Self-correcting photovoltaic optimizer with photovoltaic system

Abstract

The application provides a self-correcting photovoltaic optimizer, comprising a transformer module, an adjusting module, a driving module and a sampling module; wherein the first end of the transformer module is connected with an input voltage end, the second end of the transformer module is connected with the input end of the sampling module, the output end of the sampling module is connected with the first end of the adjusting module, the second end of the adjusting module is connected with the input voltage end, the third end of the adjusting module is connected with the input end of the driving module, the first output end of the driving module is connected with the fourth end of the adjusting module, the second output end of the driving module is connected with the third end of the transformer module, and the second end of the transformer module is also connected with an output voltage end; the adjusting module is configured to determine the maximum output power according to the current output power and output a first reference voltage; the first reference voltage represents the corresponding input voltage under the maximum output power.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic power generation, and more particularly to a self-calibrating photovoltaic optimizer and photovoltaic system. Background Technology

[0002] Photovoltaic optimizers can achieve module-level MPPT, decoupling input and output, and solving the problem of power generation loss caused by series-parallel mismatch in photovoltaic systems.

[0003] Currently, after a photovoltaic system is equipped with a photovoltaic optimizer, when the output voltage of the photovoltaic optimizer is lower than the output voltage of the maximum power point, the power is always maintained at the maximum power point. Therefore, the inverter cannot determine the maximum power point of the photovoltaic modules, and thus cannot make the photovoltaic system operate at maximum power. This results in the inverter's actual operating voltage being lower than normal, reducing its operating efficiency. Summary of the Invention

[0004] This invention provides a self-calibrating photovoltaic optimizer and photovoltaic system to solve the problem of being unable to determine the maximum power point.

[0005] According to a first aspect of the present invention, a self-calibrating photovoltaic optimizer is provided, comprising: a converter module, an adjustment module, a drive module, and a sampling module;

[0006] The converter module has a first terminal connected to an input voltage terminal, a second terminal connected to the input terminal of the sampling module, an output terminal connected to the first terminal of the adjustment module, a second terminal connected to the input voltage terminal, a third terminal connected to the input terminal of the drive module, a first output terminal connected to the fourth terminal of the adjustment module, a second output terminal connected to the third terminal of the converter module, and a second terminal also connected to an output voltage terminal for outputting the operating voltage.

[0007] The sampling module is configured to: sample the output voltage and output current in real time, and output the current output power;

[0008] The adjustment module is configured to: determine the maximum output power based on the current output power, and output a first reference voltage; the first reference voltage represents the input voltage corresponding to the maximum output power;

[0009] The drive module is configured to output a drive signal to the converter module based on the first reference voltage;

[0010] The converter module is configured to be controlled by the drive signal and to output the operating voltage based on the drive signal.

[0011] Optionally, the adjustment module includes an integral circuit, a proportional circuit, a first adder, an MPPT control module, and a second adder;

[0012] Wherein, the first output terminal of the driving module is connected to the input terminal of the integrator circuit, the output terminal of the integrator circuit is connected to the input terminal of the proportional circuit, the output terminal of the proportional circuit is connected to the first terminal of the first adder, the second terminal of the first adder is connected to the input terminal of the MPPT control module, the third terminal of the first adder is connected to the output terminal of the sampling module, the output terminal of the MPPT control module is connected to the first terminal of the second adder, the second terminal of the second adder is connected to the input terminal of the driving module, and the third terminal of the second adder is connected to the input voltage terminal;

[0013] The integrator circuit is configured to: set an integral coefficient ∫Dr for the first drive signal output by the drive module, and output the integral coefficient ∫Dr to the proportional circuit;

[0014] The proportional circuit is configured to: perform proportional operation on the integral coefficient ∫Dr by adjusting the proportional coefficient K, so as to output a first proportional amplitude K*∫Dr to the first adder;

[0015] The first adder is configured to: take the difference between the first proportional amplitude K*∫Dr and the current output power, and output the first difference value to the MPPT control module;

[0016] The MPPT control module is configured to output the first reference voltage to the second adder based on the first difference.

[0017] The second adder is configured to take the difference between the first reference voltage and the input voltage, and output a second difference value to the drive module.

[0018] Optionally, the adjustment module further includes a first comparator; the non-inverting input of the first comparator is connected to the output of the integrator circuit, the inverting input of the first comparator is connected to a reference voltage terminal for inputting a second reference voltage, and the output of the first comparator is connected to the input of the proportional circuit.

[0019] The first comparator is configured to compare the integral coefficient ∫Dr with the second reference voltage to output a first signal or a second signal.

