Photovoltaic optimizer and control method

Abstract

The present application relates to a photovoltaic optimizer and a control method. In the control method, the power supply is switched between an off mode, a protection mode, and a maximum power point tracking mode by monitoring the magnitude of the input voltage. Thus, when the output power of a photovoltaic module is insufficient due to factors such as shading, maximum power point tracking is not performed in the protection mode. Instead, the duty cycle is adjusted to keep the input voltage greater than a first threshold, thereby maintaining the normal operation of the photovoltaic optimizer. This avoids repeated restarts of the photovoltaic optimizer or severe fluctuations in the output voltage due to power sag or power shortage, thereby improving the stability and reliability of the photovoltaic optimizer.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaics, and in particular to a photovoltaic optimizer and a control method. Background Art

[0002] As a vital component of renewable energy, photovoltaic systems are increasingly valued for their efficiency and stability. PV optimizers monitor and adjust the current and voltage of PV modules in real time, maximizing their efficiency under varying environmental conditions and improving the overall system's power generation. Furthermore, PV optimizers can detect and isolate module-level faults, significantly enhancing system reliability and stability.

[0003] However, PV systems face complex and volatile environmental challenges in actual operation. The power generated by PV modules is significantly affected by sunlight intensity and temperature coefficients. In particular, factors such as sunrise and sunset, weather changes, and random shading can cause significant fluctuations in the module's output power. These fluctuations are often sudden and unpredictable, posing a severe challenge to the proper functioning of PV optimizers. For example, when a PV module's output power drops suddenly, the PV optimizer will rapidly adjust its output voltage and current to maintain the maximum power point. However, this adjustment also causes the PV optimizer's input voltage and current (i.e., the PV module's output voltage and current) to fluctuate rapidly, leading to significant fluctuations in the PV optimizer's output voltage. This can also cause the PV optimizer's input voltage to fall below its startup voltage threshold, causing the optimizer to shut down. This shutdown, in turn, leaves the PV module in an open-circuit state, with zero output current and an output voltage at the open-circuit voltage. This open-circuit voltage is generally greater than the optimizer's startup voltage threshold, forcing the optimizer to restart. Once restarted, it again shuts down to maintain the maximum power point, creating a vicious cycle of repeated restarts.

[0004] Severe fluctuations in PV optimizer output and repeated restarts can impact power generation efficiency at best, and even damage components at worst. This long-term damage not only reduces the lifespan of the PV optimizer but also severely impacts the normal operation of the PV system. Therefore, improving the stability and reliability of PV optimizers is an urgent issue. Summary of the Invention

[0005] In view of this, embodiments of the present application provide a photovoltaic optimizer and a control method to solve at least one problem existing in the background technology.

[0006] In a first aspect, an embodiment of the present application provides a photovoltaic optimizer control method, which is applied to a photovoltaic system, wherein the photovoltaic system includes: an inverter, a photovoltaic string, and a central controller, wherein the photovoltaic string is connected to the central controller and the inverter, respectively; the photovoltaic string includes a plurality of photovoltaic units connected in series, each of the photovoltaic units includes the photovoltaic optimizer and at least one photovoltaic module connected to the photovoltaic optimizer, the photovoltaic optimizer includes a controller and a voltage conversion circuit, the controller is configured to output a PWM signal to control the on and off of a switch tube in the voltage conversion circuit; the method includes:

[0007] Obtaining the input voltage of the photovoltaic optimizer; wherein the input voltage of the photovoltaic optimizer is the output voltage of the photovoltaic module;

[0008] Based on the input voltage, the photovoltaic optimizer is controlled to switch between a shutdown mode, a protection mode and a maximum power tracking mode; wherein,

[0009] If the input voltage is less than a first threshold, the photovoltaic optimizer operates in a shutdown mode; in the shutdown mode, the PWM signal is in a closed state;

[0010] If the input voltage is greater than or equal to a first threshold and less than or equal to a second threshold, the photovoltaic optimizer operates in a protection mode; in the protection mode, adjusting a duty cycle of a PWM signal based on the input voltage to keep the input voltage greater than the first threshold;

[0011] If the input voltage is greater than the second threshold, the photovoltaic optimizer operates in a maximum power point tracking mode; in the maximum power point tracking mode, the duty cycle of the PWM signal is adjusted based on the output voltage and output current of the photovoltaic optimizer so that the photovoltaic assembly connected to the photovoltaic optimizer operates at a maximum power point.

