MPPT circuit power control methods, power conversion devices and power conversion equipment

Abstract

This application provides a power control method, power conversion device, and power conversion equipment for an MPPT circuit, relating to the field of photovoltaic module technology. The MPPT circuit is electrically connected to the photovoltaic module. The power control method includes: when the real-time power point of the MPPT circuit deviates from the power-voltage curve of the photovoltaic module, calculating the minimum distance from the real-time power point to the power-voltage curve based on the real-time power point and the power-voltage curve; determining the target power point corresponding to the minimum distance; and outputting a control signal to the MPPT circuit based on the target power point. This control signal controls the MPPT circuit to operate at the target power point. Consequently, the real-time power point controlling the MPPT circuit moves towards the target power point, thereby controlling the real-time power point of the MPPT circuit to return to the P-V curve.

Description

Technical Field

[0001] This application relates to the field of photovoltaic (PV) module technology, specifically to a power control method, power conversion device, and power conversion equipment for an MPPT circuit. Background Technology

[0002] Because photovoltaic (PV) modules exhibit nonlinear output characteristics and their output capability is significantly affected by external factors such as light intensity and temperature, maintaining PV modules at their maximum power point (MPP) is challenging. During MPPT, the power-voltage (PV) curve and the MPP continuously change as light intensity and temperature fluctuate. This can lead to the tracked power point deviating from the PV curve. Furthermore, fluctuations in the inductor current within the MPPT circuit can also cause the tracked power point to deviate from the PV curve. When the tracked power point deviates from the PV curve, tracking instability and system malfunction can occur, rendering the MPPT algorithm ineffective and making it difficult or even impossible to track the maximum power point. Summary of the Invention

[0003] This application provides a power control method, power conversion device, and power conversion equipment for an MPPT circuit, aiming to solve the problem of how to bring the power point back to the PV curve when the power point deviates from the PV curve.

[0004] The first aspect of this application provides a power control method for an MPPT circuit electrically connected to a photovoltaic module. The method includes: when the real-time power point of the MPPT circuit deviates from the power voltage curve of the photovoltaic module, calculating the minimum distance between the real-time power point and the power voltage curve based on the real-time power point and the power voltage curve; determining the target power point corresponding to the minimum distance; and outputting a control signal to the MPPT circuit based on the target power point, the control signal being used to control the MPPT circuit to operate at the target power point.

[0005] In this embodiment, during the process of tracking the maximum power point of a photovoltaic module using the MPPT algorithm, when the tracked real-time power point deviates from the PV curve, the minimum distance between the real-time power point and the PV curve is first calculated based on the real-time power point and the PV curve. This minimum distance quantifies the degree of deviation of the real-time power point from the PV curve, and the corresponding target power point is determined based on this minimum distance. Then, a control signal is output to the MPPT circuit based on the target power point. This control signal controls the real-time power point of the MPPT circuit to move towards the target power point, thereby controlling the real-time power point of the MPPT circuit to return to the PV curve. This ensures that the MPPT algorithm can continue to execute, thus improving the stability of the tracking.

[0006] In one embodiment, calculating the minimum distance from the real-time power point to the power voltage curve based on the real-time power point and the power voltage curve includes: determining a first reference power point and a second reference power point located on the power voltage curve based on the real-time power point and the power voltage curve. Here, the first power corresponding to the first reference power point is the real-time power of the real-time power point, and the second voltage corresponding to the second reference power point is the real-time voltage of the real-time power point. A triangular space is formed based on the real-time power point, the first reference power point, and the second reference power point. The triangular space is iterated until the difference between the first distance and the second distance is less than a preset threshold, at which point the final triangular space is determined. Here, after each iteration, both the first reference power point and the second reference power point in the triangular space are located on the power voltage curve, the first distance is the distance from the real-time power point to the first reference power point, and the second distance is the distance from the real-time power point to the second reference power point. The minimum distance from the real-time power point to the power voltage curve is determined based on the first reference power point and the second reference power point in the final triangular space.

[0007] In this embodiment, based on the real-time power and real-time voltage of the real-time power point, the corresponding first reference power point and second reference power point are found on the PV curve. Then, based on the triangular space formed by the real-time power point, the first reference power point, and the second reference power point, the first distance from the real-time power point to the first reference power point and the second distance from the real-time power point to the second reference power point are calculated. When the difference between the first distance and the second distance is greater than or equal to a preset threshold, it indicates that the current triangular space is large. In this case, a new first reference power point and a new second reference power point are found on the PV curve to form a new triangular space. When the difference between the first distance and the second distance is less than the preset threshold, it indicates that the current triangular space is small. The current triangular space is determined as the final triangular space. Then, based on the first reference power point and the second reference power point in the final triangular space, the minimum distance from the real-time power point to the PV curve is determined, thereby ensuring the reliability of the calculated minimum distance.

[0008] In another implementation, the triangular space is iterated until the difference between the first distance and the second distance is less than a preset threshold, and the final triangular space is determined. This includes: determining a temporary reference power point located on the power-voltage curve based on the first and second reference power points in the triangular space. The temporary reference power point is located between the first and second reference power points. A first distance, a second distance, and a third distance are obtained, where the third distance is the distance from the real-time power point to the temporary reference power point. The two reference power points corresponding to the two smaller distance values ​​among the first, second, and third distances are used as the new first and second reference power points. The iterated triangular space is determined using the real-time power point, the new first reference power point, and the new second reference power point. The first distance between the real-time power point and the first reference power point in the iterated triangular space, and the second distance between the real-time power point and the second reference power point in the iterated triangular space are calculated. When the difference between the iterated first distance and the iterated second distance is greater than or equal to a preset threshold, the step of determining the temporary reference power point located on the power-voltage curve based on the first and second reference power points in the triangular space is returned. If the difference between the first distance and the second distance after iteration is less than a preset threshold, the triangular space after iteration is taken as the final triangular space.

