B is Vb and the output power is Pb, and the output voltage of working point C is Vc and the output power is Pc. The changing trends of the output power Pa, Pb, and Pc from operating point A to operating point B and then to operating point C are determined. Based on the changing trends of Pa, Pb, and Pc, the output voltage of the photovoltaic array is adjusted accordingly for the next step. When Pb is the largest among Pa, Pb, and Pc, the magnitudes of Pa and Pc are compared. Starting from Vb, the voltage approaches the operating point with the larger output power of Pa and Pc by a preset amplitude to serve as the output voltage of the photovoltaic array for the next step. The preset amplitude is less than the voltage difference between Vb and the output voltage of the operating point with the larger output power of Pa and Pc. When Pb is the largest among Pa, Pb, and Pc, and the power of Pa and Pc is less than or equal to Pb, and Pa is greater than Pc, the first difference between Pa and Pc is compared. Based on the range of the first difference, the corresponding M1 is selected. The smaller the first difference, the smaller M1 is. M1 is a preset percentage greater than 0% and less than 100%. The output voltage of the photovoltaic array in the next step is controlled to be Vb-V1x, where V1x=M1×(Vb-Va). When Pb is the largest among Pa, Pb, and Pc, and the power of Pa and Pc is less than or equal to Pb, and Pa is less than Pc, the first difference between Pa and Pc is compared. Based on the range of the first difference, the corresponding M2 is selected. The smaller the first difference, the smaller M2. M2 is a preset percentage greater than 0% and less than 100%. The output voltage of the photovoltaic array in the next step is controlled to be Vb + V2x, where V2x = M2 × (Vc - Vb).

2. The photovoltaic maximum power point tracking method as described in claim 1, characterized in that: When the power of Pa and Pc is less than or equal to Pb, and Pa is greater than Pc, the output voltage of the photovoltaic array in the next step is controlled to be Vb-V1x; When the power of Pa and Pc is less than or equal to Pb, and Pa is less than Pc, the output voltage of the photovoltaic array in the next step is controlled to be Vb + V2x. V1x is a voltage value taken from the interval (0, Vb-Va), and V2x is a voltage value taken from the interval (0, Vc-Vb).

3. The photovoltaic maximum power point tracking method as described in claim 1, characterized in that: The preset amplitude is a preset proportion of the voltage difference between the output voltages at the larger of Vb and Pa and Pc operating points, and this preset proportion is greater than 0% and less than 100%.

4. The photovoltaic maximum power point tracking method as described in claim 1, characterized in that: When Pb is the largest among Pa, Pb, and Pc, and Pa = Pc, the output power approaches the preset amplitude from Vb as the starting point in the direction of the output power of any one of Pa and Pc.

5. The photovoltaic maximum power point tracking method as described in claim 1, characterized in that: When the power of Pa and Pc is greater than or equal to Pb, and Pa is greater than Pc, the output voltage of the photovoltaic array in the next step is controlled to be Va-Vx; When the power of Pa and Pc is greater than or equal to Pb, and Pa is less than Pc, the output voltage of the photovoltaic array in the next step is controlled to be Vc+Vx. Vx is the basic voltage step size for maximum power point tracking control.

6. The photovoltaic maximum power point tracking method as described in claim 5, characterized in that: Vx is a value set between 0.1% and 10% of the open-circuit voltage of the photovoltaic array, and Vx is greater than the first preset limit value and less than the second preset limit value.

7. A photovoltaic maximum power point tracking device, characterized in that: include: The signal acquisition circuit collects the output voltage and output power of the photovoltaic array. One or more processors; Memory; as well as One or more programs, wherein the one or more programs are stored in the memory and configured to be executed by one or more processors, the programs including instructions for performing the photovoltaic maximum power point tracking method as described in any one of claims 1-6.

8. A computer-readable storage medium comprising a computer program for use in conjunction with an electronic device having a memory, characterized in that: The computer program can be executed by a processor using the photovoltaic maximum power point tracking method as described in any one of claims 1-6.

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