Maximum power point tracking control method and device based on improved perturb and observe method

Abstract

This invention belongs to the field of new energy power generation technology, specifically relating to a maximum power point tracking control method and device based on an improved disturbance observation method. The method first obtains the average input current I of the photovoltaic inverter. inavg Input power P in Output power P out and input-side power increment ΔP in Then I inavg <I max P out <P max And if the maximum power point is not at the knee position: if ΔP in <-P in Then the control increases the disturbance step size by one step size U1; if ΔP in ≥-P in Then the control reduces the disturbance step size by a second step size U2; where I max P represents the peak current. max U2 represents peak power, and U1 > U2. This invention accurately determines the operating state of the photovoltaic inverter and then searches for the appropriate step size. Different step sizes are selected for different situations to achieve maximum power point tracking, ensuring the tracking speed of the maximum power point, providing superior tracking capability, and improving the overall stability and reliability of the system.

Description

Technical Field

[0001] This invention belongs to the field of new energy power generation technology, specifically relating to a maximum power point tracking control method and device based on an improved disturbance observation method. Background Technology

[0002] With the advent of carbon peaking and carbon neutrality, photovoltaic power generation has demonstrated enormous application potential due to its clean, environmentally friendly, and efficient advantages. However, changes in external environmental conditions can cause significant nonlinearity in the voltage and current output of photovoltaic arrays. Therefore, the use of Maximum Power Point Tracking (MPPT) technology in photovoltaic arrays is essential. Domestic and international scholars have proposed numerous MPPT algorithms, which can be categorized into three types. The first type consists of general rule-based algorithms, including constant voltage tracking and short-circuit current tracking. These algorithms apply simple rule calculations to the characteristics exhibited by the photovoltaic array, offering fast tracking speeds and simple control, but their accuracy and stability need improvement. Furthermore, measuring the short-circuit current is difficult in the short-circuit current tracking method. The second type comprises more recently proposed adaptive control algorithms, including those based on fuzzy theory, artificial neural networks, particle swarm optimization, and genetic algorithms. While these algorithms improve tracking accuracy, their complexity leads to longer system runtimes, slower MPPT speeds, and increased hardware costs. The third category of algorithms is the self-optimizing algorithm, mainly including the perturbation and observe (P&Q) method and the incremental conductance (INC) method. Both algorithms determine the direction of voltage perturbation by judging the continuous change trend of power. Near the maximum power point, a small perturbation step size is applied; further away from the maximum power point, a larger perturbation step size is applied to quickly reach the maximum power point of the photovoltaic system. The incremental conductance method has good control effect and high stability, and the photovoltaic array can stably follow changes in the external environment. However, its algorithm is relatively complex, resulting in longer tracking time and higher hardware requirements, so it is not commonly used. The perturbation and observe method is simple and has a fast tracking speed, but its stability is not as good as the incremental conductance method. Most existing technologies use the perturbation and observe method based on inverter input parameters, which involves a single parameter and a fixed step size, making it prone to system oscillations and misjudgments. Summary of the Invention

[0003] The purpose of this invention is to provide a maximum power point tracking control method and apparatus based on an improved perturbation-observation method, in order to solve the problems of system oscillation and misjudgment caused by using the perturbation-observation method in the prior art for maximum power point tracking.

[0004] To address the aforementioned technical problems, this invention provides a maximum power point tracking control method based on an improved perturbation-observation method, which obtains the average input current I of the photovoltaic inverter. inavg Input power P in Output power P out and input-side power increment ΔP in ; in I inavg <I max P out <P max And if the maximum power point is not at the knee position: if ΔP in <-P in Then the control increases the disturbance step size by one step size U1; if ΔP in ≥-P in Then the control reduces the disturbance step size by a second step size U2; where I max P represents the peak current. max U2 represents peak power, and U1 > U2.

[0005] Its beneficial effects are as follows: This invention is based on the disturbance observation method, and determines the direction of disturbance through multiple parameters, including the average current I on the input side. inavg Output power P out Input-side power increment ΔP in The magnitude of the value and the location of the maximum power point (MPP) are used to accurately determine the operating state of the photovoltaic inverter, and then to determine and search the step size. Different step sizes are selected for different situations to achieve MPP tracking, thereby improving the output efficiency of the photovoltaic array, ensuring the tracking speed of the MPP, and exhibiting superior tracking capability. Furthermore, it reduces the oscillation of the photovoltaic system at the MPP, keeping the inverter operating in a stable state and improving the overall stability and reliability of the system. Specifically, in I... inavg <I max P out <P max The maximum power point is not at the knee position, and ΔP in <-P in In the case of a situation where the shadow is continuously occluded, the point is located to the left of the maximum power point. Therefore, only a minimum step size U1 needs to be added. Conversely, a relatively larger step size U1 should be subtracted to achieve the goal of quickly tracking the maximum power point.