[0012] In a second aspect, an embodiment of the present application provides a photovoltaic optimizer, which is applied to a photovoltaic system. The photovoltaic optimizer includes:

[0013] A controller and a voltage conversion circuit, wherein the controller is used to output a PWM signal to control the on and off of a switch in the voltage conversion circuit;

[0014] Wherein, the controller includes:

[0015] An acquisition unit, configured to acquire an input voltage of the photovoltaic optimizer; wherein the input voltage of the photovoltaic optimizer is the output voltage of the photovoltaic module;

[0016] a mode selection unit, configured to control the photovoltaic optimizer to switch between an off mode, a protection mode, and a maximum power point tracking mode based on the input voltage;

[0017] in,

[0018] If the input voltage is less than a first threshold, the photovoltaic optimizer operates in a shutdown mode; in the shutdown mode, the PWM signal is in a closed state;

[0019] If the input voltage is greater than or equal to a first threshold and less than or equal to a second threshold, the photovoltaic optimizer operates in a protection mode; in the protection mode, adjusting a duty cycle of a PWM signal based on the input voltage to keep the input voltage greater than the first threshold;

[0020] If the input voltage is greater than the second threshold, the photovoltaic optimizer operates in a maximum power point tracking mode; in the maximum power point tracking mode, the duty cycle of the PWM signal is adjusted based on the output voltage and output current of the photovoltaic optimizer so that the photovoltaic assembly connected to the photovoltaic optimizer operates at a maximum power point.

[0021] In an embodiment of the present application, the photovoltaic optimizer switches between an off mode, a protection mode, and a maximum power point tracking mode by monitoring the magnitude of the input voltage. Thus, when the output power of the photovoltaic component is insufficient due to factors such as shading, maximum power point tracking may not be performed in the protection mode. Instead, the duty cycle is adjusted to keep the input voltage greater than a first threshold, thereby maintaining the normal operation of the photovoltaic optimizer and avoiding the phenomenon of repeated restarts of the photovoltaic optimizer due to power drops or insufficient power, thereby improving the stability and reliability of the photovoltaic optimizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0023] Figure 1 A schematic diagram of the structure of a photovoltaic system provided in one embodiment of the present application;

[0024] Figure 2 A schematic diagram of the voltage conversion circuit structure provided in one embodiment of the present application;

[0025] Figure 3 A schematic flow chart of a photovoltaic optimizer control method according to an embodiment of the present application;

[0026] Figure 4 A schematic diagram of a controller of a photovoltaic optimizer provided in one embodiment of the present application. DETAILED DESCRIPTION

[0027] To make the technical solutions and beneficial effects of the present invention more clearly understood, the following is a detailed description by listing specific embodiments. Unless otherwise defined, the technical and scientific terms used herein have the same meanings as those in the technical field to which this application belongs.