[0020] Optionally, the first comparator is further configured to:

[0021] When the integral coefficient ∫Dr is above the second reference voltage, the first comparator outputs a first signal;

[0022] When the integral coefficient ∫Dr is less than the second reference voltage, the first comparator outputs a second signal.

[0023] Optionally, the proportional circuit is further configured to:

[0024] When the input signal is the first signal, the proportional circuit outputs a second proportional amplitude.

[0025] When the input signal is the second signal, the proportional circuit outputs a third proportional amplitude.

[0026] Optionally, the sampling module includes: a current sampling unit, a voltage sampling unit, and a multiplier;

[0027] The input terminals of the current sampling unit and the voltage sampling unit are both connected to the converter module, the output terminals of the current sampling unit and the voltage sampling unit are both connected to the first terminal and the second terminal of the multiplier, and the third terminal of the multiplier is connected to the first adder.

[0028] The multiplier is configured to multiply the output voltage and the output current to output the current output power.

[0029] Optionally, the drive module includes: a PID control unit, a second comparator, and a driver;

[0030] Wherein, the input terminal of the PID control unit is connected to the first terminal of the second adder, the output terminal of the PID control unit is connected to the non-inverting input terminal of the second comparator, the inverting input terminal of the second comparator is connected to an input waveform terminal for inputting an input waveform, the output terminal of the second comparator is connected to the input terminal of the driver, the first output terminal of the driver is connected to the input terminal of the integrator circuit, and the second output terminal of the driver is connected to the third terminal of the converter module;

[0031] The PID control unit is configured to control the second difference to tend towards infinitesimal and output a PID output value to the non-inverting input of the second comparator;

[0032] The second comparator is configured to intersect the PID output value with the input waveform to output a second drive signal and a third drive signal.

[0033] The driver is configured to amplify the second drive signal and the third drive signal to drive the converter module.

[0034] Optionally, the converter module includes: a first switching transistor, a second switching transistor, an inductor, a first capacitor, and a second capacitor;

[0035] Wherein, the control terminal of the first switching transistor is connected to the first output terminal of the driver, the first terminal of the first switching transistor is connected to the input voltage terminal, the second output terminal of the first switching transistor is connected to the first terminal of the second switching transistor and the first terminal of the inductor, the second terminal of the second switching transistor is connected to the first terminal of the first capacitor, the second terminal of the inductor is connected to the second terminal of the first capacitor, and the second capacitor is connected in parallel with the first capacitor and the output voltage terminal.

[0036] The first and second switching transistors are configured to be controlled by the second drive signal and the third drive signal, and to output the operating voltage based on the ratio of the second drive signal and the third drive signal.

[0037] Optionally, the converter module includes a BUCK converter or a BUCK-BOOST converter.

[0038] Optionally, the first switch and the second switch may be NMOS or PMOS transistors.

[0039] According to a second aspect of the present invention, a photovoltaic system is provided, comprising: a plurality of photovoltaic modules, an inverter, a power grid, and a plurality of self-calibrating photovoltaic optimizers as described in the first aspect and optionally thereof;

[0040] The photovoltaic modules are connected in series, and the output terminals of the photovoltaic modules are connected to the input terminals of the self-calibrating photovoltaic optimizers. The output terminals of the self-calibrating photovoltaic optimizers are connected to the input terminals of the inverter, and the output terminals of the inverter are connected to the power grid.

[0041] The self-calibrating photovoltaic optimizer and photovoltaic system provided by this invention can adjust the output power through an adjustment module to achieve changes in the output power, thereby enabling the determination of the maximum output power based on the output power and outputting the voltage corresponding to the maximum output power, thus improving the conversion efficiency of the inverter.

[0042] Furthermore, in a preferred embodiment, the present invention adjusts the proportional amplitude to adjust the difference between the proportional amplitude and the current output power, further adjusts the rate of change of the output power, and ultimately determines the maximum output power. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the optimizer structure in the prior art of this invention;

[0045] Figure 2 This is a PV curve diagram of the photovoltaic array at the input terminal of the inverter in the prior art of this invention;

[0046] Figure 3 This is the PV curve of the photovoltaic array input to the inverter after adding an optimizer in the prior art of this invention. Figure 1 ;

[0047] Figure 4 This is the PV curve of the photovoltaic array input to the inverter after adding an optimizer in the prior art of this invention. Figure 2 ;

[0048] Figure 5 This is a schematic diagram of the structure of a self-calibrating photovoltaic optimizer in one embodiment of the present invention. Figure 1 ;