[0009] In this embodiment, when the difference between the first distance and the second distance is greater than or equal to a preset threshold, a temporary reference power point is found between the first and second reference power points to narrow the range of the triangular space, and a third distance from the real-time power point to the temporary reference power point is calculated. Based on the two smaller distance values ​​among the first, second, and third distances, a new first reference power point and a new second reference power point are determined. Then, based on the triangular space formed by the real-time power point, the new first reference power point, and the new second reference power point, a new first distance from the real-time power point to the new first reference power point and a new second distance from the real-time power point to the new second reference power point are calculated. The difference between the new first distance and the new second distance is compared with the preset threshold again. When the difference between the new first distance and the new second distance is greater than or equal to the preset threshold, it indicates that the range of the current triangular space is still large. In this case, the search continues on the PV curve for a new first reference power point and a new second reference power point to form a new triangular space. When the difference between the new first distance and the new second distance is less than the preset threshold, it indicates that the range of the current triangular space is small, and the current triangular space is determined as the final triangular space. This limits the final triangular space to a smaller range, which helps ensure the reliability of the calculated minimum distance.

[0010] In another implementation, determining a temporary reference power point on the power-voltage curve based on a first and second reference power point in the triangular space includes: averaging the voltage values ​​corresponding to the first and second reference power points in the triangular space to obtain the voltage value corresponding to the temporary reference power point. The power value corresponding to the temporary reference power point is then determined based on the voltage value and the power-voltage curve.

[0011] In this embodiment, the voltage value corresponding to the temporary reference power point is first determined. The voltage value corresponding to the temporary reference power point is the average of the voltage values ​​corresponding to the first reference power point and the second reference power point. Then, the corresponding power value is determined based on the PV curve and the voltage value, thereby finding the temporary reference power point on the PV curve. In some embodiments, the voltage value corresponding to the temporary reference power point can be any value between the voltage values ​​corresponding to the first reference power point and the second reference power point.

[0012] In another implementation, determining a temporary reference power point on the power-voltage curve based on a first and second reference power point in the triangular space includes: averaging the power values ​​corresponding to the two reference power points in the triangular space to obtain the power value corresponding to the temporary reference power point; and determining the voltage value corresponding to the temporary reference power point based on the power value and the power-voltage curve.

[0013] In this embodiment, the power value corresponding to the temporary reference power point is first determined. The power value corresponding to the temporary reference power point is the average of the power values ​​corresponding to the first reference power point and the second reference power point. Then, the corresponding voltage value is determined based on the PV curve and the power value, thereby finding the temporary reference power point on the PV curve. In some embodiments, the power value corresponding to the temporary reference power point can be any value between the power values ​​corresponding to the first reference power point and the second reference power point.

[0014] In another implementation, determining the minimum distance from the real-time power point to the power-voltage curve based on the first and second reference power points in the final triangular space includes: determining the reference power point with the larger power value among the first and second reference power points in the final triangular space; and determining the distance from the real-time power point to the reference power point with the larger power value as the minimum distance.

[0015] In this embodiment, the power value corresponding to the first reference power point in the final triangular space is compared with the power value corresponding to the second reference power point. The reference power point with the larger power value is found, and then the distance from the real-time power point to the reference power point with the larger power value is calculated to determine the minimum distance. The reference power point with the larger power value is the target power point corresponding to the minimum distance.

[0016] In another implementation, outputting a control signal to the MPPT circuit based on the target power point includes: determining the input voltage reference value and inductor current limit value of the MPPT circuit based on the target power point; determining the duty cycle of the control signal for the MPPT circuit based on the input voltage reference value, the inductor current limit value, and a preset loop control model; and outputting the control signal to the MPPT circuit based on the duty cycle.

[0017] In this embodiment, a preset current value is calculated based on the output voltage and output power of the photovoltaic module at the target power point. The output voltage of the photovoltaic module at the target power point is then set as the input voltage reference value of the MPPT circuit, and the preset current value is set as the inductor current limit value. Next, the input voltage reference value and the inductor current limit value are used as parameters of a preset loop control model. Based on the duty cycle of the control signal output by the preset loop control model, a control signal is output to the MPPT circuit. Based on the control signal, the real-time current value in the MPPT circuit continuously increases, and the real-time power point gradually moves towards the target power point. When the real-time current value in the MPPT circuit reaches the inductor current limit value, the real-time power point overlaps with the target power point, and at this point, the real-time power point returns to the PV curve. Since the distance from the real-time power point back to the PV curve is the minimum distance, the tracking delay to the target power point can be reduced, thereby improving tracking efficiency.

[0018] In another implementation, the preset loop control model includes a voltage loop and a current loop, and the adjustment step size of the voltage loop is determined based on the minimum distance.

