Photovoltaic optimizers and photovoltaic systems

Abstract

This application provides a photovoltaic optimizer and a photovoltaic system. The photovoltaic optimizer includes a power conversion circuit, a sampling control circuit, and a capacitor charging and discharging circuit. The capacitor charging and discharging circuit includes a target capacitor, a first resistor, and a first switch. The target capacitor is grounded through the first resistor. The sampling control circuit connects the target capacitor and the first resistor in series through the first switch. The sampling control circuit controls the first switch to turn on or off to allow the target capacitor to undergo multiple charging and discharging cycles, and obtains multiple discharge durations of the target capacitor based on the voltage change of the first resistor. It also obtains the sampling voltage of the photovoltaic power generation module corresponding to the minimum discharge duration among the multiple discharge durations as the maximum power point voltage, and controls the switch in the power conversion circuit to turn on or off so that the output voltage of the photovoltaic power generation module reaches the maximum power point voltage. This application can reduce the circuit cost of the photovoltaic optimizer and improve the power generation efficiency of the photovoltaic system.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and more particularly to a photovoltaic optimizer and a photovoltaic system. Background Technology

[0002] Solar energy, as a safe and clean new energy source, has promising applications in the field of new energy power generation. When generating electricity using solar energy, the output characteristics of photovoltaic (PV) modules in a photovoltaic system are affected by light intensity, ambient temperature, and load conditions. Under certain light intensity and ambient temperature, the output power of the PV module varies with the output voltage. When the output voltage of the PV module is at a specific voltage, its output power is at its maximum; at this point, the PV module operates at its maximum power point (MPP). When changes occur in light intensity or ambient temperature, the maximum output power of the PV module may change. Therefore, maximum power point tracking (MPPT) technology can be used to track the current maximum output power of the PV module in real time to improve photoelectric conversion efficiency.

[0003] In unshaded scenarios, the power-voltage characteristic curve of a photovoltaic (PV) module exhibits a single-peak characteristic, and MPPT algorithms such as the perturbation-observation method or incremental conductance method can be used to track the maximum output power of the PV module in real time. However, in actual use of PV systems, the surrounding environment (such as clouds, trees, tall buildings, dust, etc.) may cause uneven light intensity for the PV module, resulting in local shading. In shaded scenarios, MPPT is typically implemented using complex algorithms and powerful microcontroller units (MCUs), making products with MPPT functionality expensive. Summary of the Invention

[0004] This application provides a photovoltaic optimizer and a photovoltaic system, which can reduce the circuit cost of the photovoltaic optimizer and improve the power generation efficiency of the photovoltaic system.

[0005] In a first aspect, embodiments of this application provide a photovoltaic optimizer, including: a power conversion circuit, a sampling control circuit, and a capacitor charging / discharging circuit; the sampling control circuit is used to connect to a photovoltaic power generation module; the capacitor charging / discharging circuit includes a target capacitor, a first resistor, and a first switch, the target capacitor is grounded through the first resistor, and the sampling control circuit connects the series connection point of the target capacitor and the first resistor through the first switch; the power conversion circuit connects the photovoltaic power generation module and the sampling control circuit; the sampling control circuit is used to control the first switch to turn on or off so that the target capacitor can be charged and discharged multiple times, and obtain multiple discharge durations of the target capacitor based on the voltage change of the first resistor, wherein one charge / discharge of the target capacitor corresponds to one discharge duration; the sampling control circuit is also used to obtain the sampling voltage of the photovoltaic power generation module corresponding to the minimum discharge duration among the multiple discharge durations as the maximum power point voltage, and control the switch in the power conversion circuit to turn on or off so that the output voltage of the photovoltaic power generation module reaches the maximum power point voltage. The photovoltaic power generation module can be a photovoltaic array or a photovoltaic module group, a photovoltaic module group can be composed of one or more photovoltaic modules connected in series and parallel, and a photovoltaic module string can be obtained by connecting one or more photovoltaic modules in series. Here, the MPPT algorithm used in the photovoltaic optimizer is derived from algorithms such as the global scan method or an improved global scan method. In the embodiments of this application, components such as capacitors and resistors are used in the photovoltaic optimizer, and the maximum power point voltage is obtained based on the discharge time of the capacitor. When implementing the MPPT function, the use of expensive components such as multipliers can be reduced, thereby reducing circuit costs.

[0006] In one feasible implementation, the sampling control circuit is used to control the first switch to turn on when a first sampling voltage is obtained in the first sampling period, and to charge the target capacitor based on the first sampling voltage. The first sampling period is any one of the multiple sampling periods included in the MPP scan period. The sampling control circuit is also used to control the first switch to turn off when the voltage across the target capacitor reaches a target voltage, so that the target capacitor begins to discharge. The target voltage can be obtained based on the first sampling voltage. In this embodiment, the charging or discharging of the target capacitor is controlled by controlling the on / off state of the first switch, and the charging process of the target capacitor is controlled based on the first sampling voltage so that the output power of the photovoltaic power generation module can be measured using the discharge duration of the target capacitor. This achieves MPPT using simple components, reduces circuit costs, and improves the applicability of the photovoltaic optimizer.

[0007] In one feasible implementation, the capacitor charging and discharging circuit further includes a duration acquisition unit. The input terminal of the duration acquisition unit is connected to the series connection point of the target capacitor and the first resistor, and the output terminal of the duration acquisition unit serves as the output terminal of the capacitor charging and discharging circuit. The sampling control circuit is used to control the duration acquisition unit to obtain the first discharge duration of the target capacitor based on the voltage change of the first resistor when the first sampling voltage is obtained and the first switch is turned off for the first time. The first discharge duration corresponds to the first sampling voltage. In this embodiment, the sampling control circuit controls the duration acquisition unit to obtain the discharge duration of the target capacitor based on the voltage change of the first resistor, so that the discharge duration can be used to measure the output power of the photovoltaic power generation module, thereby obtaining the maximum power point voltage (MPPT). This can reduce circuit costs and improve system power generation efficiency while achieving MPPT.

[0008] In one feasible implementation, the duration acquisition unit includes a first comparator and a first counter. The non-inverting input of the first comparator is connected to the series connection point of the target capacitor and the first resistor. The inverting input of the first comparator is connected to a sampling control circuit. The output of the first comparator is connected to the input of the first counter, and the output of the first counter serves as the output of the duration acquisition unit. The sampling control circuit, after obtaining a first sampling voltage and the first switch being turned off, controls the first comparator to output a first-level signal to the first counter based on the voltage change of the first resistor. This first-level signal may include a low level or a high level. The sampling control circuit is also used to control the first counter to start counting when the first sampling voltage is obtained and the first switch is turned off for the first time, and to control the first counter to stop counting when the received first-level signal undergoes a transition, obtaining a first count value as the first discharge duration. Here, the first comparator can be an analog comparator. In this embodiment, the sampling control circuit in the photovoltaic optimizer controls the first comparator and the first counter in the capacitor charging and discharging circuit to work together. The first discharge duration is obtained through the first comparator and the first counter. The first discharge duration can be used to indirectly measure the first output power related to the first sampling current and the first sampling voltage. The components used in this photovoltaic optimizer are simple, which can reduce circuit costs and has high applicability.

[0009] In one feasible implementation, the capacitor charging and discharging circuit further includes a second resistor, and the sampling control circuit is grounded through the second resistor. The sampling control circuit is used to control a first comparator to output a first level signal to a first counter after obtaining a first sampling current in the first sampling period and after the first switch is turned off. This first level signal is a level signal obtained by the first comparator comparing the voltage of the first resistor and the voltage of the second resistor. In this embodiment, by comparing the voltage of the first resistor and the voltage of the second resistor, it can be determined whether the target capacitor has discharged to a certain extent. This allows the first counter to determine when to stop counting based on whether the first level signal changes, obtaining a more accurate count value as the first discharge duration, thus ensuring the accuracy of the first discharge duration data.