[0049] Figure 6 This is a schematic diagram of the structure of a self-calibrating photovoltaic optimizer in one embodiment of the present invention. Figure 2 ;

[0050] Figure 7 This is a schematic diagram of the structure of a self-calibrating photovoltaic optimizer in one embodiment of the present invention. Figure 3 ;

[0051] Figure 8 This is the PV curve of a photovoltaic system after adding a self-calibrating photovoltaic optimizer in one embodiment of the present invention. Figure 1 ;

[0052] Figure 9 This is the PV curve of a photovoltaic system after adding a self-calibrating photovoltaic optimizer in one embodiment of the present invention. Figure 2 ;

[0053] Figure 10 This is a schematic diagram of the converter module structure in a self-calibrating photovoltaic optimizer according to an embodiment of the present invention. Figure 1 ;

[0054] Figure 11 This is a schematic diagram of the converter module structure in a self-calibrating photovoltaic optimizer according to an embodiment of the present invention. Figure 2 ;

[0055] Figure 12 This is a schematic diagram of the structure of a photovoltaic system in one embodiment of the present invention.

[0056] Explanation of reference numerals in the attached figures:

[0057] 1-Converter module;

[0058] 101 - First switching transistor;

[0059] 102 - Second switching transistor;

[0060] 103 - Inductor;

[0061] 104 - First capacitor;

[0062] 105 - Second capacitor;

[0063] 2-Sampling module;

[0064] 201 - Current sampling unit;

[0065] 202 - Voltage sampling unit;

[0066] 203 - Multiplier;

[0067] 3-Adjustment module;

[0068] 301 - Integrating Circuit;

[0069] 302 - Proportional Circuit;

[0070] 303 - First Adder;

[0071] 304-MPPT control module;

[0072] 305 - Second Adder;

[0073] 306 - First comparator;

[0074] 4-Driver module;

[0075] 401-PID control unit;

[0076] 402 - Second comparator;

[0077] 403 - Driver. Detailed Implementation

[0078] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0079] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0080] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0081] Prior to filing this application, the applicant conducted thorough research on photovoltaic optimizers and, based on that research, proposed... Figure 1 The photovoltaic optimizer shown is for Figure 1 The photovoltaic optimizer shown includes a converter module, a sampling module, and a drive module. The converter module includes a first switch, a second switch, an inductor, a first capacitor, and a second capacitor. The sampling module includes a current sampling unit, a voltage sampling unit, and a multiplier. The drive module includes an MPPT control module, an adder, a PID control unit, a comparator, and a driver.

[0082] In this configuration, the control terminal of the first switching transistor is connected to the first output terminal of the driver; the first terminal of the first switching transistor is connected to an input voltage terminal; the second output terminal of the first switching transistor is connected to the first terminal of the second switching transistor and the first terminal of the inductor; the second terminal of the second switching transistor is connected to the first terminal of the first capacitor; the second terminal of the inductor is connected to the second terminal of the first capacitor; the second capacitor, the first capacitor, and the output voltage terminal are connected in parallel; the input terminals of the current sampling unit and the voltage sampling unit are both connected to the converter module; the output terminals of the current sampling unit and the voltage sampling unit are both connected to the first and second terminals of the multiplier; the third terminal of the multiplier is connected to the input terminal of the MPPT control module; the output terminal of the MPPT control module is connected to the first terminal of the adder; the second terminal of the adder is connected to the input terminal of the PID control unit; the third terminal of the adder is connected to the input voltage terminal; the output terminal of the PID control unit is connected to the non-inverting input terminal of the comparator; the inverting input terminal of the comparator is connected to an input waveform terminal for inputting an input waveform; the output terminal of the comparator is connected to the input terminal of the driver; and the output terminal of the driver is connected to the converter module.

[0083] Please refer to Figure 2 , Figure 2 The figure shows the PV curve of the photovoltaic array at the input of the inverter without a photovoltaic optimizer. As can be seen from the figure, in a photovoltaic system without an optimizer, the photovoltaic modules are connected in series and then in parallel. The working PV curve characteristics are the same as those of the photovoltaic modules. There are large slopes to the left and right at the maximum power point (i.e., point M), which leads to a large power variation and thus reduces the output power.