[0019] In this embodiment, the minimum distance is divided into multiple distance segments, each representing an adjustment step size. Based on the control signal, the real-time power point moves towards the target power point in increments of one adjustment step size until it overlaps with the target power point. This helps reduce situations where the real-time power point exceeds or fails to reach the target power point during tracking due to calculation errors, thereby improving tracking accuracy.

[0020] A second aspect of this application provides a power conversion device electrically connected to an MPPT circuit, which is electrically connected to a photovoltaic module. The power conversion device includes: a minimum distance calculation module, used to calculate the minimum distance from the real-time power point of the MPPT circuit to the power voltage curve of the photovoltaic module when the real-time power point deviates from the power voltage curve of the photovoltaic module; a target power point determination module, used to determine the target power point corresponding to the minimum distance; and a control signal output module, used to output a control signal to the MPPT circuit according to the target power point, the control signal being used to control the MPPT circuit to operate at the target power point.

[0021] A third aspect of this application provides a power conversion device, which includes an MPPT circuit, a memory, and a controller. The MPPT circuit is used to be electrically connected to a photovoltaic module, the memory is used to store instructions, and the controller is used to run the instructions stored in the memory, so that the power conversion device executes the power control method of the MPPT circuit of this application.

[0022] A fourth aspect of this application provides a computer-readable storage medium for storing instructions that, when executed by a computer, cause the computer to perform the power control method of the MPPT circuit of this application. Attached Figure Description

[0023] Figure 1 This is a block diagram of a power conversion system provided as an example.

[0024] Figure 2 This is a circuit schematic of an MPPT circuit provided as an example.

[0025] Figure 3 This is a schematic diagram of a power-voltage curve provided as an example.

[0026] Figure 4 This is a flowchart of a power control method for an MPPT circuit provided in one embodiment of this application.

[0027] Figure 5 yes Figure 4 Flowchart of the sub-steps in step S401.

[0028] Figure 6 yes Figure 5 Flowchart of the sub-steps in step S503.

[0029] Figure 7 yes Figure 4 Flowchart of the sub-steps in step S403.

[0030] Figure 8 This is a schematic diagram of the structure of a preset loop control model provided as an example.

[0031] Figure 9 This is a structural block diagram of a power conversion device provided in one embodiment of this application.

[0032] Figure 10 This is a structural block diagram of a power conversion device provided in one embodiment of this application. Detailed Implementation

[0033] It should be noted that the terms "first" and "second" in the specification, claims and drawings of this application are used to distinguish similar objects, rather than to describe a specific order or sequence.

[0034] It should also be noted that the methods disclosed in the embodiments of this application or the methods shown in the flowcharts include one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchanged, and some steps can also be deleted.

[0035] Some embodiments will now be described with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0036] Figure 1 This is a block diagram of a power conversion system provided as an example.

[0037] like Figure 1 As shown, the power conversion system 10 includes a photovoltaic module 100, a power conversion device 200, and a load 300. The power conversion device 200 is electrically connected to the photovoltaic module 100 and the load 300. The power conversion device 200 is used to convert the output voltage of the photovoltaic module 100 into a voltage suitable for the load 300, for example, to increase or decrease the output voltage of the photovoltaic module 100 to a voltage range within which the load 300 can operate normally.

[0038] The power conversion device 200 includes an MPPT circuit 210 and a controller 220, with the controller 220 electrically connected to the MPPT circuit 210. The MPPT circuit 210 performs maximum power point tracking (MPPT) on the output voltage of the photovoltaic module 100 based on the control signal output by the controller 220, aiming to maintain the photovoltaic module 100 operating at its maximum power point. The controller 220 generates a control signal based on the input voltage (i.e., the output voltage of the photovoltaic module 100) and output voltage of the MPPT circuit 210, as well as the MPPT algorithm. The specific MPPT algorithm is not limited here.

[0039] For example, such as Figure 2 As shown, the MPPT circuit 210 includes a first bridge arm 211, a second bridge arm 212, and an inductor 213. The first bridge arm 211 includes a first upper switch Q1 and a first lower switch Q2, which are connected in series between the positive input terminal IN+ and the negative input terminal IN-. The second bridge arm 212 includes a second upper switch Q3 and a second lower switch Q4, which are connected in series between the positive output terminal OUT+ and the negative output terminal OUT-. The inductor 213 is electrically connected between the midpoint of the first bridge arm 211 and the midpoint of the second bridge arm 212, forming an H-bridge between the first bridge arm 211 and the second bridge arm 212. That is, one end of the inductor 213 is electrically connected between the first upper switch Q1 and the first lower switch Q2, and the other end of the inductor 213 is electrically connected between the second upper switch Q3 and the second lower switch Q4.

[0040] The first upper switch Q1, the first lower switch Q2, the second upper switch Q3, and the second lower switch Q4 are turned on or off based on control signals, enabling the MPPT circuit 210 to operate in either Buck or Boost mode. For example, in the first time period, with the second upper switch Q3 on and the second lower switch Q4 off, the first upper switch Q1 and the first lower switch Q2 are complementaryly turned on, with the timing of this complementary turn-on determined by the control signal for the first time period, thus enabling the MPPT circuit 210 to operate in Buck mode. In the second time period, with the first upper switch Q1 on and the first lower switch Q2 off, the second upper switch Q3 and the second lower switch Q4 are complementaryly turned on, with the timing of this complementary turn-on determined by the control signal for the second time period, thus enabling the MPPT circuit 210 to operate in Boost mode.