[0010] In one feasible implementation, the capacitor charging and discharging circuit further includes a first amplifier. The inverting input of the first amplifier is connected to the sampling control circuit, and the output of the first amplifier is connected to the series connection point of the target capacitor and the first resistor via a first switch. Here, the first amplifier can be an inverting amplifier. In this embodiment, using an inverting amplifier to apply the sampling voltage before outputting it to charge the target capacitor helps improve the stability of the circuit.

[0011] In one feasible implementation, the photovoltaic optimizer further includes a comparator circuit, the input of which is connected to the output of the capacitor charging and discharging circuit. The sampling control circuit is used to control the comparator circuit to obtain the sampling voltage of the photovoltaic power generation module corresponding to the minimum discharge duration among multiple discharge durations as the maximum power point voltage. In this embodiment, the comparator circuit, the capacitor charging and discharging circuit, and the sampling control circuit work together to obtain the maximum power point voltage, i.e., to obtain the maximum power point of the photovoltaic power generation module. This is beneficial for the photovoltaic optimizer to achieve the MPPT function and improve the power generation efficiency of the photovoltaic system.

[0012] In one feasible implementation, the comparison circuit includes a comparison output unit and a synchronization unit. The input terminal of the comparison output unit is connected to the output terminal of the duration acquisition unit, and the output terminal of the comparison output unit is connected to the input terminal of the synchronization unit. The sampling control unit controls the comparison output unit to obtain and store the target discharge duration based on M discharge durations output by the first counter. These M discharge durations correspond to the sampling voltages obtained in the current sampling period and the sampling periods before the current sampling period, respectively. M is an integer greater than or equal to 1, and the target discharge duration is the minimum value among the M discharge durations. The sampling control unit controls the synchronization unit to obtain the sampling voltage of the photovoltaic power generation module corresponding to the minimum discharge duration as the maximum power point voltage based on the target discharge duration. In this embodiment, the sampling control circuit, the comparison output unit, and the synchronization unit work together to obtain the maximum power point voltage based on multiple discharge durations output by the capacitor charging and discharging circuit to achieve MPPT, which is beneficial to improving the applicability of the photovoltaic optimizer and improving the power generation efficiency of the photovoltaic system.

[0013] In one feasible implementation, the comparison output unit includes a second comparator and a first register. The two inputs of the second comparator are respectively connected to the output of the first counter and the output of the first register. The output of the second comparator is connected to the enable terminal of the first register, and the data input of the first register is connected to the output of the first counter. The sampling control circuit controls the second comparator to compare the second discharge duration output by the first counter with the target discharge duration stored in the first register to obtain a comparison signal, and controls the second comparator to output the comparison signal to the first register. This comparison signal controls the first register to store the smaller value between the target discharge duration and the second discharge duration as the updated target discharge duration. The second discharge duration is any one of M discharge durations. The sampling control circuit controls the first register to store the updated target discharge duration. The sampling control circuit also controls the second comparator to output the comparison signal to the synchronization unit. Here, the second comparator can be a digital comparator. In this embodiment, the sampling control circuit controls the second comparator to compare the discharge durations corresponding to the sampled voltages obtained in different sampling periods within the MPP scan cycle to obtain a comparison signal. This comparison signal causes the first register to store the real-time minimum discharge duration, thus obtaining the minimum value among all discharge durations in the MPP scan cycle. Controlling the second comparator to output the comparison signal to the synchronization unit enables the synchronization unit to obtain the sampled voltage corresponding to the minimum discharge duration, thereby obtaining the maximum power point voltage. In this way, while obtaining the minimum discharge duration, the synchronization unit can simultaneously obtain the maximum power point voltage, thereby realizing the MPPT function and improving the power generation efficiency of the photovoltaic system.

[0014] In one feasible implementation, the synchronization unit includes a second counter and a second register. The enable terminal of the second register is connected to the output terminal of a second comparator, and the data input terminal of the second register is connected to the output terminal of the second counter. The output terminal of the second register serves as the output terminal of the synchronization unit. A sampling control circuit controls the second counter to calculate the number of sampling periods for the sampling voltage and sampling current of the photovoltaic power generation module and outputs the number of sampling periods to the second register. The sampling control circuit also controls the second register to store the number of sampling periods output by the second counter as a target value when the received comparison signal is a first comparison signal. The first comparison signal indicates a change in the target discharge duration stored in the first register. Furthermore, the sampling control circuit controls the second register to obtain the maximum power point voltage when the number of sampling periods output by the second counter equals the maximum number of sampling periods. This maximum power point voltage is obtained based on the target value stored in the second register and the scan step size. In this embodiment, by controlling the second counter and the second register in the synchronization unit to work collaboratively, the maximum power point voltage can be obtained synchronously when the comparison output unit obtains the globally minimum target discharge duration. This enables the photovoltaic optimizer to achieve the MPPT function, reducing the circuit cost of the photovoltaic optimizer and improving its applicability.

[0015] In one feasible implementation, the power conversion circuit in the photovoltaic optimizer includes a DC-DC converter circuit. The aforementioned sampling control circuit can be used to generate a drive control signal based on the maximum power point voltage output by the comparator circuit and the real-time sampled voltage of the photovoltaic power generation module. Based on this drive control signal, the power switch in the DC-DC converter circuit is controlled to turn on or off, so that the output voltage of the photovoltaic power generation module reaches the maximum power point voltage. In this embodiment, the photovoltaic optimizer can implement the MPPT function, allowing the photovoltaic power generation module to operate at the global maximum power point as much as possible, thereby improving the power generation efficiency of the photovoltaic power generation system. The circuit structure of this photovoltaic optimizer is simple, and while ensuring the implementation of the MPPT function, it can reduce circuit costs, improve the applicability of the photovoltaic optimizer, and improve the power generation efficiency of the photovoltaic system.

[0016] Secondly, this application also provides a photovoltaic system, which includes an inverter and a photovoltaic optimizer as described in the first aspect and any feasible implementation thereof. The input terminal of the photovoltaic optimizer is connected to a photovoltaic power generation module, and the output terminal of the photovoltaic optimizer is connected to the input terminal of the inverter. The output terminal of the inverter is connected to a load, including an AC load. The inverter receives the DC power output from the photovoltaic optimizer and converts the DC power into AC power to supply power to the load. In the embodiments of this application, the photovoltaic optimizer in this photovoltaic system utilizes a simple circuit structure to implement the MPPT function, which can reduce circuit costs, improve the applicability of the photovoltaic optimizer, and improve the power generation efficiency of the photovoltaic system.

[0017] Thirdly, this application also provides a photovoltaic system, which includes a DC-DC converter and a photovoltaic optimizer as described in the first aspect and any feasible implementation thereof. The input terminal of the photovoltaic optimizer is connected to a photovoltaic power generation module, and the output terminal of the photovoltaic optimizer is connected to the input terminal of the DC-DC converter. The output terminal of the DC-DC converter is connected to a load, including a DC load. The DC-DC converter receives the DC power output from the photovoltaic optimizer and performs power conversion on the DC power before outputting it to the load. In the embodiments of this application, the photovoltaic optimizer in this photovoltaic system utilizes a simple circuit structure to implement the MPPT function, which can reduce circuit costs, improve the applicability of the photovoltaic optimizer, and improve the power generation efficiency of the photovoltaic system. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an application scenario of the photovoltaic system provided in the embodiments of this application;

[0019] Figure 2 This is a schematic diagram of the structure of a photovoltaic system provided in an embodiment of this application;

[0020] Figure 3 This is another structural schematic diagram of the photovoltaic system provided in the embodiments of this application;

[0021] Figure 4 This is a schematic diagram of the structure of the photovoltaic optimizer provided in an embodiment of this application;

[0022] Figure 5 This is a flowchart of an MPPT algorithm;

[0023] Figure 6 This is another structural schematic diagram of the photovoltaic optimizer provided in the embodiments of this application;