[0028] Figure 1 This is a schematic diagram of the structure of a photovoltaic system provided in one embodiment of the present application. Figure 1 As shown, the photovoltaic system of the embodiment of the present application includes an inverter, a photovoltaic string and a central controller, wherein the photovoltaic string is connected to the central controller and the inverter respectively; wherein the central controller is used to monitor and regulate the photovoltaic string; and the inverter is used to convert the direct current output by the photovoltaic string into alternating current and output it. The photovoltaic string includes multiple photovoltaic units connected in series. As shown in the figure, photovoltaic unit 1, photovoltaic unit 2, photovoltaic unit 3... photovoltaic unit n are connected in series and connected to the inverter. Each photovoltaic unit includes a photovoltaic optimizer and one or more photovoltaic modules connected to the photovoltaic optimizer. Specifically, photovoltaic optimizer 1, photovoltaic optimizer 2, photovoltaic optimizer 3... photovoltaic optimizer n are connected to photovoltaic modules PV1, photovoltaic modules PV2, photovoltaic modules PV3... photovoltaic modules PVn at one end, and photovoltaic optimizer 1, photovoltaic optimizer 2, photovoltaic optimizer 3... photovoltaic optimizer n at the other end are connected in series and connected to the inverter. Optionally, the central controller and the photovoltaic optimizer of each photovoltaic unit can communicate bidirectionally through the power line, thereby realizing information exchange operations such as monitoring and controlling the photovoltaic modules. The connection in the embodiments of the present application includes direct connection or indirect connection and other implementation methods, which are not specifically limited in the embodiments of the present application. For example, the central controller can communicate with the photovoltaic optimizer through magnetic ring coupling on the power line, thereby eliminating the need for additional wiring, being convenient and simple, and saving costs.

[0029] Figure 1 The photovoltaic system shown includes n photovoltaic optimizers, each of which includes a controller and a voltage conversion circuit. The controller is connected to the voltage conversion circuit, that is, photovoltaic optimizer 1, photovoltaic optimizer 2, photovoltaic optimizer 3... photovoltaic optimizer n respectively include voltage conversion circuit 1, voltage conversion circuit 2, voltage conversion circuit 3... voltage conversion circuit n and controller 1, controller 2, controller 3... controller n. Figure 1 In the photovoltaic system shown, each controller is used to output a pulse width modulation (PWM) signal to control the on and off of a switch tube in a voltage conversion circuit.

[0030] As an optional specific implementation, the voltage conversion circuit of the embodiment of the present application is a buck circuit. Correspondingly, when the buck circuit operates normally, the output voltage of the photovoltaic optimizer is less than or equal to its input voltage. Figure 2 This is a schematic diagram of the voltage conversion circuit structure provided by an embodiment of the present application. Figure 2 As shown, the voltage conversion circuit includes a main switch Q1, a bypass switch Q2, a capacitor C1, a capacitor C2, and an inductor L. The controller can control the on and off of the switch Q1 by outputting a PWM signal to adjust the output voltage and input voltage. It should be noted that the photovoltaic optimizer in the embodiment of the present application also includes a detection circuit (not shown in the figure) for detecting the voltage and current at the input and output ends of the photovoltaic optimizer. Correspondingly, the controller is connected to the detection circuit to obtain the input voltage, input current, output voltage, and output current of the photovoltaic optimizer, thereby adjusting the duty cycle of the PWM signal to track the maximum power point of the photovoltaic module. It should be noted that adjusting the duty cycle of the PWM signal will cause the output voltage to change, and will also cause the input current and input voltage to change. The PWM signal is a fixed frequency width modulation signal with a fixed switching cycle time. The duty cycle is modulated by changing the on-time within a switching cycle time. In the embodiment of the present application, the output voltage can be adjusted by changing the duty cycle of the PWM signal.

[0031] Figure 3 This is a flow chart of a photovoltaic optimizer control method provided in one embodiment of the present application. The method is applied to the photovoltaic system of the above embodiment, such as Figure 3 As shown, the method includes:

[0032] S1. Obtain the input voltage of the photovoltaic optimizer.

[0033] The input voltage of the photovoltaic optimizer is the output voltage of the photovoltaic module connected to the photovoltaic optimizer. It should be noted that in the embodiments of this application, the output voltage and output current of the photovoltaic optimizer refer to the voltage and current output to the inverter, and the output voltage and output current of the photovoltaic module refer to the voltage and current output to the photovoltaic optimizer. That is, the output voltage of the photovoltaic module is the input voltage of the photovoltaic optimizer, and the output current of the photovoltaic module is the input current of the photovoltaic optimizer.

[0034] S2. Based on the input voltage, control the PV optimizer to switch between shutdown mode, protection mode and maximum power point tracking mode.