[0041] For example, the first upper switch Q1, the first lower switch Q2, the second upper switch Q3, and the second lower switch Q4 can all be metal-oxide-semiconductor field-effect transistors (MOSFETs) or insulated-gate bipolar transistors (IGBTs). This application does not limit the specific type of the switch.

[0042] Before the MPPT circuit 210 performs maximum power point tracking, the controller 220 can simulate a power voltage (PV) curve based on the output voltage of the photovoltaic module 100 and known parameters. For example, the output power is determined based on the output voltage and the following parameters: the number of cells connected in series and in parallel in the photovoltaic module 100, the short-circuit current and open-circuit voltage, the equivalent diode constant, and the thermal voltage.

[0043] For example, the output power can be calculated according to formula (1):

[0044]

[0045] Among them, P pv For the output power of photovoltaic module 100, U pv N is the output voltage of photovoltaic module 100. p The number of cells connected in parallel in a photovoltaic module of 100, N s I represents the number of cells connected in series in a photovoltaic module 100. sc For short-circuit current, V oc V is the open-circuit voltage, a is the equivalent diode constant, and V tThis is the thermal voltage. The equivalent diode constant is determined by the equivalent capacitance and equivalent resistance of the equivalent diode. The equivalent diode is the equivalent diode of the switching transistor in the MPPT circuit 210. V t =NkT / q, where N is Avogadro's constant, k is Boltzmann's constant, q is the amount of charge, and T is the temperature of the photovoltaic module 100.

[0046] Because photovoltaic (PV) modules exhibit non-linear output characteristics, and their output capability is significantly affected by external factors such as light intensity and temperature, maintaining PV modules at their maximum power point (MPP) is challenging. During MPP tracking, the PV curve and MPP continuously change as light intensity and temperature fluctuate. In this process, the tracked power point may deviate from the PV curve, for example... Figure 3 The PV curve shown indicates that the tracked power point is located inside the PV curve. Furthermore, fluctuations in the inductor current within the MPPT circuit can also cause the tracked power point to deviate from the PV curve. When the tracked power point deviates from the PV curve, phenomena such as tracking instability and system malfunction can occur. This can also cause the MPPT algorithm to fail, making it difficult or even impossible to track the maximum power point.

[0047] Based on this, embodiments of this application provide a power control method, power conversion device, and power conversion equipment for an MPPT circuit, aiming to solve the problem of how to bring the power point back to the PV curve when the power point deviates from the PV curve.

[0048] The power control method of the MPPT circuit according to the embodiments of this application will be described below.

[0049] Figure 4 This is a flowchart of a power control method for an MPPT circuit provided in one embodiment of this application.

[0050] The power control method of MPPT circuits can be applied to controllers, for example... Figure 1 The controller 220 is shown. (As shown) Figure 4 As shown, the power control method for an MPPT circuit may include the following steps:

[0051] S401: When the real-time power point of the MPPT circuit deviates from the power voltage curve of the photovoltaic module, calculate the minimum distance from the real-time power point to the power voltage curve based on the real-time power point and the power voltage curve.

[0052] The real-time power point (RTP) is the power point tracked in real time by the MPPT circuit, which corresponds to the actual power output of the photovoltaic (PV) module. At each PTP, the PV module has a corresponding output voltage and a corresponding output power. For example, ... Figure 3As shown, the real-time power point is point P located inside the PV curve, with coordinates (u1, p1). u1 is the output voltage of the photovoltaic module at point P, and p1 is the output power of the photovoltaic module at point P.

[0053] In this embodiment, based on the output voltage and corresponding output power of the photovoltaic module at the real-time power point, and the output voltage and corresponding output power of the photovoltaic module at a specific power point on the PV curve, the minimum distance from the real-time power point to the PV curve is calculated, that is, the distance from the real-time power point to the specific power point.

[0054] S402, determine the target power point corresponding to the minimum distance.

[0055] The target power point is a specific power point on the PV curve. The distance from the real-time power point to the target power point is the minimum distance from the real-time power point to the PV curve.

[0056] S403 outputs a control signal to the MPPT circuit based on the target power point. The control signal is used to control the MPPT circuit to operate at the target power point.

[0057] The control signals include pulse width modulation (PWM) signals. The controller can generate a PWM signal with a specific duty cycle based on the output voltage of the photovoltaic module to control the MPPT circuit to operate at the target power point. When the MPPT circuit operates at the target power point, its input voltage is the output voltage of the photovoltaic module, and the input power is the output power of the photovoltaic module. Therefore, at this time, the photovoltaic module operates at the target power point.

[0058] In this embodiment, during the process of tracking the maximum power point of a photovoltaic module using the MPPT algorithm, when the tracked real-time power point deviates from the PV curve, the minimum distance between the real-time power point and the PV curve is first calculated based on the real-time power point and the PV curve. This minimum distance quantifies the degree of deviation of the real-time power point from the PV curve, and the corresponding target power point is determined based on this minimum distance. Then, a control signal is output to the MPPT circuit based on the target power point. This control signal controls the real-time power point of the MPPT circuit to move towards the target power point, thereby controlling the real-time power point of the MPPT circuit to return to the PV curve. This ensures that the MPPT algorithm can continue to execute, thus improving the stability of the tracking.