[0024] Figure 7 This is a U curve diagram of the discharge process of the target capacitor provided in the embodiments of this application;

[0025] Figure 8 This is another structural schematic diagram of the photovoltaic optimizer provided in the embodiments of this application;

[0026] Figure 9 This is another structural schematic diagram of the photovoltaic optimizer provided in the embodiments of this application;

[0027] Figure 10 This is another structural schematic diagram of the photovoltaic optimizer provided in the embodiments of this application. Detailed Implementation

[0028] Solar energy boasts advantages such as abundant resources, long lifespan, wide distribution, safety, cleanliness, and reliable technology. It can be converted into various other forms of energy, thus its applications are very broad. Solar energy can directly convert light energy into electrical energy without a thermal process. This power generation method (referred to as photovoltaic power generation) features no moving parts, no noise, no pollution, and high reliability, making it a promising candidate for new energy power generation. The photovoltaic system provided in this application embodiment can be based on solar photovoltaic power generation and is suitable for powering base station equipment in remote areas without mains power or with poor mains power, or for powering battery-powered devices, or for powering various types of electrical appliances such as household appliances (e.g., refrigerators, air conditioners, etc.) on the AC grid. The specific application scenario can be determined accordingly and is not limited here. See also Figure 1 , Figure 1 This is a schematic diagram of an application scenario of the photovoltaic system provided in an embodiment of this application. For example... Figure 1 The photovoltaic system may include a photovoltaic optimizer and a power converter. The photovoltaic optimizer can be connected to photovoltaic power generation modules and has MPPT (Maximum Power Point Tracking) functionality to enable the photovoltaic power generation modules to operate at their maximum power point, thereby increasing the power generation of the photovoltaic system. The photovoltaic optimizer can be connected to a load through the power converter. Understandably, in some scenarios, the photovoltaic system may also include photovoltaic power generation modules, and this application does not limit this. In this photovoltaic system, the photovoltaic power generation modules can convert solar energy into direct current (DC) energy through the photovoltaic effect. The photovoltaic optimizer can perform maximum power point tracking on the photovoltaic power generation modules, enabling them to maintain a high output power. The DC power output from the photovoltaic power generation modules is then output to the power converter after passing through the photovoltaic optimizer. The power converter can perform power conversion on the DC power and supply power to the load. Here, the power converter may include an inverter or a DC-DC converter, etc. The inverter can convert the DC power into alternating current (AC) to supply power to the load, which may include AC loads such as communication base stations in the AC power grid or household appliances. A DC-DC converter can transform the DC power into another type of DC power that meets the load's requirements to power the load, which may include DC loads such as batteries. The photovoltaic optimizer in this photovoltaic system utilizes MPPT to enable the photovoltaic system to operate at global MPP, improving power generation efficiency.

[0029] The following will combine Figures 2 to 9 The photovoltaic system and photovoltaic optimizer provided in the embodiments of this application are illustrated by example.

[0030] See Figure 2 , Figure 2This is a schematic diagram of a photovoltaic system provided in an embodiment of this application. The photovoltaic system may include a photovoltaic optimizer (also called a photovoltaic adapter or converter) and a power converter. In this photovoltaic system, the photovoltaic optimizer is used to connect photovoltaic power generation components. The photovoltaic power generation components can be photovoltaic arrays or photovoltaic module groups. A photovoltaic module group can be composed of one or more photovoltaic modules connected in series and parallel, and a photovoltaic string can be obtained by connecting one or more photovoltaic modules in series. Here, photovoltaic components can also be called solar cell modules. In other words, the aforementioned photovoltaic power generation components can be composed of all photovoltaic modules in a solar panel connected in series and parallel, or they can be composed of some photovoltaic modules in a solar panel connected in series and / or parallel. Optionally, the photovoltaic system provided in this embodiment may also include photovoltaic power generation components; in other words, in… Figure 2 In the photovoltaic system shown, the photovoltaic array can be connected as needed in actual application scenarios. For ease of description, it will be referred to below as... Figure 2 The photovoltaic system shown is used as an example for illustration, and will not be repeated here. Figure 2 In the photovoltaic system shown, a photovoltaic optimizer can be connected to photovoltaic power generation modules. The optimizer can adjust its output voltage and / or output current to a target voltage or target current based on the output voltage and / or current of the photovoltaic power generation modules and the input voltage and / or input current requirements of the load, and supply power to the load based on the target voltage or target current. That is, in... Figure 2 In the photovoltaic system shown, the photovoltaic optimizer can convert the output voltage of the photovoltaic power generation modules into a target voltage. Furthermore, the photovoltaic optimizer has MPPT (Multi-Level Testing) functionality. In other words, the photovoltaic optimizer can detect the output voltage of the photovoltaic power generation modules in real time and track the output current and output voltage corresponding to the operating point with the highest output power, so that the photovoltaic system outputs electrical energy at maximum power. This electrical energy, after power conversion by the power converter, can supply power to the load, improving the system's power supply efficiency. The power converter in this photovoltaic system can include an inverter or a DC-DC converter, depending on the actual application scenario, and is not limited here. The specific type of load connected to the power converter is related to the power converter; the load can be an AC load or a DC load. When the power converter in the photovoltaic system is an inverter, it can be connected to an AC load; when the power converter in the photovoltaic system is a DC-DC converter, it can be connected to a DC load. In one feasible implementation, in such a way... Figure 2 In the photovoltaic system shown, there can be multiple photovoltaic optimizers, each connected to one photovoltaic power generation module. The outputs of multiple photovoltaic optimizers are connected in parallel to a power converter. When the cost of photovoltaic optimizers is low, this photovoltaic system can be equipped with one photovoltaic optimizer for each of the multiple photovoltaic power generation modules, so that the output power of each photovoltaic power generation module reaches its maximum output power, thereby improving the system's power generation efficiency.

[0031] See Figure 3 , Figure 3 This is another structural schematic diagram of the photovoltaic system provided in the embodiments of this application. For example... Figure 3 As shown, a photovoltaic system may include a photovoltaic optimizer, through which photovoltaic power generation modules are connected to a load. Here, the photovoltaic power generation modules may include one or more photovoltaic modules, which may be a single solar panel or a portion thereof. Figure 3 In the photovoltaic system shown, the DC power output from the photovoltaic modules is directly supplied to the load after passing through a photovoltaic optimizer. This load can include a battery or other DC loads. The photovoltaic optimizer converts the output voltage of the photovoltaic modules to a target voltage and has MPPT (Maximum Power Point Voltage) functionality. In other words, the photovoltaic optimizer can detect the output voltage of the photovoltaic modules in real time and track the output voltage corresponding to the maximum power output (i.e., the maximum power point voltage), enabling the photovoltaic system to supply power to the load at maximum power output. Figure 3 In the photovoltaic system shown, there can be multiple photovoltaic optimizers. Each photovoltaic optimizer can perform MPPT on the photovoltaic power generation module connected to it, so that the photovoltaic power generation module works at the maximum power point as much as possible, thereby improving the system's power generation efficiency.

[0032] In such Figures 1-3 In the photovoltaic system shown, a photovoltaic optimizer with MPPT functionality is used to track the global maximum power point (GMP) of the photovoltaic modules. In unshaded scenarios, the power-voltage characteristic curve of the photovoltaic modules exhibits a single-peak characteristic, and the GMP corresponds to this single peak. Therefore, MPPT algorithms such as the perturbation-observation method or the incremental conductance method can be used to track the maximum output power of the photovoltaic modules in real time. However, in actual use of photovoltaic systems, the surrounding environment (such as clouds, trees, tall buildings, dust, etc.) may cause uneven light intensity on the photovoltaic modules, resulting in localized shading. In this case, the power-voltage characteristic curve of the photovoltaic modules will exhibit multiple peak characteristics, and the GMP corresponds to the largest peak among these multiple peaks. Therefore, the algorithm for implementing MPPT is more complex. In other words, in shaded scenarios, complex algorithms and powerful MCU chips are generally required to implement MPPT. In this case, devices or products with MPPT functionality (such as photovoltaic optimizers) have high circuit costs, limited applicability, and cannot effectively improve the power generation of the photovoltaic system.