[0084] Please refer to the above options. Figure 3 as well as Figure 4 , Figure 3 as well as Figure 4 The figure shows the PV curve of the photovoltaic array input to the inverter after adding a photovoltaic optimizer. As can be seen from the figure, when the input voltage of the inverter after adding the photovoltaic optimizer is lower than the voltage corresponding to the maximum power point (i.e., point M), the power of the photovoltaic optimizer is always maintained at the maximum power of point M. Therefore, the PV curve of the system after adding the optimizer becomes almost horizontal from point M to the left. Since the power remains unchanged, the actual operating point of the inverter is lower, resulting in a larger voltage drop of the optimizer and a larger voltage rise of the inverter, which in turn leads to a decrease in the efficiency of the optimizer and the inverter.

[0085] In view of this, the present invention proposes a self-calibrating photovoltaic optimizer. By adding an adjustment module, it can adjust the PV curve output by the photovoltaic system to achieve the goal of not affecting the power at the maximum power point, while avoiding the problem of reduced efficiency of the optimizer and inverter caused by a large voltage drop of the inverter.

[0086] The specific details of the solution of this invention are as follows:

[0087] Please refer to Figure 5 The present invention provides a self-calibrating photovoltaic optimizer, comprising: a converter module 1, an adjustment module 3, a drive module 4, and a sampling module 2;

[0088] Wherein, the first end of the converter module 1 is connected to an input voltage terminal, the second end of the converter module 1 is connected to the input terminal of the sampling module 2, the output terminal of the sampling module 2 is connected to the first end of the adjustment module 3, the second end of the adjustment module 3 is connected to the input voltage terminal, the third end of the adjustment module 3 is connected to the input terminal of the drive module 4, the first output terminal of the drive module 4 is connected to the fourth end of the adjustment module 3, the second output terminal of the drive module 4 is connected to the third end of the converter module 1, and the second end of the converter module 1 also has an output voltage terminal for outputting the working voltage;

[0089] The sampling module 2 is configured to: sample the output voltage and output current in real time, and output the current output power;

[0090] The adjustment module 3 is configured to: determine the maximum output power based on the current output power, and output a first reference voltage; the first reference voltage represents the input voltage corresponding to the maximum output power;

[0091] The drive module 4 is configured to output a drive signal to the converter module 1 based on the first reference voltage;

[0092] The converter module 1 is configured to be controlled by the drive signal and to output the operating voltage based on the drive signal.

[0093] In a preferred embodiment, please refer to Figure 10 as well as Figure 11 The converter module 1 includes a BUCK converter or a BUCK-BOOST converter.

[0094] Of course, the present invention is not limited thereto, and other forms of converter module 1 are all within the protection scope of the present invention.

[0095] Regarding adjustment module 3, in a preferred embodiment, please refer to... Figure 6 The adjustment module 3 includes an integral circuit 301, a proportional circuit 302, a first adder 303, an MPPT control module 304, and a second adder 305.

[0096] Wherein, the first output terminal of the driving module 4 is connected to the input terminal of the integrator circuit 301, the output terminal of the integrator circuit 301 is connected to the input terminal of the proportional circuit 302, the output terminal of the proportional circuit 302 is connected to the first terminal of the first adder 303, the second terminal of the first adder 303 is connected to the input terminal of the MPPT control module 304, the third terminal of the first adder 303 is connected to the output terminal of the sampling module 2, the output terminal of the MPPT control module 304 is connected to the first terminal of the second adder 305, the second terminal of the second adder 305 is connected to the input terminal of the driving module 4, and the third terminal of the second adder 305 is connected to the input voltage terminal;

[0097] The integrator circuit 301 is configured to: set an integral coefficient ∫Dr for the first drive signal output by the drive module 4, and output the integral coefficient ∫Dr to the proportional circuit 302;

[0098] The proportional circuit 302 is configured to: perform proportional operation on the integral coefficient ∫Dr by adjusting the proportional coefficient K, so as to output a first proportional amplitude K*∫Dr to the first adder 303;

[0099] The first adder 303 is configured to: take the difference between the first proportional amplitude K*∫Dr and the current output power, and output the first difference value to the MPPT control module 304;

[0100] The MPPT control module 304 is configured to output the first reference voltage to the second adder 305 based on the first difference.

[0101] The second adder 305 is configured to take the difference between the first reference voltage and the input voltage, and output a second difference value to the drive module 4.

[0102] In one example, when Dr = 1, ∫Dr = ∫1 = 1, that is, the coefficient of the integrator circuit 301 is set to 1 so that the first proportional amplitude K*∫Dr is K.