[0059] In step S401, see [reference] Figure 5 The minimum distance from the real-time power point to the power voltage curve is calculated based on the real-time power point and the power voltage curve, including the following sub-steps:

[0060] S501 determines the first reference power point and the second reference power point located on the power voltage curve based on the real-time power point and the power voltage curve.

[0061] Wherein, the first power corresponding to the first reference power point is the real-time power of the real-time power point, and the second voltage corresponding to the second reference power point is the real-time voltage of the real-time power point.

[0062] S502 forms a triangular space based on the real-time power point, the first reference power point, and the second reference power point.

[0063] For example, such as Figure 3 As shown, the first reference power point is point B1 on the PV curve, and the coordinates of point B1 are (f -1 (p1),p1). The second reference power point is point A1 on the PV curve, and the coordinates of point A1 are (u1,f(u1)). Where, f -1 (x) is the inverse function of f(x). Points P, A1, and B1 form a triangular space.

[0064] In f -1 (p1) corresponds to two different solutions (e.g., u) p1 and u p2 When calculating the absolute value of the difference between each of the two different solutions and u1 (e.g., |u1|), we can calculate the absolute value of the difference between each solution and u1. p1 -u1| and |u p2 -u1|), the solution with the smaller absolute value of the difference is used as the x-coordinate of point B1.

[0065] S503, iterate through the triangular space until the distance difference between the first distance and the second distance is less than a preset threshold, and then determine the final triangular space.

[0066] Here, the first distance is the distance from the real-time power point to the first reference power point, for example, the first distance is the distance from point P to point B1. The second distance is the distance from the real-time power point to the second reference power point, for example, the second distance is the distance from point P to point A1. After each iteration, both the first and second reference power points in the triangular space lie on the power-voltage curve.

[0067] The preset threshold can be set as needed. For example, the preset threshold can be set to the size of an adjustment step, which is the distance the real-time power point moves towards the target power point within each control cycle. The size of the adjustment step is the absolute value of the change in the output power of the photovoltaic module within each control cycle. The control cycle is determined by the duty cycle of the control signal.

[0068] S504 determines the minimum distance from the real-time power point to the power-voltage curve based on the first and second reference power points in the final triangular space.

[0069] In this embodiment, based on the real-time power and real-time voltage of the real-time power point, the corresponding first reference power point and second reference power point are found on the PV curve. Then, based on the triangular space formed by the real-time power point, the first reference power point, and the second reference power point, the first distance from the real-time power point to the first reference power point and the second distance from the real-time power point to the second reference power point are calculated. When the difference between the first distance and the second distance is greater than or equal to a preset threshold, it indicates that the current triangular space is large. In this case, a new first reference power point and a new second reference power point are found on the PV curve to form a new triangular space. When the difference between the first distance and the second distance is less than the preset threshold, it indicates that the current triangular space is small. The current triangular space is determined as the final triangular space. Then, based on the first reference power point and the second reference power point in the final triangular space, the minimum distance from the real-time power point to the PV curve is determined, thereby ensuring the reliability of the calculated minimum distance.

[0070] In step S503, see [reference needed]. Figure 6 The triangular space is iterated until the difference between the first distance and the second distance is less than a preset threshold, and the final triangular space is determined, including the following sub-steps:

[0071] S601 determines the temporary reference power point on the power-voltage curve based on the first and second reference power points in the triangular space.

[0072] The temporary reference power point is located between the first reference power point and the second reference power point. Figure 3 In this context, the temporary reference power point can be any point between point A1 and point B1 on the PV curve. For example, as... Figure 3 As shown, the temporary reference power point is point C1, located between point B1 and point A1.

[0073] S602, obtain the first distance, the second distance, and the third distance.

[0074] The third distance is the distance from the real-time power point to the temporary reference power point, such as the distance from point P to point C1.

[0075] S603, take the two reference power points corresponding to the two smaller distance values ​​among the first distance, the second distance and the third distance as the new first reference power point and the new second reference power point.

[0076] In this embodiment, when the first distance among the first distance, second distance, and third distance is the largest, the reference power points corresponding to the second distance and the third distance are respectively used as the new first reference power point and the new second reference power point, for example, points A1 and C1 are used as the new first reference power point and the new second reference power point. When the second distance among the first distance, second distance, and third distance is the largest, the reference power points corresponding to the first distance and the third distance are respectively used as the new first reference power point and the new second reference power point, for example, points B1 and C1 are used as the new first reference power point and the new second reference power point.

[0077] S604, the iteratively determined triangular space is determined by the real-time power point, the new first reference power point, and the new second reference power point.

[0078] S605, calculate the first distance between the real-time power point and the first reference power point in the iterated triangular space, and the second distance between the real-time power point and the second reference power point in the iterated triangular space.

[0079] S606, determine whether the distance difference between the first distance after iteration and the second distance after iteration is less than a preset threshold.

[0080] S607, when the distance difference between the first distance after iteration and the second distance after iteration is less than a preset threshold, the triangular space after iteration is taken as the final triangular space.

[0081] If the distance difference between the first distance after iteration and the second distance after iteration is greater than or equal to a preset threshold, return to step S601.