[0033] The photovoltaic optimizer provided in this application embodiment can use simple components such as switches, resistors, and capacitors. By controlling the switch to discharge the capacitor, the discharge duration of the capacitor is obtained. This discharge duration is used to measure the output power of the photovoltaic power generation module. Based on these multiple discharge durations, the maximum power point voltage (MPPT) of the photovoltaic power generation module is obtained, thereby controlling the photovoltaic power generation module to operate at its maximum power point. This photovoltaic optimizer can implement MPPT functionality and has low circuit cost, which is beneficial for expanding the application scenarios of photovoltaic optimizers, improving applicability, and increasing the power generation efficiency of photovoltaic systems.

[0034] See Figure 4 , Figure 4 This is a schematic diagram of a photovoltaic optimizer provided in an embodiment of this application. This photovoltaic optimizer can be applied to, for example... Figures 1-3 The photovoltaic system shown. Figure 4 The photovoltaic optimizer shown is applied to, for example Figure 2 The photovoltaic system shown is an example. Figure 4 As shown, the photovoltaic optimizer may include a power conversion circuit, a sampling control circuit, and a capacitor charging / discharging circuit. The sampling control circuit is used to connect to the photovoltaic power generation module, and the power conversion circuit connects the photovoltaic power generation module and the sampling control circuit. Here, the capacitor charging / discharging circuit may include a first switch (i.e., Figure 4 The switch K in the middle), the target capacitor (i.e. Figure 4 The capacitor C) and the first resistor (i.e. Figure 4 The target capacitor is connected to ground via a first resistor (R1 in the circuit). The sampling control circuit connects the target capacitor and the first resistor in series via a first switch. In some embodiments, the capacitor charging / discharging circuit may further include a power supply connected to the other end of the target capacitor to provide energy and ensure subsequent charging and discharging of the capacitor.

[0035] In some feasible implementations, the above-mentioned sampling control circuit can be used to control the first switch to turn on or off to allow the target capacitor to undergo multiple charge-discharge cycles, and to obtain multiple discharge durations of the target capacitor based on the voltage change of the first resistor. Each charge-discharge cycle of the target capacitor corresponds to one discharge duration. The charge-discharge process of the target capacitor each time is related to the sampling voltage and sampling current of the photovoltaic power generation module obtained in the current sampling period. This sampling control circuit can also be used to obtain the sampling voltage of the photovoltaic power generation module corresponding to the minimum discharge duration among the multiple discharge durations of the target capacitor, as the maximum power point voltage of the photovoltaic module, and control the switching transistor in the power conversion circuit to turn on or off so that the output voltage of the photovoltaic power generation module reaches the maximum power point voltage. In other words, the MPPT algorithm used in the photovoltaic optimizer provided in this application is: controlling the first switch to turn on or off to allow the target capacitor to undergo multiple charge-discharge cycles, obtaining multiple discharge durations, and obtaining the maximum power point voltage of the photovoltaic power generation module based on these multiple discharge durations. This MPPT algorithm is derived from algorithms such as the global scan method or an improved global scan method. See also... Figure 5 , Figure 5 This is a flowchart illustrating the MPPT algorithm. (Example) Figure 5 As shown, the MPPT algorithm can be a global scan method, which includes the following steps: Step 501, obtain the current sampled voltage of the photovoltaic power generation module and the output power corresponding to the current sampled voltage. The current sampled voltage is the current sampled value of the output voltage of the photovoltaic power generation module during the MPP scan cycle. This current sampled voltage increases gradually based on a preset scan step size, and the output power corresponding to the current sampled voltage can be obtained based on the current sampled voltage and the current sampled current; Step 502, determine whether the output power corresponding to the current sampled voltage is greater than the stored maximum output power. If yes, proceed to step 503; otherwise, proceed to step 504; Step 503, use the output power corresponding to the current sampled voltage as the updated maximum output power and store it; Step 504, determine whether the current sampled voltage is the maximum scan voltage. The maximum scan voltage refers to the maximum value of the output voltage during the process of controlling the output voltage change of the photovoltaic power generation module based on a preset scan step size. If yes, proceed to step 505; otherwise, return to step 501; Step 505, output the sampled voltage corresponding to the stored maximum output power, which is the maximum power point voltage. In other words, during the process of obtaining MPP using the global scanning method, a product device with MPPT function (such as a photovoltaic optimizer) obtains the PU curve of the photovoltaic power generation module by scanning during the MPP scanning cycle, and obtains the maximum power point voltage corresponding to the global maximum power based on the PU curve, so as to realize the real-time tracking of the global MPP of the photovoltaic power generation module.

[0036] In the embodiments of this application, such as Figure 4The sampling control circuit in the photovoltaic optimizer shown controls the first switch in the capacitor charging and discharging circuit to charge and discharge the target capacitor, thereby obtaining the discharge duration of the target capacitor. The discharge duration of the target capacitor is related to the sampling voltage and sampling current and can be used to measure the output power P of the photovoltaic power generation module. The photovoltaic optimizer can obtain multiple discharge durations based on the voltage change of the first resistor. Based on these multiple discharge durations, the sampling voltage of the photovoltaic power generation module corresponding to the shortest discharge duration is obtained as the maximum power point voltage (MPPT). The switching transistor in the power conversion circuit is then controlled to ensure that the output voltage of the photovoltaic power generation module reaches this MPPT voltage, thus achieving MPPT tracking. In this embodiment, the photovoltaic optimizer uses components such as capacitors and resistors, and obtains the MPPT voltage based on the capacitor's discharge duration. This reduces the use of expensive components such as multipliers when implementing the MPPT function, lowering the circuit cost of the photovoltaic optimizer, improving its applicability, and increasing the power generation efficiency of the power system.

[0037] In one feasible implementation, such as Figure 4 In the photovoltaic optimizer shown, the sampling control circuit is connected to the first switch, specifically the voltage sampling unit in the sampling control circuit. Figure 4(Not shown) The voltage sampling unit connects the target capacitor and the first resistor in series via the first switch. It can be used to obtain and output the sampling voltage of the photovoltaic power generation module. The first switch can be used to turn on or off the path between the sampling control circuit and the target capacitor. The sampling control circuit in the photovoltaic optimizer can control the first switch to turn on when the first sampling voltage is obtained in the first sampling period, charging the target capacitor based on the first sampling voltage. The first sampling period is any one of the multiple sampling periods included in the MPP scan period. In this embodiment, during the MPP scan period, the photovoltaic optimizer can scan the output voltage of the photovoltaic power generation module according to a preset scan step size. Therefore, each sampling period included in the MPP scan period corresponds to an output voltage (also called a sampling voltage) of the photovoltaic power generation module, i.e., the first sampling period and the first sampling voltage correspond. When the sampling control circuit obtains the first sampling voltage in the first sampling period, it controls the first switch to turn on to charge the target capacitor based on the first sampling voltage. This allows the first sampling voltage to be correlated with the charging process of the target capacitor, so that the output power corresponding to the first sampling voltage of the photovoltaic power generation module can be measured subsequently using the discharge time of the target capacitor. During the charging process of the target capacitor, the sampling control circuit can also be used to control the first switch to turn off when the voltage across the target capacitor reaches the target voltage, so that the target capacitor begins to discharge. The target voltage can be obtained based on the first sampled voltage. Thus, the charging process and the start of the discharge of the target capacitor can be controlled based on the first sampled voltage. Furthermore, the sampling control circuit can also control the discharge process of the target capacitor based on the first sampled current obtained in the first sampling period to obtain the discharge duration of the target capacitor. This process will be described in detail below.