[0006] Furthermore, in I inavg ≥I maxIn the case of [condition], the control increases the disturbance step size by the first step size U1.

[0007] Its beneficial effects are: In I inavg ≥I max In this case, it means that the point is at or near the maximum power point. Simply adding a minimum step size U1 will achieve the goal of quickly tracking the maximum power point.

[0008] Furthermore, in I inavg <I max P out <P max The maximum power point is at the knee position, ΔP out <-P out And ΔP in When ΔP > 0: If the number of times the step size is reduced is greater than the set number, the control will reduce the disturbance step size by a fourth step U4; otherwise, the control will reduce the disturbance step size by a third step U3; where ΔP out This indicates the power increment on the output side, U4 > U2 > U3 > U1.

[0009] Its beneficial effect is as follows: The above situation indicates a state of shadow occlusion followed by recovery, ΔP in >0, at this time it is located to the right of the maximum power point, and if the number of steps to decrease is greater than the set number but the maximum power point has not been reached, then the maximum step size U4 is continued to be subtracted. If the number of steps to decrease is less than the set number and the maximum power point has been reached, then the relatively smaller step size U3 is continued to be subtracted in order to achieve the purpose of quickly tracking the maximum power point.

[0010] Furthermore, in I inavg <I max P out <P max The maximum power point is at the knee position, ΔP out <-P out And ΔP in When ≤0: If the number of times the step size increases is greater than or equal to the set number, the control increases the disturbance step size by a fourth step size U4; otherwise, the control increases the disturbance step size by a first step size U1; where ΔP out This indicates the power increment on the output side, where U4 > U2.

[0011] Its beneficial effect is: the situation described indicates a state of being occluded in shadow and then recovering, ΔP in When the step size is ≤0, if the current step size has increased by more than or equal to the set number of times but the maximum power point has not yet been reached, the perturbation in the positive direction continues and the maximum step size U4 is added. If the current step size has increased by less than the set number of times and the maximum power point has been reached, the minimum step size U1 is added, thereby achieving the purpose of quickly tracking the maximum power point.

[0012] Furthermore, in I inavg <I max P out <P max The maximum power point is at the knee position, ΔP out ≥-P out ΔP out >P out And ΔP in When ΔP > 0: If the number of times the step size increases is greater than or equal to the set number, the control increases the disturbance step size by a fourth step U4; otherwise, the control increases the disturbance step size by a third step U3; where ΔP out This indicates the power increment on the output side, U4 > U2 > U3 > U1.

[0013] Its beneficial effect is that the above situation belongs to the stage where power is constantly increasing, if ΔP out >P out And ΔP in If the current step size increment is greater than or equal to the set number of times, and it is determined that the maximum power point is still far away, then continue the positive perturbation and increase the step size by a larger value U4. If the current step size increment is less than the set number of times, and it is determined that the maximum power point is near, then increase the step size by a relatively smaller step size U3 to achieve the purpose of quickly tracking the maximum power point.

[0014] Furthermore, in I inavg <I max P out <P max The maximum power point is at the knee position, ΔP out ≥-P out ΔP out >P out And ΔP in When ≤0: If the number of times the step size increases is greater than or equal to the set number, the control reduces the disturbance step size by a fourth step U4; otherwise, the control reduces the disturbance step size by a third step U3; where ΔP out This indicates the power increment on the output side, U4 > U2 > U3 > U1.

[0015] Its beneficial effect is that the above situation belongs to the stage where power is constantly increasing, if ΔP out >P out And ΔP in If the current step size decreases by more than or equal to the set number of times and it is determined that the current position is still far from the maximum power point, the perturbation continues in the opposite direction, and the step size is reduced by one maximum step size U4. If the current step size decreases by less than the set number of times and it is determined that the current position is near the maximum power point, the step size is reduced by a relatively smaller step size U3 to achieve the purpose of quickly tracking the maximum power point.

[0016] Furthermore, if Iinavg <I max P out <P max The maximum power point is at the knee position, ΔP out ≥-P out And ΔP out ≤P out In this case, both the number of times the step size increases and decreases are set to 0, thus affecting ΔP. in When ΔP > 0: out If ΔP > 0, the control increases the disturbance step size by one step size U1; otherwise, the control decreases the disturbance step size by one step size U1; where ΔP out This indicates the power increment on the output side.