[0082] In this embodiment, when the difference between the first distance and the second distance is greater than or equal to a preset threshold, a temporary reference power point is found between the first and second reference power points to narrow the range of the triangular space, and a third distance from the real-time power point to the temporary reference power point is calculated. Based on the two smaller distance values ​​among the first, second, and third distances, a new first reference power point and a new second reference power point are determined. Then, based on the triangular space formed by the real-time power point, the new first reference power point, and the new second reference power point, a new first distance from the real-time power point to the new first reference power point and a new second distance from the real-time power point to the new second reference power point are calculated. The difference between the new first distance and the new second distance is compared with the preset threshold again. When the difference between the new first distance and the new second distance is greater than or equal to the preset threshold, it indicates that the range of the current triangular space is still large. In this case, the search continues on the PV curve for a new first reference power point and a new second reference power point to form a new triangular space. When the difference between the new first distance and the new second distance is less than the preset threshold, it indicates that the range of the current triangular space is small, and the current triangular space is determined as the final triangular space. This limits the final triangular space to a smaller range, which helps ensure the reliability of the calculated minimum distance.

[0083] In step S601, in one embodiment, determining a temporary reference power point located on the power-voltage curve based on the first and second reference power points in the triangular space includes: averaging the voltage values ​​corresponding to the first and second reference power points in the triangular space to obtain the voltage value corresponding to the temporary reference power point. The power value corresponding to the temporary reference power point is then determined based on the voltage value corresponding to the temporary reference power point and the power-voltage curve.

[0084] In this embodiment, the voltage value corresponding to the temporary reference power point is first determined. The voltage value corresponding to the temporary reference power point is the average of the voltage values ​​corresponding to the first reference power point and the second reference power point. Then, the corresponding power value is determined based on the PV curve and the voltage value, thereby finding the temporary reference power point on the PV curve. For example, Figure 3 The coordinates of the intermediate temporary reference power point C1 can be

[0085] In some embodiments, the voltage value corresponding to the temporary reference power point can be any value between the voltage value corresponding to the first reference power point and the voltage value corresponding to the second reference power point.

[0086] In step S601, in another embodiment, determining a temporary reference power point on the power-voltage curve based on the first and second reference power points in the triangular space includes: averaging the power values ​​corresponding to the two reference power points in the triangular space to obtain the power value corresponding to the temporary reference power point; and determining the voltage value corresponding to the temporary reference power point based on the power value corresponding to the temporary reference power point and the power-voltage curve.

[0087] In this embodiment, the power value corresponding to the temporary reference power point is first determined. The power value corresponding to the temporary reference power point is the average of the power values ​​corresponding to the first reference power point and the second reference power point. Then, the corresponding voltage value is determined based on the PV curve and the power value, thereby finding the temporary reference power point on the PV curve. For example, the temporary power reference point is at this time... Figure 3 The coordinates in can be

[0088] In some embodiments, the power value corresponding to the temporary reference power point can be any value between the power value corresponding to the first reference power point and the power value corresponding to the second reference power point.

[0089] In step S504, determining the minimum distance from the real-time power point to the power-voltage curve based on the first and second reference power points in the final triangular space includes: determining the reference power point with the larger power value among the first and second reference power points in the final triangular space. The distance from the real-time power point to the reference power point with the larger power value is then determined as the minimum distance.

[0090] In this embodiment, the power value corresponding to the first reference power point in the final triangular space is compared with the power value corresponding to the second reference power point to find the reference power point with the larger power value. Then, the distance from the real-time power point to the reference power point with the larger power value is calculated to determine the minimum distance, where the reference power point with the larger power value is the target power point corresponding to the minimum distance.

[0091] In step S403, see [reference needed] Figure 7 The control signal is output to the MPPT circuit according to the target power point, including the following sub-steps:

[0092] S701 determines the input voltage reference value and inductor current limit value of the MPPT circuit based on the target power point.

[0093] The input voltage reference value is the output voltage of the photovoltaic module at the target power point, and the inductor current limit value is a preset current value calculated based on the output voltage and output power of the photovoltaic module at the target power point.

[0094] For example, if the coordinates of the target power point are (u n,f(u n If the minimum distance is ), then the minimum distance is The preset current value is calculated based on the output voltage and output power of the photovoltaic module at the target power point.

[0095] S702 determines the duty cycle of the control signal for the MPPT circuit based on the input voltage reference value, the inductor current limit value, and the preset loop control model.

[0096] In this embodiment, the preset loop control model is used to determine the duty cycle of the control signal of the MPPT circuit based on the input voltage and output voltage of the MPPT circuit, as well as the input voltage reference value and the inductor current limiting value.

[0097] For example, such as Figure 8 As shown, the preset loop control model 800 includes a first voltage loop 810, a second voltage loop 820, a comparator 830, and a current loop 840. The first voltage loop 810 includes a first adder / subtractor 811 and a first PID (Proportional-Integral-Derivative) controller 812. The second voltage loop 820 includes a second adder / subtractor 821 and a second PID controller 822. The current loop 840 includes a third adder / subtractor 841, a current limiter 842, and a third PID controller 843.

[0098] In the first voltage loop 810, the first adder / subtractor 811 is used to adjust the input voltage U of the MPPT circuit. in and input voltage reference value U n Calculate the input voltage U of the MPPT circuit. in and input voltage reference value U n The difference. The first PID controller 812 is used to control the input voltage U of the MPPT circuit. in and input voltage reference value U n The difference is used for proportional, integral, and derivative control to obtain the first current output Iout1.