[0038] See Figure 6 , Figure 6 This is another structural schematic diagram of the photovoltaic optimizer provided in the embodiments of this application. For example... Figure 6 As shown, in Figure 4 The capacitor charging and discharging circuit shown may further include a duration acquisition unit. The input of this duration acquisition unit is connected to the series connection point of the target capacitor and the first resistor, and the output of the duration acquisition unit serves as the output of the capacitor charging and discharging circuit. The sampling control circuit, upon obtaining a first sampling voltage and the first switch being turned off for the first time, controls the duration acquisition unit to obtain the first discharge duration of the target capacitor based on the voltage change of the first resistor. The first discharge duration corresponds to the first sampling voltage. In other words, when the target capacitor charges and discharges, the voltage of the first resistor changes. The sampling control circuit controls the duration acquisition unit to obtain the discharge duration of the target capacitor based on this change, so that this discharge duration can be used to measure the output power of the photovoltaic power generation module, thereby obtaining the maximum power point voltage (MPPT), achieving MPPT, and improving the system's power generation efficiency. This duration acquisition unit may include analog devices and low-cost digital devices.

[0039] In some feasible implementations, such as Figure 6 As shown, the aforementioned duration acquisition unit may include a first comparator (i.e., Figure 6 The comparator COMP1 and the first counter (i.e. Figure 6 The first comparator can be an analog comparator. The non-inverting input of the first comparator is connected to the series connection point of the target capacitor and the first resistor. The inverting input of the first comparator is connected to the sampling control circuit. The output of the first comparator is connected to the input of the first counter, and the output of the first counter serves as the output of the duration acquisition unit. The sampling control circuit can be used to control the first comparator to output a first-level signal to the first counter based on the voltage change of the first resistor after obtaining the first sampling voltage and the first switch being turned off for the first time. This first-level signal includes either a low level or a high level. In other words, when the sampling control circuit has obtained the first sampling voltage and the first switch is turned off for the first time after obtaining the first sampling voltage, the target capacitor begins to discharge, and the first comparator outputs a high or low level based on the voltage change of the first resistor, transmitting this high or low level to the first counter. When the first sampling voltage is obtained and the first switch is turned off for the first time, the sampling control circuit can also control the first counter (e.g., ...). Figure 6 The counter (CNT1) in the photovoltaic optimizer can be used to start counting when the first switch is turned off and stop counting when the received first level signal changes, obtaining a first count value as the first discharge duration. Here, the first discharge duration is the discharge duration experienced by the target capacitor after it has been charged based on the first sampling voltage and discharged to a certain extent (related to the first sampling current). In this way, the sampling control circuit in the photovoltaic optimizer can control the first comparator and the first counter in the capacitor charging and discharging circuit to work together, and obtain the discharge duration corresponding to the first sampling voltage and the first sampling current based on the first sampling voltage and the first sampling current. This realizes the use of the discharge duration to correlate the first sampling voltage and the first sampling current, which is beneficial for obtaining the maximum power point voltage based on the discharge duration, reducing the circuit cost of the photovoltaic optimizer, improving the applicability of the photovoltaic optimizer, and improving the system power generation efficiency.

[0040] In some feasible implementations, the above-mentioned capacitor charging and discharging circuit further includes a second resistor (such as...). Figure 6 R2 in the circuit can be grounded through this second resistor. Specifically, this refers to the current sampling unit in the sampling control circuit. Figure 6(Not shown) Grounded through the second resistor, the current sampling unit can obtain and output the sampled current of the photovoltaic power generation module. In this embodiment, the sampling control circuit can be used to control the first comparator to output a first level signal obtained by comparing the voltage of the first resistor and the voltage of the second resistor to the first counter after obtaining the first sampled current in the first sampling period and the first switch is turned off for the first time. Here, the voltage of the second resistor is related to the resistance value of the second resistor and the first sampled current. Since the first level signal is obtained based on the comparison result of the voltage of the first resistor and the voltage of the second resistor, it can be determined whether the target capacitor has discharged to a certain extent by comparing the voltage of the first resistor and the voltage of the second resistor. Thus, the first counter can determine the timing of stopping counting based on whether the first level signal jumps, and obtain a more accurate count value as the first discharge duration, ensuring the accuracy of the first discharge duration data. In this way, by controlling the charging and discharging of the target capacitor based on the first sampling voltage and the first sampling current, the first discharge duration of the target capacitor can be obtained. The first discharge duration can be used to measure the first output power of the photovoltaic power generation module (the first output power is equal to the product of the first sampling voltage and the first sampling current). This is beneficial for obtaining the maximum power point voltage of the photovoltaic power generation module based on multiple discharge durations, thereby reducing the circuit cost of the photovoltaic optimizer and improving the applicability of the photovoltaic optimizer.

[0041] Understandably, when the first switch is turned off, the target capacitor begins to discharge, and the voltage of the first resistor gradually changes. The first comparator outputs a first-level signal based on the relationship between the voltages of the first and second resistors. During this process, the voltage of the first resistor may remain higher than the voltage of the second resistor, so the first-level signal can remain high. After the target capacitor has discharged for a period of time, the voltage of the first resistor gradually decreases to be equal to or less than the voltage of the second resistor, so the first-level signal changes to a low level. The first counter stops counting when the first-level signal changes, and the count value is used as the first discharge duration. In this way, by using the first comparator and the first counter in the counting unit to obtain the first discharge duration, the first output power related to the first sampling current and the first sampling voltage can be indirectly measured using the first discharge duration. The components used in this photovoltaic optimizer are simple, which can reduce circuit costs and has high applicability.

[0042] In some feasible implementations, such as Figure 6 As shown, Figure 4 The capacitor charging and discharging circuit shown may also include a first amplifier (such as...) Figure 6The amplifier A1 in the circuit is connected to the sampling control circuit via its inverting input, and its output is connected to the series connection point of the target capacitor and the first resistor via a first switch. Specifically, the inverting input of the first amplifier can be connected to the voltage sampling unit of the sampling control circuit to act on the sampled voltage. Here, the first amplifier can be an inverting amplifier used to invert the first sampled voltage and output it to the non-inverting input of the first comparator via the first switch. This allows the inverting amplifier to reverse the sampled voltage before outputting it to charge the target capacitor, which improves circuit stability.

[0043] The following is combined with, for example Figure 6 The structure of the photovoltaic optimizer shown is described in detail, with the first discharge duration t as an example. o With the first sampling voltage u s and the first sampling current i s The relationship.

[0044] When the target capacitor is charged to the target voltage, the voltage u across the target capacitor... C0 satisfy:

[0045] u C0 =Eu s

[0046] During the discharge process of the target capacitor, the voltage u across the target capacitor... C The relationship between discharge duration t and the voltage u at the non-inverting input of the first comparator p and the voltage u at the inverting input of the first comparator n They respectively satisfy:

[0047]

[0048]

[0049] u n =i s *R2

[0050] The first counter starts counting when the first sampling voltage is obtained and the first switch is open; when the voltage at the non-inverting input of the first comparator drops to equal the voltage at the inverting input of the first comparator, the level signal output by the first comparator changes, and the first counter stops counting. The time elapsed from the start of counting to the stop of counting during this round of discharge is the first discharge duration t. o The first discharge duration t o satisfy:

[0051]

[0052] Therefore, the first discharge duration t is obtained.o satisfy:

[0053]

[0054] In formula (2), R1 is the resistance value of the first resistor, R2 is the resistance value of the second resistor, and E is the power supply voltage connected to the target capacitor.

[0055] From the above formula (2), it can be seen that the first discharge duration t o With the first sampling voltage u s There is a negative correlation, and the discharge duration t o Also related to the first sampling current i s If they are negatively correlated, then t o The product of the first sampling voltage and the first sampling current is approximately negatively correlated. Therefore, the output power of the photovoltaic power generation module can be indirectly measured by the length of the discharge duration.