[0017] Furthermore, after setting both the number of times the step size increases and the number of times the step size decreases to 0, then in ΔP in In the case where ≤0: if ΔP out If the value is greater than 0, the control will decrease the disturbance step size by the first step size U1; otherwise, the control will increase the disturbance step size by the first step size U1.

[0018] Furthermore, by collecting the input voltage U of the photovoltaic inverter in Input side current I in Output voltage U out and output current I out The average current I on the input side is calculated. inavg Input power P in Output power P out and input-side power increment ΔP in .

[0019] Its beneficial effects are: utilizing the input voltage U of the photovoltaic inverter in Input side current I in Output voltage U out and output current I out The average input current I can be calculated simply and quickly. inavg Input power P in Output power P out and input-side power increment ΔP in .

[0020] To address the aforementioned technical problems, the present invention also provides a maximum power point tracking control device based on an improved perturbation-observation method, comprising a memory and a processor. The processor is used to execute computer program instructions stored in the memory to implement the maximum power point tracking control method based on the improved perturbation-observation method described above, and to achieve the same beneficial effects as the method. Attached Figure Description

[0021] Figure 1 This is a flowchart of the maximum power point tracking control method based on the improved disturbance observation method of the present invention;

[0022] Figure 2-1 This is a graph showing the IU characteristic curve of a photovoltaic cell;

[0023] Figure 2-2 This is a graph showing the PU characteristics of a photovoltaic cell.

[0024] Figure 2-3 This is a graph showing the IU characteristic curve of a photovoltaic cell under shaded conditions.

[0025] Figure 2-4 This is a graph showing the PU characteristics of a photovoltaic cell under shaded conditions.

[0026] Figure 3 This is a comparison chart of simulation results between traditional maximum power point tracking and the improved maximum power point tracking method of this invention.

[0027] Figure 4 yes Figure 3 A magnified view of a portion of the image. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0029] Method Implementation Examples:

[0030] The flowchart of the maximum power point tracking control method based on the improved disturbance observation method of the present invention is as follows: Figure 1 As shown, four step sizes are set: the first step size U1, the second step size U2, the third step size U3, and the fourth step size U4. The order of these four step sizes is U4 > U2 > U3 > U1.

[0031] During the power generation process in a photovoltaic inverter, if the photovoltaic modules are operating normally without being shaded, the knee point is the maximum power point. This maximum power point is unique and has only one value. Figure 2-1 and Figure 2-2 As shown. If occlusion exists, there will be multiple knee points, but only one maximum power point, such as... Figure 2-3 and Figure 2-4 As shown, the second black dot from the left is the point of maximum power. Therefore, a comprehensive judgment is made considering multiple scenarios. The specific process is as follows:

[0032] Step 1: First, collect the input voltage U of the photovoltaic inverter. in Input side current I in Output voltage U out and output side current Iout And calculate the average input current I. inavg Input power P in and output power P out .

[0033] Step 2: Calculate the average input current I from Step 1. inavg With peak current I max Comparison: If the average input current I obtained at this moment inavg Greater than or equal to peak current I max At this moment, if the perturbation step direction is positive, the step size is increased by U1; otherwise, proceed to step 3. After completing one cycle of calculation, the program continuously calculates the average current I. inavg and peak current I max It will calculate the average value of each time period within the cycle and the peak current I. max By making a comparison, we find that the current is the current maximum point. This means that we are at or near the maximum power point. We only need to add a minimum step size U1.

[0034] Step 3: Calculate the output power P obtained in Step 1. out With peak power P max Comparison: If the output power P obtained at this moment out Greater than or equal to peak power P max And the output power P out Less than 0.95 times the rated power P N At this moment, it is located at knee point P. knee The position is to the right of the maximum power point; conversely, if the output power P obtained at this moment... out Less than peak power P max Proceed to Step 4. max and I max The values ​​are not constant; they are all maximum values ​​relative to a given period. For example, if it is at 50% P... N When running, the inverter's Pmax is 50% of P. N Nearby, if it is at 80% P N When running, the inverter's Pmax is 80% of P. N Nearby, etc. After obtaining P knee =1 or P knee The problem ends immediately after determining that P = 0, because the program runs in a loop. Let's assume that in this round... knee The process ended when P was set to 1. This should happen again in the next iteration of the program. knee =1, after judging I inavg ≥I max Pout ≥P max If the condition is not met, proceed directly to the judgment P. knee =1, continue with the next judgment.