[0099] In the second voltage loop 820, the second adder / subtractor 821 is used to adjust the output voltage U of the MPPT circuit. out and the preset output voltage reference value U outref Calculate the output voltage U of the MPPT circuit. out and output voltage reference value U outref The difference. Wherein, the output voltage reference value U outref Determined based on bus voltage. The second PID controller 822 is used to control the output voltage U of the MPPT circuit. out and output voltage reference value Uoutref The difference is used for proportional, integral, and derivative control to obtain the second current output Iout2.

[0100] Comparator 830 is used to calculate the smaller of the first current output Iout1 and the second current output Iout2 based on the first current output Iout1 and the second current output Iout2, and use it as the current reference value Iref of the current loop 840.

[0101] In the current loop 840, the third adder / subtractor 841 is used to calculate the current reference value Iref and the real-time inductor current value I of the MPPT circuit. L Calculate the current reference value Iref and the real-time inductor current value I of the MPPT circuit. L The difference ΔI is used. The third PID controller 843 is used to perform proportional, integral, and derivative control on the difference ΔI to obtain the expected value I of the inductor current at the next moment. L * The current limiter 842 is used to limit the desired value I of the inductor current. L * Limiting is performed, based on the expected value I of the inductor current after limiting. L * In addition to the impedance of the MPPT circuit, the duty cycle D of the control signal of the MPPT circuit at the next moment can be calculated.

[0102] S703 outputs control signals to the MPPT circuit based on the duty cycle.

[0103] In this embodiment, a preset current value is calculated based on the output voltage and output power of the photovoltaic module at the target power point. The output voltage of the photovoltaic module at the target power point is then set as the input voltage reference value of the MPPT circuit, and the preset current value is set as the inductor current limit value. Next, the input voltage reference value and the inductor current limit value are used as parameters of a preset loop control model. Based on the duty cycle of the control signal output by the preset loop control model, a control signal is output to the MPPT circuit. Based on the control signal, the real-time current value in the MPPT circuit continuously increases, and the real-time power point gradually moves towards the target power point. When the real-time current value in the MPPT circuit reaches the inductor current limit value, the real-time power point overlaps with the target power point, and at this point, the real-time power point returns to the PV curve. Since the distance from the real-time power point back to the PV curve is the minimum distance, the tracking delay to the target power point can be reduced, thereby improving tracking efficiency.

[0104] In some embodiments, the preset loop control model includes a voltage loop and a current loop, and the adjustment step size of the voltage loop is determined based on the minimum distance.

[0105] In this embodiment, the minimum distance is divided into multiple distance segments, each representing an adjustment step size. Based on the control signal, the real-time power point moves towards the target power point in increments of one adjustment step size until it overlaps with the target power point. This helps reduce situations where the real-time power point exceeds or fails to reach the target power point during tracking due to calculation errors, thereby improving tracking accuracy.

[0106] For example, if the coordinates of the target power point are (u n ,f(u n If the minimum distance is ), then the minimum distance is The adjustment step size is s = L n / k, where k is a constant. M≤s≤N, where M is the first step threshold and N is the second step threshold. Setting a first step threshold helps reduce the situation where the power point cannot be adjusted to the PV curve for a long time due to slow tracking speed. Setting a second step threshold helps reduce overshoot and overshoot caused by rapid voltage and current changes in the MPPT circuit. When the adjustment step size is less than the first step threshold or greater than the second step threshold, the k value is adjusted to make the adjustment step size greater than or equal to the first step threshold and less than or equal to the second step threshold.

[0107] Figure 9 This is a structural block diagram of a power conversion device provided in one embodiment of this application.

[0108] like Figure 9 As shown, the power conversion device 900 is electrically connected to the MPPT circuit, and the MPPT circuit is electrically connected to the photovoltaic module. The power conversion device 900 includes a minimum distance calculation module 910, a target power point determination module 920, and a control signal output module 930.

[0109] The minimum distance calculation module 910 is used to calculate the minimum distance from the real-time power point to the power voltage curve based on the real-time power point and the power voltage curve when the real-time power point of the MPPT circuit deviates from the power voltage curve of the photovoltaic module.

[0110] The target power point determination module 920 is used to determine the target power point corresponding to the minimum distance.

[0111] The control signal output module 930 is used to output a control signal to the MPPT circuit according to the target power point. The control signal is used to control the MPPT circuit to operate at the target power point.

[0112] It is understood that the module division described above is a logical functional division, and there may be other division methods in actual implementation. Furthermore, the functional modules in the various embodiments of this application can be integrated into the same processing unit, or each module can exist physically separately, or two or more modules can be integrated into the same unit. The integrated modules described above can be implemented in hardware or in a combination of hardware and software functional modules.

[0113] Figure 10 This is a structural block diagram of a power conversion device provided in one embodiment of this application.

[0114] like Figure 10 As shown, the power conversion device 200 includes an MPPT circuit 210, a controller 220, and a memory 230. The MPPT circuit 210 is used to be electrically connected to the photovoltaic module, the memory 230 is used to store instructions, and the controller 220 is used to run the instructions stored in the memory 230, so that the power conversion device 200 executes the power control method of the MPPT circuit of the present application embodiment.

[0115] The controller 220 can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0116] This application provides a computer-readable storage medium for storing instructions that, when executed by a computer, cause the computer to perform the power control method of the MPPT circuit of this application.