[0056] On the other hand, based on formula (1), it can be seen that during the discharge process of the target capacitor, u C The curve showing how it changes with time t is as follows Figure 7 As shown. Curve 1 represents the first sampled voltage u. s Minimum sampling voltage u smin u at time C -t curve, curve 2 is the first sampling voltage u s For the maximum sampling voltage u smax u at time C The -t curves show examples of larger and smaller first sampling currents, I1 and I2, respectively. Figure 7 It can be seen that when the first sampling voltage and the first sampling current are both large, such as at point A, the first discharge duration of the target capacitor is short; when the first sampling voltage and the first sampling current are both small, such as at point B, the first discharge duration of the target capacitor is long; and when the first sampling voltage and the first sampling current are both large, such as at point C, the first discharge duration of the target capacitor is short. That is, the relationship between the first discharge duration and the first sampling voltage and the first sampling current is similar to the relationship between the first output power and the first sampling voltage and the first sampling current. Therefore, the first discharge duration can be used to measure the magnitude of the first output power to achieve MPP. This application reduces the circuit cost of the photovoltaic optimizer by replacing high-cost components such as multipliers with components such as resistors and capacitors, thereby improving the applicability of the photovoltaic optimizer and increasing the power generation efficiency of the photovoltaic system.

[0057] See Figure 8 , Figure 8 This is another structural schematic diagram of the photovoltaic optimizer provided in the embodiments of this application. For example... Figure 8 As shown, Figure 4 or Figure 6The photovoltaic optimizer shown may also include a comparator circuit. The input of this comparator circuit is connected to the output of the capacitor charging / discharging circuit. The sampling control circuit in the photovoltaic optimizer can be used to control the comparator circuit to obtain the sampled voltage of the photovoltaic module corresponding to the minimum discharge duration among multiple discharge durations, as the maximum power point voltage. After obtaining the maximum power point voltage, the comparator circuit can output it to the sampling control circuit, so that the sampling control circuit controls the operation of the switching transistors in the power conversion circuit, thereby enabling the photovoltaic module to operate at its maximum power point. The comparator circuit, the capacitor charging / discharging circuit, and the sampling control circuit work together to obtain the maximum power point voltage, i.e., the maximum power point of the photovoltaic module, which helps the photovoltaic optimizer achieve the MPPT function and improve the power generation efficiency of the photovoltaic system.

[0058] In one feasible implementation, such as Figure 9 As shown, Figure 8The comparison circuit shown may include a comparison output unit and a synchronization unit. The input terminal of the comparison output unit can serve as the input terminal of the comparison circuit, connected to the output terminal of the duration acquisition unit. The output terminal of the comparison output unit is connected to the input terminal of the synchronization unit, and the output terminal of the synchronization unit can serve as the output terminal of the comparison circuit. In this comparison circuit, the comparison output unit and the synchronization unit work together to obtain the maximum power point voltage of the photovoltaic power generation module in the MPP scan cycle based on multiple discharge durations. Specifically, the sampling control circuit can control the comparison output unit to obtain and store the target discharge duration based on the M discharge durations output by the first counter, and output the target discharge duration to the synchronization unit. The M discharge durations correspond to the sampled voltages obtained in the current sampling cycle and the sampling cycles preceding the current sampling cycle, respectively, where M is an integer greater than or equal to 1, and the target discharge duration is the minimum value among the aforementioned M discharge durations. That is, the target discharge duration output by the comparison output unit is always the minimum value among the M discharge durations corresponding to the M sampled voltages obtained from the first sampling cycle to the current sampling cycle (the number of sampling cycles is M) in the MPP scan cycle. The comparison output unit consistently outputs the minimum real-time discharge duration as the target discharge duration to the synchronization unit. Correspondingly, the sampling control circuit controls the synchronization unit to obtain the sampling voltage of the photovoltaic module corresponding to the minimum discharge duration based on the target discharge duration, as the maximum power point voltage. Understandably, the maximum power point voltage is the sampling voltage corresponding to the maximum output power obtained in the MPP scan cycle. Therefore, the target discharge duration for obtaining the maximum power point voltage is the minimum value among the discharge durations corresponding to all sampling cycles in that MPP scan cycle. In other words, when M equals the total number of sampling cycles included in the MPP scan cycle (or when the sampling voltage is the maximum scan voltage), the synchronization unit outputs the target discharge duration to the synchronization unit, which can then obtain the maximum power point voltage based on this target discharge duration. Thus, the sampling control circuit controls the comparison output unit to obtain the minimum value (i.e., the minimum discharge duration) among all discharge durations as the target discharge duration, outputs this target discharge duration to the synchronization unit, and controls the synchronization unit to obtain the maximum power point voltage based on this target discharge duration. The sampling control circuit, the comparison output unit, and the synchronization unit work together to obtain the maximum power point voltage based on multiple discharge durations output by the capacitor charging and discharging circuit, thereby achieving MPPT. This is beneficial for improving the applicability of the photovoltaic optimizer and increasing the system's power generation efficiency.

[0059] See Figure 10 , Figure 10 This is another structural schematic diagram of the photovoltaic optimizer provided in the embodiments of this application. For example... Figure 10 As shown, Figure 9 The comparison output unit shown may include a second comparator (such as...) Figure 10The comparator COMP2 and the first register (as shown in the image) Figure 10 The two inputs of the second comparator are connected to the output of the first counter and the output of the first register, respectively. Here, the second comparator can be a digital comparator. The two inputs of the second comparator may include, for example, register REG1. Figure 10 The comparator COMP2 has COMP and COMN terminals. COMN is connected to the output of the first counter, and COMP is connected to the output of the first register. The second comparator operates as follows: when the value received at COMP is greater than the value received at COMN, it outputs a high level (or 1); when the value received at COMP is less than the value received at COMN, it outputs a low level (or 0); when the value received at COMP equals the value received at COMN, it can output a low level, or optionally, a high level. The output of the second comparator is connected to the enable terminal of the first register, and the data input terminal of the first register is connected to the output of the first counter. The enable terminal of the first register can be configured as follows: Figure 10 The data input terminal of the first register at the LOAD terminal of REG1 can be as follows: Figure 10The IN terminal of REG1. The working principle of the first register is as follows: when a high level is received at the LOAD terminal (i.e., the value of the LOAD terminal is 1), the first register writes the data received at the IN terminal and stores it; when a low level is received at the LOAD terminal (i.e., the value of the LOAD terminal is 0), the first register retains its original stored value. In this embodiment, the sampling control circuit can control the second comparator to compare the second discharge duration output by the first counter with the target discharge duration stored in the first register to obtain a comparison signal, and control the second comparator to output the comparison signal to the first register. Here, the second discharge duration is any one of the above M discharge durations. Here, the comparison signal may include a high level or a low level (i.e., 1 or 0). When the second discharge duration output by the first counter is less than the target discharge duration stored in the first register, the comparison signal is high, and the first register can write new data, that is, store the second discharge duration output by the first counter as the updated target discharge duration. When the second discharge duration output by the first counter is greater than the target discharge duration stored in the first register, the comparison signal is low, and the first register can keep the originally stored data unchanged, that is, store the originally stored target discharge duration as the updated target discharge duration. In other words, the comparison signal is used to control the first register to store the smaller value between the target discharge duration and the second discharge duration as the updated target discharge duration. That is, the second comparator is used to compare the discharge duration output by the first counter in real time with the real-time minimum discharge duration stored in the first register (that is, the minimum value among the previously output discharge durations, which is also the target discharge duration), generate a comparison signal, and through the comparison signal, the first register obtains the smaller value between the two as the updated real-time minimum discharge duration (that is, the updated target discharge duration) and stores it. The sampling control circuit is also used to control the first register to store the updated target discharge duration. The sampling control circuit is also used to control the second comparator to output the comparison signal to the synchronization unit. Understandably, when the second discharge duration is the discharge duration corresponding to the sampling voltage obtained in the first sampling cycle of the MPP scan period, the first counter outputs the discharge duration to the first register, and the first register writes the discharge duration as the initial target discharge duration. Thus, when the first counter obtains the discharge duration corresponding to the sampling voltage obtained in the second sampling cycle, the second comparator can compare the output of the first counter with the initial target discharge duration stored in the first register to generate a comparison signal.In this embodiment, the sampling control circuit controls the second comparator to compare the discharge durations corresponding to the sampled voltages obtained in different sampling periods within the MPP scan cycle to obtain a comparison signal. This comparison signal causes the first register to store the real-time minimum discharge duration, thus obtaining the minimum value among all discharge durations in the MPP scan cycle. Controlling the second comparator to output the comparison signal to the synchronization unit enables the synchronization unit to obtain the sampled voltage corresponding to the minimum discharge duration, thereby obtaining the maximum power point voltage. In this way, while obtaining the minimum discharge duration, the synchronization unit can simultaneously obtain the maximum power point voltage, thereby realizing the MPPT function and improving the power generation efficiency of the photovoltaic system.