[0103] Regarding sampling module 2, in a preferred embodiment, please refer to [link / reference needed]. Figure 6 The sampling module 2 includes: a current sampling unit 201, a voltage sampling unit 202, and a multiplier 203;

[0104] The input terminals of the current sampling unit 201 and the voltage sampling unit 202 are both connected to the converter module 1, the output terminals of the current sampling unit 201 and the voltage sampling unit 202 are both connected to the first terminal and the second terminal of the multiplier 203, and the third terminal of the multiplier 203 is connected to the first adder 303.

[0105] The multiplier 203 is configured to multiply the output voltage and the output current to output the current output power.

[0106] Regarding driver module 4, in a preferred embodiment, please refer to [link / reference needed]. Figure 6 The drive module 4 includes: a PID control unit 401, a second comparator 402, and a driver 403;

[0107] The PID control unit 401 has its input terminal connected to the first terminal of the second adder 305, its output terminal connected to the non-inverting input terminal of the second comparator 402, its inverting input terminal connected to an input waveform terminal for inputting an input waveform, its output terminal connected to the input terminal of the driver 403, its first output terminal connected to the input terminal of the integrator circuit 301, and its second output terminal connected to the third terminal of the converter module 1.

[0108] The PID control unit 401 is configured to control the second difference to tend towards infinitesimal and output a PID output value to the non-inverting input of the second comparator 402;

[0109] The second comparator 402 is configured to intersect the PID output value with the input waveform to output a second drive signal and a third drive signal.

[0110] The driver 403 is configured to amplify the second drive signal and the third drive signal to drive the converter module 1.

[0111] In one embodiment, the input waveform includes a triangular waveform.

[0112] Of course, this invention is not limited to this, and other waveform forms are all within the protection scope of this invention.

[0113] Specifically, the ratio of the intersection of the PID output value and the input waveform is the drive duty cycle.

[0114] Regarding converter module 1, in a preferred embodiment, please refer to [link / reference needed]. Figure 6 The converter module 1 includes: a first switch 101, a second switch 102, an inductor 103, a first capacitor 104, and a second capacitor 105;

[0115] Wherein, the control terminal of the first switch 101 is connected to the first output terminal of the driver 403, the first terminal of the first switch 101 is connected to the input voltage terminal, the second output terminal of the first switch 101 is connected to the first terminal of the second switch 102 and the first terminal of the inductor 103, the second terminal of the second switch 102 is connected to the first terminal of the first capacitor 104, the second terminal of the inductor 103 is connected to the second terminal of the first capacitor 104, and the second capacitor 105 is connected in parallel with the first capacitor 104 and the output voltage terminal;

[0116] The first switch 101 and the second switch 102 are configured to be controlled by the second drive signal and the third drive signal, and to output the operating voltage based on the ratio of the second drive signal and the third drive signal.

[0117] In one example, the first switch 101 and the second switch 102 include NMOS transistors or PMOS transistors.

[0118] Of course, this invention is not limited thereto, and other forms of switching transistors are all within the protection scope of this invention.

[0119] In a specific embodiment, the lowest and highest points of the input waveform are 0 and 1, and the period is 10 microseconds. In one example, the PID output value intersects in the middle of the input waveform, that is, the duty cycle is 0.5, and the first switch 101 and the second switch 102 are both turned on for 5 microseconds.

[0120] In other examples, the PID output value is 0.3 from the highest point and 0.7 from the lowest point, that is, the duty cycle is 0.3, the first switch 101 is turned on for 3 microseconds, and the second switch 102 is turned on for 7 microseconds.

[0121] In the above scheme, the duty cycle is adjusted by adjusting the PID output value, thereby ultimately adjusting the input voltage. Specifically, the output voltage VOUT = VIN * D, where D is the duty cycle.

[0122] Regarding the working process of the self-calibrating photovoltaic optimizer described in the above scheme, in a specific embodiment, firstly, the current sampling unit 201 and the voltage sampling unit 202 detect the output current and output voltage respectively, and multiply the output current and output voltage to obtain the output power Pout; secondly, the driver 403 outputs a drive Dr (i.e., the first drive signal) to the integrator circuit 301, and the integrator circuit 301 calculates ∫Dr, which is proportional to the drive duty cycle. The integrator circuit 301 outputs ∫Dr to the proportional circuit 302, and the proportional circuit 302 then adjusts the amplitude to obtain k*∫Dr (i.e., the proportional amplitude). Then, by subtracting the output power Pout (i.e., the current output power) from the output k*∫Dr (i.e., the proportional amplitude) output by the proportional circuit 302, the difference is output to the MPPT control module 304. Through the comparison of the algorithm in the MPPT control module 304, the input voltage Vin_ref (i.e., the first reference voltage) corresponding to the maximum power is output. Then, the input voltage Vin_ref (i.e., the first reference voltage) is subtracted from the input voltage Vin, and the difference is output to the PID control unit 401. The drive signal is obtained by intersecting the output of the PID control unit 401 with an input waveform, so as to drive the two switching transistors of the converter module 1.