[0117] Computer-readable storage media include volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules or other data). Computer-readable storage media include, but are not limited to, random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical disc storage, magnetic cartridges, magnetic tapes, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. A method of power control for an MPPT circuit, characterized by, The MPPT circuit is electrically connected to the photovoltaic module, and the method includes: When the real-time power point of the MPPT circuit deviates from the power voltage curve of the photovoltaic module, the minimum distance from the real-time power point to the power voltage curve is calculated based on the real-time power point and the power voltage curve. Determine the target power point corresponding to the minimum distance; A control signal is output to the MPPT circuit according to the target power point, and the control signal is used to control the MPPT circuit to operate at the target power point.

2. The power control method of claim 1, wherein, The step of calculating the minimum distance from the real-time power point to the power voltage curve based on the real-time power point and the power voltage curve includes: A first reference power point and a second reference power point located on the power voltage curve are determined based on the real-time power point and the power voltage curve; wherein, the first power corresponding to the first reference power point is the real-time power of the real-time power point, and the second voltage corresponding to the second reference power point is the real-time voltage of the real-time power point; A triangular space is formed based on the real-time power point, the first reference power point, and the second reference power point; The triangular space is iterated until the difference between the first distance and the second distance is less than a preset threshold, and the final triangular space is determined; wherein, after each iteration, the first reference power point and the second reference power point of the triangular space are both located on the power voltage curve, the first distance is the distance from the real-time power point to the first reference power point, and the second distance is the distance from the real-time power point to the second reference power point; The minimum distance from the real-time power point to the power-voltage curve is determined based on the first reference power point and the second reference power point in the final triangular space.

3. The power control method of claim 2, wherein, The step of iterating through the triangular space until the distance difference between the first distance and the second distance is less than a preset threshold, and then determining the final triangular space, includes: A temporary reference power point is determined on the power-voltage curve based on the first reference power point and the second reference power point in the triangular space, wherein the temporary reference power point is located between the first reference power point and the second reference power point. Obtain the first distance, the second distance, and the third distance, wherein the third distance is the distance from the real-time power point to the temporary reference power point; The two reference power points corresponding to the two smaller distance values ​​among the first distance, the second distance, and the third distance are used as the new first reference power point and the new second reference power point; The iteratively defined triangular space is determined by the real-time power point, the new first reference power point, and the new second reference power point. Calculate the first distance between the real-time power point and the first reference power point of the iterated triangular space, and the second distance between the real-time power point and the second reference power point of the iterated triangular space; If the distance difference between the first distance and the second distance after iteration is greater than or equal to a preset threshold, return to the step of determining a temporary reference power point on the power voltage curve based on the first reference power point and the second reference power point in the triangular space; When the distance difference between the first distance and the second distance after iteration is less than a preset threshold, the triangular space after iteration is taken as the final triangular space.

4. The power control method of claim 3, wherein, Determining the temporary reference power point located on the power-voltage curve based on the first and second reference power points in the triangular space includes: The voltage value corresponding to the first reference power point and the voltage value corresponding to the second reference power point in the triangular space are averaged to obtain the voltage value corresponding to the temporary reference power point. The power value corresponding to the temporary reference power point is determined based on the voltage value corresponding to the temporary reference power point and the power-voltage curve.

5. The power control method as described in claim 3, characterized in that, Determining the temporary reference power point located on the power-voltage curve based on the first and second reference power points in the triangular space includes: The power value corresponding to the temporary reference power point is obtained by averaging the power values ​​corresponding to the two reference power points in the triangular space. The voltage value corresponding to the temporary reference power point is determined based on the power value corresponding to the temporary reference power point and the power-voltage curve.

6. The power control method as described in claim 2, characterized in that, Determining the minimum distance from the real-time power point to the power-voltage curve based on the first reference power point and the second reference power point in the final triangular space includes: Determine the reference power point with the larger power value among the first and second reference power points in the final triangular space; The distance from the real-time power point to the reference power point with the larger power value is determined as the minimum distance.

7. The power control method of claim 1, wherein, The step of outputting a control signal to the MPPT circuit according to the target power point includes: The input voltage reference value and inductor current limit value of the MPPT circuit are determined based on the target power point. The duty cycle of the control signal for the MPPT circuit is determined based on the input voltage reference value, the inductor current limiting value, and the preset loop control model. Based on the duty cycle, a control signal is output to the MPPT circuit.

8. The power control method of claim 7, wherein, The preset loop control model includes a voltage loop and a current loop, and the adjustment step size of the voltage loop is determined based on the minimum distance.

9. A power conversion device, characterized by, The power conversion device is electrically connected to the MPPT circuit, and the MPPT circuit is electrically connected to the photovoltaic module. The power conversion device includes: The minimum distance calculation module is used to calculate the minimum distance from the real-time power point to the power voltage curve based on the real-time power point and the power voltage curve when the real-time power point of the MPPT circuit deviates from the power voltage curve of the photovoltaic module. The target power point determination module is used to determine the target power point corresponding to the minimum distance; A control signal output module is used to output a control signal to the MPPT circuit according to the target power point, and the control signal is used to control the MPPT circuit to operate at the target power point.

10. A power conversion device, characterized by, The power conversion device includes an MPPT circuit, a memory, and a controller. The MPPT circuit is used to be electrically connected to a photovoltaic module. The memory is used to store instructions. The controller is used to execute the instructions stored in the memory, causing the power conversion device to perform the power control method of the MPPT circuit as described in any one of claims 1 to 8.

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