[0060] In one feasible implementation, such as Figure 9 The synchronization unit shown includes a second counter (such as...) Figure 10 The counter CNT2) and the second register (such as Figure 10 The data input of the second register is connected to the output of the second counter, and the enable input of the second register is connected to the output of the second comparator. The output of the second register serves as the output of this synchronization unit. Here, the enable input of the second register can be as follows: Figure 10 The LOAD pin of REG2 and the data input pin of the second register can be as follows: Figure 10 The IN terminal of REG2. The working principle of the second register is similar to that of the first register, and will not be repeated here. In this embodiment, the sampling control circuit can be used to control the second counter to calculate the number of sampling periods for obtaining the sampling voltage and sampling current of the photovoltaic power generation module, and output the number of sampling periods to the second register. In other words, the second counter is controlled to count the number of sampling periods that the photovoltaic power generation module has sampled in the MPP scan cycle and output the number of sampling periods. Here, the clock signal of the second counter (such as...) Figure 10 CLK2 in the middle) and the clock signal of the first counter (such as Figure 10 CLK1 in the second counter can be a different clock signal. The start signal of the second counter (e.g., ...) Figure 10 The CNT2_Start signal in the first counter (e.g., the start signal of the first counter) is the same as the start signal of the first counter (e.g., the start signal of the first counter). Figure 10The setting time of CNT1_Start can also be different. The sampling control circuit can also be used to control the second register to store the number of sampling periods output by the second counter as the target value when the received comparison signal is the first comparison signal. Here, the first comparison signal is used to indicate that the target discharge duration stored in the first register will change. Specifically, the first comparison signal can be a comparison signal that enables the second register to write new data, such as the first comparison signal can be high level. The second register is also used to output the maximum power point voltage when the number of sampling periods output by the second counter is equal to the maximum number of sampling periods, where the maximum power point voltage is obtained based on the target value stored in the second register and the scan step size. Here, the maximum number of sampling periods refers to the total number of sampling periods included in the MPP scan period. Since the output voltage of the photovoltaic power generation module (i.e., the sampling voltage) changes gradually based on the preset scan step size during the MPP scan period, the current sampling voltage can be obtained based on the number of sampling periods output by the second counter and the scan step size. When the second counter acquires and outputs the number of sampling periods from the first sampling period to the current sampling period in the current MPP scan cycle, the second register can output the maximum power point voltage at the end of the current scan process. The sampling control circuit can control the second register to store the sampling voltage corresponding to the target discharge duration. Here, when the number of sampling periods output by the second counter is the maximum number of sampling periods, the sampling voltage corresponding to the target discharge duration is the output voltage corresponding to the global maximum power point, that is, the maximum power point voltage Umpp. In this way, by controlling the second counter and the second register in the synchronization unit to work together, the maximum power point voltage can be obtained synchronously when the comparison output unit obtains the global minimum target discharge duration, so that the photovoltaic optimizer can realize the MPPT function, which can reduce the circuit cost of the photovoltaic optimizer and improve its applicability.

[0061] In some feasible implementations, the power conversion circuit in the photovoltaic optimizer provided in this application embodiment may include a DC-DC converter circuit. The sampling control circuit in the photovoltaic optimizer can be used to generate a drive control signal based on the maximum power point voltage output by the comparator circuit and the real-time sampled voltage of the photovoltaic power generation module. Based on this drive control signal, it controls the switching transistors in the DC-DC converter circuit to turn on or off, so that the output voltage of the photovoltaic power generation module reaches the maximum power point voltage corresponding to the aforementioned MPP scan cycle. In other words, based on the drive control signal, the power switching transistors in the DC-DC converter circuit can be controlled to operate, so that the output power of the photovoltaic power generation module reaches the maximum power corresponding to the MPP scan cycle. Thus, the photovoltaic optimizer can realize the MPPT function, allowing the photovoltaic power generation module to operate as close to the global maximum power point as possible, thereby improving the power generation efficiency of the photovoltaic power generation system. The circuit structure of this photovoltaic optimizer is simple, ensuring the implementation of the MPPT function while reducing circuit costs, improving the applicability of the photovoltaic optimizer, and increasing the power generation efficiency of the photovoltaic system. It is understood that, on the one hand, the sampling control circuit in the photovoltaic optimizer can control the operation of the capacitor charging and discharging circuit and the comparator circuit to obtain the maximum power point voltage and realize MPPT control. On the other hand, the sampling control circuit can also obtain a drive control signal based on the obtained maximum power point voltage and the real-time sampled voltage of the photovoltaic power generation module, so as to control the operation of the switching transistors in the DC-DC converter circuit to make the photovoltaic power generation module operate at the maximum power point. At this time, the sampling control circuit can realize loop control. In practical applications, both MPPT control and loop control functions can be implemented by the sampling control circuit, or they can be implemented by different modules included in the sampling control circuit. The specific implementation depends on the actual scenario, and this application does not impose any restrictions on this.

[0062] In one possible implementation, the photovoltaic optimizer in the aforementioned photovoltaic system can perform a global scan based on a fixed period to obtain the maximum power and / or maximum power point voltage corresponding to the MPP scan cycle. For example, a global scan is performed every preset time interval t1 to obtain the maximum power point voltage corresponding to that MPP scan cycle. A drive signal is generated based on this maximum power point voltage and the real-time sampled voltage of the photovoltaic power generation module to control the photovoltaic power generation module to operate at the maximum power point corresponding to that MPP scan cycle. Optionally, the photovoltaic optimizer in the aforementioned photovoltaic system can also perform a global scan based on the change in the output power of the photovoltaic power generation module to obtain the maximum power and / or maximum power point voltage corresponding to that MPP scan cycle. For example, when the change value or rate of change of the output power of the photovoltaic power generation module exceeds a preset threshold, the photovoltaic optimizer can be controlled to start a global scan to obtain the maximum power point voltage corresponding to this MPP scan cycle. Optionally, the controller in the aforementioned photovoltaic system can also combine the above two global scan methods or use other methods to determine the timing of starting the global scan, which can be determined according to the actual application scenario, and this application does not impose any restrictions. In one possible implementation, the photovoltaic optimizer can, based on the maximum power point voltage output by the comparator circuit, perform perturbation observation within a voltage range near the maximum power point voltage to obtain a more accurate maximum power point.

[0063] In this embodiment, the sampling control circuit in the photovoltaic optimizer can control the first switch to be turned on or off, causing the target capacitor in the capacitor charging and discharging circuit to undergo multiple charging and discharging cycles. It also obtains multiple discharge durations based on the voltage change of the first resistor. Based on these multiple discharge durations, the sampling voltage corresponding to the shortest discharge duration is obtained as the maximum power point voltage (MPPT). The switching transistor in the power conversion circuit is then controlled to ensure that the output voltage of the photovoltaic power generation module reaches this MPPT. This embodiment utilizes the discharge duration of the target capacitor to measure the output power of the photovoltaic power generation module. Based on this discharge duration, the MPPT voltage is obtained, and the photovoltaic power generation module operates at its maximum power point. This allows the photovoltaic optimizer to achieve the MPPT function using simple components such as resistors and capacitors, reducing the use of expensive components such as multipliers, thereby lowering the circuit cost of the photovoltaic optimizer, improving its applicability, and increasing the power generation efficiency of the photovoltaic system.