[0123] For details, please refer to Figure 8 , Figure 8 The figure shows the PV curves of the system before and after adding a self-calibrating photovoltaic optimizer. As can be seen from the figure, the PV curve of the system with a conventional optimizer (i.e., the PV curve before calibration) has a slope of 0 to the left of point M. This means that no matter how the output voltage changes, the power always remains at the maximum power. This causes the subsequent inverter to be unable to determine the voltage at the maximum power point, resulting in a lower actual operating voltage, a larger boost voltage from the optimizer, and a larger voltage drop voltage from the inverter. This further leads to lower efficiency of both the optimizer and the inverter, and also reduces the power generation of the photovoltaic system. On the other hand, the PV curve of the system with a self-calibrating photovoltaic optimizer (i.e., the PV curve after calibration) has a slope of non-zero to the left of point M. This means that the power changes with the output voltage. Therefore, the inverter can determine the maximum power and the corresponding output voltage Vmp based on the judgment and comparison of the power.

[0124] For further information, please refer to the following: Figure 8When the photovoltaic optimizer operates in shoot-through mode, its efficiency is highest, resulting in the maximum output power. This means both the input and output of the photovoltaic optimizer are at the module's maximum power point (M point), and both the input and output voltages are Vmp (output voltage). In this mode, the first switch 101 of the buck circuit is shoot-through, and the duty cycle of the freewheeling diode is 0. If the photovoltaic optimizer steps down the voltage, Dr > 0, and the greater the step-down, the larger Dr becomes. The integral value of Dr also increases, leading to a larger proportional gain after passing through the proportional circuit. Consequently, the difference between the output power Pout and the proportional gain output by the proportional circuit becomes smaller. Figure 8 The corrected PV curve is shown.

[0125] Furthermore, the slope of the PV curve is: [(Pmax-k*∫0)-(Pmax-k*∫1)] / Vmp=K / Vmp; where Pmax is the maximum output power and Vmp is the output voltage corresponding to the maximum output power.

[0126] As can be seen from the above formula, the slope K of the PV curve is determined by the proportional amplitude k*∫Dr. Therefore, by adjusting the proportional amplitude of the proportional circuit 302, the slope of the PV curve can be adjusted to ensure that the system achieves maximum power point tracking (MPPT), avoids excessive voltage drop in the inverter input voltage, which would reduce the efficiency of the optimizer and inverter, and further cause power generation loss.

[0127] Regarding adjustment module 3, please refer to other preferred embodiments. Figure 7 The adjustment module 3 further includes a first comparator 306; the non-inverting input terminal of the first comparator 306 is connected to the output terminal of the integrator circuit 301, the inverting input terminal of the first comparator 306 is connected to a reference voltage terminal for inputting a second reference voltage, and the output terminal of the first comparator 306 is connected to the input terminal of the proportional circuit 302.

[0128] The first comparator 306 is configured to compare the integral coefficient ∫Dr with the second reference voltage to output a first signal or a second signal.

[0129] Specifically, the first comparator 306 is further configured as follows:

[0130] When the integral coefficient ∫Dr is above the second reference voltage, the first comparator 306 outputs a first signal;

[0131] When the integral coefficient ∫Dr is less than the second reference voltage, the first comparator 306 outputs a second signal.

[0132] Regarding the working process of the self - calibrating photovoltaic optimizer described in the above solution, in a specific embodiment, the sampling module 2 respectively detects the output voltage and output current, and after multiplication, the output power Pout is obtained; the drive Dr of the free - wheeling diode of the buck circuit (i.e., the converter module 1) passes through the integration circuit 301 to obtain ∫Dr proportional to the drive duty cycle; by setting the integration parameters, if Dr = 1, then ∫Dr = ∫1 = 1; then ∫Dr is sent to the positive input terminal of the first comparator 306, and the reference voltage (i.e., the second reference voltage) Vref is input to the negative input terminal of the first comparator 306; when ∫Dr < Vref, the output of the first comparator 306 is 0, and when ∫Dr > Vref, the output of the first comparator 306 is Vh; the output of the first comparator 306 is connected to the proportional circuit 302, and the proportional circuit 302 outputs k*Vh (the first signal) or outputs 0 (the second signal), and then the output of the proportional circuit 302 is subtracted from the output power Pout and output to the MPPT control module 304; the output of the MPPT adjustment module 3 is the input voltage reference Vin_ref (i.e., the first reference voltage), the input voltage reference Vin_ref (i.e., the first reference voltage) is subtracted from the input voltage Vin and output to the PID control unit 401, and the PID control unit 401 outputs a drive signal obtained by intersecting with the input waveform, which is amplified by the drive circuit and then drives the two switching tubes of the buck circuit (i.e., the converter module 1).