[0035] Step 4: If the current maximum power point is at knee point P knee If the position is correct, proceed to Step 5; otherwise, compare the input-side power increment ΔP. in With negative input-side power value -P in The relationship between their magnitudes: If ΔP in <-P in If the perturbation direction is positive, the step size is increased by U1; otherwise, if the perturbation step size is negative, the step size is decreased by U2. This stage refers to the situation where shadow occlusion is continuous, as described above. Figure 2-3 and Figure 2-4 As shown, under shadow occlusion, the point of maximum power changes from the second black dot from the left to the third black dot, at which point ΔP exists. in <-P in In this case, the maximum power point is the third black dot, located to the left of the maximum power point, so the step size is increased by U1; otherwise, the perturbation step size is decreased by U2.

[0036] Step 5: If the current output power increment ΔP out Less than negative output power -P out Then compare the current input-side power increment ΔP in Size: in ΔP in When ΔP > 0, if the current step size reduction count is greater than or equal to 4, then perform a perturbation in the opposite direction, reducing the step size by U4; if the current step size reduction count is less than 4, then reduce the step size by U3; at the current ΔP in When the value is ≤0, if the current step size has increased by 4 times or more, then a positive perturbation is applied, increasing the step size by U4; if the current step size has increased by less than 4 times, then the step size is increased by U1. If the current output power increment ΔP... out Output power greater than or equal to negative -P out Then proceed to Step 6. This stage involves a situation where shadow occlusion is followed by restoration, as described above. Figure 2-3 and Figure 2-4 As shown in the figure, in the case where the second black dot from the left becomes the third black dot and then becomes the second black dot again, there exists ΔP. out <-P out In this case, however, the input power ΔP in If the value is >0, the system is currently located to the right of the maximum power point. If the system has decreased the step size by 4 or more steps and has not yet reached the maximum power point, then the system continues to subtract the largest disturbance step size U4. If the system has decreased the step size by less than 4 steps and has reached the vicinity of the maximum power point, then the system subtracts the smaller step size U3. At the current ΔP... inWhen the value is ≤0, if the current step size has increased by 4 times or more and the maximum power point has not yet been reached, continue the perturbation in the positive direction and increase the maximum step size U4. If the current step size has increased by less than 4 times and the maximum power point has been reached, increase the minimum step size U1. If the current output power increment ΔP out Output power greater than or equal to negative -P out Then proceed to Step 6.

[0037] Step 6: If the current output power increment ΔP out Greater than the output power P out Then compare the current input-side power increment ΔP in Size: in ΔP in When the value is greater than 0, if the current step size has increased by 4 times or more, continue the perturbation in the positive direction and increase the step size by U4; if the current step size has increased by less than 4 times, increase the step size by U3; at the current ΔP in When the value is ≤0, if the current step size has decreased by 4 times or more, continue the perturbation in the opposite direction and decrease the step size by U4. If the current step size has decreased by less than 4 times, decrease the step size by U3. If the current output power increment ΔP out Less than or equal to the output power P out Then proceed to Step 7. This stage is characterized by continuously increasing power; if the current output power increment ΔP... out Greater than the output power P out Then compare the current input-side power increment ΔP in Size: in ΔP in When the step size is greater than or equal to 0, if the current step size has increased by 4 times and the current position is still far from the maximum power point, then continue the positive perturbation and increase the step size by U4. If the current step size has increased by less than 4 times and the current position is near the maximum power point, then increase the step size by U3. in When the value is ≤0, if the current step size has decreased by 4 or more times and the current position is still far from the maximum power point, continue the perturbation in the opposite direction and decrease the step size by U4. If the current step size has decreased by less than 4 times and the current position is near the maximum power point, decrease the step size by U3. If the current output power increment ΔP out Less than or equal to the output power P out Then proceed to Step 7.

[0038] Step 7: If none of the above steps are satisfied, set both the number of times the step size is increased and decreased to 0, and then determine the input-side power increment ΔP. in Value of ΔP: in >0 and the output power increment ΔP out If ΔP is greater than 0, the perturbation is in the positive direction, and the step size is increased by U1; otherwise, the perturbation is in the opposite direction, and the step size is decreased by U1. in≤0 and the power increment ΔP on the output side out If the value is greater than 0, then the perturbation is in the opposite direction, and the step size is decreased by U1; otherwise, the perturbation is in the positive direction, and the step size is increased by U1. (This stage belongs to the single maximum power point judgment, such as...) Figure 2-1 and Figure 2-2 As shown, there is no shadow occlusion.