Claims

1. A photovoltaic optimizer, characterized by, include: The system includes a power conversion circuit, a sampling control circuit, and a capacitor charging / discharging circuit. The sampling control circuit is used to connect to a photovoltaic power generation module. The capacitor charging / discharging circuit includes a target capacitor, a first resistor, and a first switch. The target capacitor is grounded through the first resistor. The sampling control circuit is connected to the series connection point of the target capacitor and the first resistor through the first switch. The power conversion circuit connects the photovoltaic power generation module and the sampling control circuit. The sampling control circuit is used to control the first switch to be turned on or off so that the target capacitor can be charged and discharged multiple times, and to obtain multiple discharge durations of the target capacitor based on the voltage change of the first resistor, wherein each charge and discharge of the target capacitor corresponds to one discharge duration. The sampling control circuit is also used to obtain the sampling voltage of the photovoltaic power generation module corresponding to the minimum discharge duration among the multiple discharge durations as the maximum power point voltage, and control the switching transistor in the power conversion circuit to turn on or off so that the output voltage of the photovoltaic power generation module reaches the maximum power point voltage.

2. The photovoltaic optimizer of claim 1, wherein, The sampling control circuit is used to control the first switch to turn on when the first sampling voltage is obtained in the first sampling period, and to charge the target capacitor based on the first sampling voltage. The first sampling period is any one of the multiple sampling periods included in the maximum power point (MPP) scanning period. The sampling control circuit is also used to control the first switch to turn off when the voltage across the target capacitor reaches the target voltage, so that the target capacitor begins to discharge, and the target voltage is obtained based on the first sampling voltage.

3. The photovoltaic optimizer of claim 2, wherein, The capacitor charging and discharging circuit further includes a duration acquisition unit. The input terminal of the duration acquisition unit is connected to the series connection point of the target capacitor and the first resistor, and the output terminal of the duration acquisition unit serves as the output terminal of the capacitor charging and discharging circuit. The sampling control circuit is used to control the duration acquisition unit to obtain the first discharge duration of the target capacitor based on the voltage change of the first resistor when the first sampling voltage is obtained and the first switch is turned off for the first time. The first discharge duration corresponds to the first sampling voltage.

4. The photovoltaic optimizer of claim 3, wherein, The duration acquisition unit includes a first comparator and a first counter. The non-inverting input of the first comparator is connected to the series connection point of the target capacitor and the first resistor. The inverting input of the first comparator is connected to the sampling control circuit. The output of the first comparator is connected to the input of the first counter. The output of the first counter serves as the output of the duration acquisition unit. The sampling control circuit is used to control the first comparator to output a first level signal to the first counter based on the voltage change of the first resistor after obtaining the first sampling voltage and the first switch is turned off for the first time. The first level signal includes a low level or a high level. The sampling control circuit is further configured to control the first counter to start counting when the first sampling voltage is obtained and the first switch is turned off for the first time, and control the first counter to stop counting when the first level signal received jumps, and obtain a first count value as the first discharging duration.

5. The photovoltaic optimizer of claim 4, wherein, The capacitor charging and discharging circuit further comprises a second resistor, and the sampling control circuit is grounded through the second resistor. The sampling control circuit is configured to control the first comparator to output the first level signal to the first counter after the first sampling current is obtained in the first sampling period and the first switch is turned off for the first time, the first level signal being a level signal obtained by the first comparator comparing the voltage of the first resistor and the voltage of the second resistor.

6. The photovoltaic optimizer of claim 4, wherein, The capacitor charging and discharging circuit further comprises a first amplifier, an inverting input terminal of the first amplifier being connected to the sampling control circuit, and an output terminal of the first amplifier being connected to a connection point of the target capacitor and the first resistor in series through the first switch.

7. The photovoltaic optimizer according to any of claims 4-6, characterized in that, The photovoltaic optimizer further comprises a comparison circuit, an input terminal of the comparison circuit being connected to an output terminal of the capacitor charging and discharging circuit. The sampling control circuit is configured to control the comparison circuit to obtain, as the maximum power point voltage, a sampling voltage of a photovoltaic power generation component corresponding to a minimum discharging duration in the plurality of discharging durations based on the plurality of discharging durations.

8. The photovoltaic optimizer of claim 7, wherein, The comparison circuit comprises a comparison output unit and a synchronization unit, an input terminal of the comparison output unit being connected to an output terminal of the duration obtaining unit, and an output terminal of the comparison output unit being connected to an input terminal of the synchronization unit; and the sampling control circuit is configured to: control the comparison output unit to obtain a target discharging duration based on M discharging durations output by the first counter and store the target discharging duration, the M discharging durations corresponding to sampling voltages obtained in a current sampling period and sampling periods before the current sampling period respectively, the M being an integer greater than or equal to 1, and the target discharging duration being a minimum value in the M discharging durations; and control the synchronization unit to obtain, as the maximum power point voltage, a sampling voltage of a photovoltaic power generation component corresponding to the minimum discharging duration based on the target discharging duration.

9. The photovoltaic optimizer of claim 8, wherein, The comparison output unit comprises a second comparator and a first register, two input terminals of the second comparator being respectively connected to an output terminal of the first counter and an output terminal of the first register, an output terminal of the second comparator being connected to an enable terminal of the first register, and a data input terminal of the first register being connected to an output terminal of the first counter; and the sampling control circuit is configured to: control the second comparator to compare a second discharging duration output by the first counter with the target discharging duration stored in the first register to obtain a comparison signal, and control the second comparator to output the comparison signal to the first register, the comparison signal being used to control the first register to store a smaller value between the target discharging duration and the second discharging duration as an updated target discharging duration, the second discharging duration being any one of the M discharging durations. The first register is controlled to store the updated target discharging time length; The second comparator is controlled to output the comparison signal to the synchronization unit.

10. The photovoltaic optimizer of claim 9, wherein, The synchronization unit comprises a second counter and a second register, an enable end of the second register is connected to an output end of the second comparator, a data input end of the second register is connected to an output end of the second counter, and an output end of the second register serves as an output end of the synchronization unit; and the sampling control circuit is configured to: The second counter is controlled to calculate a number of sampling periods of a sampling voltage and a sampling current of the photovoltaic power generation component, and the second counter is controlled to output the number of sampling periods to the second register; The second register is controlled to store the number of sampling periods output by the second counter as a target value when the received comparison signal is a first comparison signal, the first comparison signal being used to indicate that the target discharging time length stored by the first register is changed; When the number of sampling periods output by the second counter is equal to a maximum number of sampling periods, the second register is controlled to obtain the maximum power point voltage, the maximum power point voltage being obtained based on the target value stored by the second register and a scanning step length.

11. The photovoltaic optimizer of claim 7, wherein, The power conversion circuit comprises a direct current (DC)-DC conversion circuit; The sampling control circuit is configured to generate a driving control signal based on the maximum power point voltage output by the comparison circuit and a real-time sampling voltage of the photovoltaic power generation component, and control a power switch tube in the DC-DC conversion circuit to be turned on or turned off based on the driving control signal, so that an output voltage of the photovoltaic power generation component reaches the maximum power point voltage.

12. A photovoltaic system characterized by, The photovoltaic system comprises an inverter and the photovoltaic optimizer according to any one of claims 1-11; an input end of the photovoltaic optimizer is configured to be connected to a photovoltaic power generation component, an output end of the photovoltaic optimizer is connected to an input end of the inverter, and an output end of the inverter is configured to be connected to a load; and the load comprises an alternating current (AC) load. The inverter is configured to receive direct current (DC) output by the photovoltaic optimizer, and convert the DC into alternating current (AC) to supply power to the load.

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