[0133] Specifically, please refer to Figure 9 , Figure 9 as the working PV curve of the self - calibrating photovoltaic optimizer. As can be seen from the figure, adjusting Vref (i.e., the second reference voltage) can adjust the step point of the corrected PV curve, and adjusting the coefficient k of the proportional circuit 302 can adjust the step value of the corrected PV curve; as shown in the figure, the step point is characterized as the point where the PV curve starts to decline as a whole to the left of the maximum power point M; the step value is characterized as the difference between the ordinate after the step point drops and the ordinate of the maximum power point M.

[0134] In one embodiment, please continue to refer to Figure 9 , when Dr is 0, the abscissa Vmp(1 - Dr) of the step point is Vmp, that is, the step point is the maximum power point M, thus realizing the step of the PV curve to the left of the maximum power point M, and the inverter can also judge the maximum power point M according to the stepped PV curve.

[0135] Specifically, adjusting Vref (i.e., the second reference voltage) can adjust the step point, and the step point is Vmp(1 - Dr), where Dr satisfies ∫Dr = Vref; adjusting the coefficient k of the proportional circuit 302 can adjust the step value, and the step value is k*Vh (the first signal). In an example, Vh is the high - level output of the comparator.

[0136] In the above scheme, the corrected PV curve has a step, which can prevent the inverter from stepping down below the step point, that is, prevent the inverter input voltage from being lower than Vmp(1-Dr), where ∫Dr=Vref, which limits the inverter step-down range and avoids low conversion efficiency of the optimizer and inverter, resulting in power generation loss.

[0137] Please refer to Figure 12 The present invention provides a photovoltaic system, comprising: a plurality of photovoltaic modules, an inverter, a power grid, and the self-calibrating photovoltaic optimizer described above;

[0138] The photovoltaic modules are connected in series, and the output terminals of the photovoltaic modules are connected to the input terminals of the self-calibrating photovoltaic optimizers. The output terminals of the self-calibrating photovoltaic optimizers are connected to the input terminals of the inverter, and the output terminals of the inverter are connected to the power grid.

[0139] In a specific embodiment, the inverter can determine the maximum power point based on the PV operating curve of the self-calibrating photovoltaic optimizer, and set the operating voltage to the voltage corresponding to the maximum power point, thereby improving the power generation of the photovoltaic system.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A self-calibrating photovoltaic optimizer, characterized in that, include: The converter module, regulation module, drive module, and sampling module; The converter module has a first terminal connected to an input voltage terminal, a second terminal connected to the input terminal of the sampling module, an output terminal connected to the first terminal of the adjustment module, a second terminal connected to the input voltage terminal, a third terminal connected to the input terminal of the drive module, a first output terminal connected to the fourth terminal of the adjustment module, a second output terminal connected to the third terminal of the converter module, and a second terminal also connected to an output voltage terminal for outputting the operating voltage. The sampling module is configured to: sample the output voltage and output current in real time, and output the current output power; The adjustment module is configured to: determine the maximum output power based on the current output power, and output a first reference voltage; the first reference voltage represents the input voltage corresponding to the maximum output power; The drive module is configured to output a drive signal to the converter module based on the first reference voltage; The converter module is configured to be controlled by the drive signal and output the operating voltage based on the drive signal. The adjustment module includes an integral circuit, a proportional circuit, a first adder, an MPPT control module, and a second adder. Wherein, the first output terminal of the driving module is connected to the input terminal of the integrator circuit, the output terminal of the integrator circuit is connected to the input terminal of the proportional circuit, the output terminal of the proportional circuit is connected to the first terminal of the first adder, the second terminal of the first adder is connected to the input terminal of the MPPT control module, the third terminal of the first adder is connected to the output terminal of the sampling module, the output terminal of the MPPT control module is connected to the first terminal of the second adder, the second terminal of the second adder is connected to the input terminal of the driving module, and the third terminal of the second adder is connected to the input voltage terminal; The integrator circuit is configured to: set an integral coefficient ∫Dr for the first drive signal output by the drive module, and output the integral coefficient ∫Dr to the proportional circuit; The proportional circuit is configured to: perform proportional operation on the integral coefficient ∫Dr by adjusting the proportional coefficient K, so as to output a first proportional amplitude K*∫Dr to the first adder; The first adder is configured to: take the difference between the first proportional amplitude K*∫Dr and the current output power, and output the first difference value to the MPPT control module; The MPPT control module is configured to output the first reference voltage to the second adder based on the first difference. The second adder is configured to take the difference between the first reference voltage and the input voltage, and output a second difference value to the drive module.