[0039] Simulation experiments were conducted based on the above method, and the simulation results are as follows: Figure 3 and Figure 4 As shown in the figure, the method of the present invention has a good tracking effect, with small fluctuations at the maximum power point, effectively improving the utilization rate of photovoltaic power generation. It also has better applicability to changes in light radiation intensity and temperature, and can respond quickly to changes caused by environmental influences, better balancing response speed and tracking accuracy.

[0040] Device Example:

[0041] An embodiment of a maximum power point tracking control device based on an improved perturbation-observation method according to the present invention includes a memory, a processor, and an internal bus. The processor and the memory communicate and exchange data with each other through the internal bus. The memory is used to execute computer program instructions stored in the memory to implement the maximum power point tracking control method based on the improved perturbation-observation method described in the method embodiment of the present invention. The processor can be a microprocessor (MCU), a programmable logic device (FPGA), or other processing device; the memory can be various types of memory that store information using electrical energy, such as RAM or ROM.

Claims

1. A maximum power point tracking control method based on an improved disturbance observation method, characterized in that, include: Obtain the average input current I of the photovoltaic inverter inavg Input power P in Output power P out and input-side power increment ΔP in ; in I inavg <I max P out <P max And if the maximum power point is not at the knee position: if ΔP in <-P in Then the control increases the disturbance step size by one step size U1; if ΔP in ≥-P in Then the control reduces the disturbance step size by a second step size U2; where I max P represents the peak current. max U2 represents peak power, and U1 > U2. If I inavg <I max P out <P max The maximum power point is at the knee position, ΔP out ≥-P out And ΔP out ≤P out In this case, both the number of times the step size increases and decreases are set to 0, and thus: In ΔP in When ΔP > 0: out If ΔP > 0, the control increases the disturbance step size by one step size U1; otherwise, the control decreases the disturbance step size by one step size U1; where ΔP out Indicates the output power increment; In ΔP in In the case where ≤0: if ΔP out If the value is greater than 0, the control will decrease the disturbance step size by the first step size U1; otherwise, the control will increase the disturbance step size by the first step size U1.

2. The maximum power point tracking control method based on the improved disturbance observation method according to claim 1, characterized in that, in I inavg ≥I max In the case of [condition], the control increases the disturbance step size by the first step size U1.

3. The maximum power point tracking control method based on the improved disturbance observation method according to claim 1, characterized in that, in I inavg <I max P out <P max The maximum power point is at the knee position, ΔP out <-P out And ΔP in When ΔP > 0: If the number of times the step size is reduced is greater than the set number, the control will reduce the disturbance step size by a fourth step U4; otherwise, the control will reduce the disturbance step size by a third step U3; where ΔP out This indicates the power increment on the output side, U4 > U2 > U3 > U1.

4. The maximum power point tracking control method based on the improved disturbance observation method according to claim 1, characterized in that, in I inavg <I max P out <P max The maximum power point is at the knee position, ΔP out <-P out And ΔP in When ≤0: If the number of times the step size increases is greater than or equal to the set number, the control increases the disturbance step size by a fourth step size U4; otherwise, the control increases the disturbance step size by a first step size U1; where ΔP out This indicates the power increment on the output side, where U4 > U2.

5. The maximum power point tracking control method based on the improved disturbance observation method according to claim 1, characterized in that, in I inavg <I max P out <P max The maximum power point is at the knee position, ΔP out ≥-P out ΔP out >P out And ΔP in When ΔP > 0: If the number of times the step size increases is greater than or equal to the set number, the control increases the disturbance step size by a fourth step U4; otherwise, the control increases the disturbance step size by a third step U3; where ΔP out This indicates the power increment on the output side, U4 > U2 > U3 > U1.

6. The maximum power point tracking control method based on the improved disturbance observation method according to claim 1, characterized in that, in I inavg <I max P out <P max The maximum power point is at the knee position, ΔP out ≥-P out ΔP out >P out And ΔP in When ≤0: If the number of times the step size increases is greater than or equal to the set number, the control reduces the disturbance step size by a fourth step U4; otherwise, the control reduces the disturbance step size by a third step U3; where ΔP out This indicates the power increment on the output side, U4 > U2 > U3 > U1.

7. The maximum power point tracking control method based on the improved disturbance observation method according to any one of claims 1 to 6, characterized in that, The input voltage U of the photovoltaic inverter was collected. in Input side current I in Output voltage U out and output current I out The average current I on the input side is calculated. inavg Input power P in Output power P out and input-side power increment ΔP in .

8. A maximum power point tracking control device based on an improved perturbation observation method, characterized in that, It includes a memory and a processor, the processor being configured to execute computer program instructions stored in the memory to implement the maximum power point tracking control method based on the improved perturbation observation method as described in any one of claims 1 to 7.

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