2. The self-calibrating photovoltaic optimizer according to claim 1, characterized in that, The adjustment module further includes a first comparator; the non-inverting input of the first comparator is connected to the output of the integrator circuit, the inverting input of the first comparator is connected to a reference voltage terminal for inputting a second reference voltage, and the output of the first comparator is connected to the input of the proportional circuit. The first comparator is configured to compare the integral coefficient ∫Dr with the second reference voltage to output a first signal or a second signal.

3. The self-calibrating photovoltaic optimizer according to claim 2, characterized in that, The first comparator is also configured to: When the integral coefficient ∫Dr is above the second reference voltage, the first comparator outputs a first signal; When the integral coefficient ∫Dr is less than the second reference voltage, the first comparator outputs a second signal.

4. The self-calibrating photovoltaic optimizer according to claim 3, characterized in that, The proportional circuit is also configured to: When the input signal is the first signal, the proportional circuit outputs a second proportional amplitude. When the input signal is the second signal, the proportional circuit outputs a third proportional amplitude.

5. The self-calibrating photovoltaic optimizer according to claim 4, characterized in that, The sampling module includes: a current sampling unit, a voltage sampling unit, and a multiplier; The input terminals of the current sampling unit and the voltage sampling unit are both connected to the converter module, the output terminals of the current sampling unit and the voltage sampling unit are both connected to the first terminal and the second terminal of the multiplier, and the third terminal of the multiplier is connected to the first adder. The multiplier is configured to multiply the output voltage and the output current to output the current output power.

6. The self-calibrating photovoltaic optimizer according to claim 5, characterized in that, The drive module includes: a PID control unit, a second comparator, and a driver; Wherein, the input terminal of the PID control unit is connected to the first terminal of the second adder, the output terminal of the PID control unit is connected to the non-inverting input terminal of the second comparator, the inverting input terminal of the second comparator is connected to an input waveform terminal for inputting an input waveform, the output terminal of the second comparator is connected to the input terminal of the driver, the first output terminal of the driver is connected to the input terminal of the integrator circuit, and the second output terminal of the driver is connected to the third terminal of the converter module; The PID control unit is configured to control the second difference to tend towards infinitesimal and output a PID output value to the non-inverting input of the second comparator; The second comparator is configured to intersect the PID output value with the input waveform to output a second drive signal and a third drive signal; The driver is configured to amplify the second drive signal and the third drive signal to drive the converter module.

7. The self-calibrating photovoltaic optimizer according to claim 6, characterized in that, The converter module includes: a first switching transistor, a second switching transistor, an inductor, a first capacitor, and a second capacitor; Wherein, the control terminal of the first switching transistor is connected to the first output terminal of the driver, the first terminal of the first switching transistor is connected to the input voltage terminal, the second output terminal of the first switching transistor is connected to the first terminal of the second switching transistor and the first terminal of the inductor, the second terminal of the second switching transistor is connected to the first terminal of the first capacitor, the second terminal of the inductor is connected to the second terminal of the first capacitor, and the second capacitor is connected in parallel with the first capacitor and the output voltage terminal. The first and second switching transistors are configured to be controlled by the second drive signal and the third drive signal, and to output the operating voltage based on the ratio of the second drive signal and the third drive signal.

8. The self-calibrating photovoltaic optimizer according to claim 7, characterized in that, The converter module includes a BUCK converter or a BUCK-BOOST converter.

9. The self-calibrating photovoltaic optimizer according to claim 7, characterized in that, The first switch and the second switch include NMOS transistors or PMOS transistors.

10. A photovoltaic system, characterized in that, include: A number of photovoltaic modules, inverters, power grids, and a number of self-calibrating photovoltaic optimizers as described in any one of claims 1-9; The photovoltaic modules are connected in series, and the output terminals of the photovoltaic modules are connected to the input terminals of the self-calibrating photovoltaic optimizers. The output terminals of the self-calibrating photovoltaic optimizers are connected to the input terminals of the inverter, and the output terminals of the inverter are connected to the power grid.

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