[0035] The embodiment of the present application controls the switching of the photovoltaic optimizer mode based on the size of the input voltage. By switching the working mode, the input voltage of the photovoltaic optimizer changes smoothly, avoiding drastic changes in the input voltage due to changes in the power of the photovoltaic module, thereby improving the reliability and stability of the photovoltaic optimizer operation. It should be noted that the opening and closing of the photovoltaic optimizer is based on the size of its input voltage, while the present application switches the mode based on the input voltage of the photovoltaic optimizer without considering the size of the photovoltaic optimizer output voltage, so that the opening and closing of the photovoltaic optimizer can be controlled more accurately, thereby maintaining the stability and reliability of the photovoltaic optimizer operation. It should be noted that different working modes reflect the inconsistency of the PWM signal duty cycle. For example, in the off mode, the PWM signal is in the off state; in the maximum power tracking mode, the maximum power point of the photovoltaic module is tracked by controlling the PWM signal; in the protection mode, the maximum power point tracking is not performed by controlling the PWM signal, but the stable operation of the photovoltaic optimizer is maintained.

[0036] As an optional specific embodiment, if the input voltage is less than a first threshold, the photovoltaic optimizer is controlled to operate in a shutdown mode; in the shutdown mode, the PWM signal is in an off state. As an optional specific embodiment, the first threshold is the minimum voltage within the operating voltage range of the photovoltaic optimizer. Accordingly, when the input voltage is less than the first threshold, the photovoltaic optimizer cannot maintain normal operation, that is, the photovoltaic optimizer stops working, and enters the shutdown mode, and the corresponding PWM signal is in an off state. It should be noted that in the shutdown mode, since the photovoltaic optimizer stops working, the photovoltaic module is in an open circuit state, that is, the photovoltaic module is not connected to a load, the output current is zero, and the output voltage is an open circuit voltage.

[0037] As an optional specific implementation, if the input voltage is greater than or equal to the first threshold and less than or equal to the second threshold, the photovoltaic optimizer operates in protection mode; in protection mode, the PWM signal duty cycle is adjusted based on the input voltage to keep the input voltage greater than the first threshold. In an embodiment of the present application, in protection mode, the PWM signal duty cycle is adjusted according to the input voltage to keep the input voltage greater than the first threshold, so that the photovoltaic optimizer can be kept on when the photovoltaic module power drops suddenly or the sunlight is insufficient, preventing the photovoltaic optimizer from being shut down due to insufficient input voltage, thereby reducing the situation where the photovoltaic optimizer is repeatedly restarted. For example, since the photovoltaic module is connected by multiple photovoltaic cells in series or in parallel, when the photovoltaic module is blocked, even if the blocking area is small, it will seriously affect the output current or voltage of the photovoltaic module, thereby causing the output power to drop suddenly. At this time, the bus current in the photovoltaic system may remain relatively stable or change little due to the continued power supply of other unblocked components. At this point, if the PV optimizer for the shaded module continues to track the maximum power point, it will maintain or increase its duty cycle to output maximum power. This effectively causes the module's current supplied to the optimizer to remain constant or increase (an increased duty cycle means a longer on-time, allowing more current to flow). However, because the module's output power is reduced by the shade, maintaining or increasing the current will cause the PV optimizer's input voltage to drop sharply, which can easily cause the optimizer to shut down due to undervoltage. When the PV optimizer shuts down due to undervoltage, the PV module, without a load connected, is in an open-circuit state. The module output current then drops to zero, causing the module output voltage to exceed the optimizer's operating voltage, forcing the optimizer to restart. If the optimizer is still tracking the maximum power point, it will shut down again. This process can occur repeatedly, causing the optimizer to repeatedly restart. Consequently, these repeated restarts cause the optimizer to fluctuate between output voltage and no output voltage, resulting in severe output voltage fluctuations.

[0038] As an optional specific implementation manner, the second threshold is the lowest voltage at which the photovoltaic optimizer operates in the maximum power point tracking mode.

[0039] In the embodiments of the present application, by monitoring the input voltage, the PV optimizer operates in protection mode when the input voltage is less than or equal to a second threshold. In protection mode, maximum power point tracking is not performed. Instead, the PWM signal duty cycle is adjusted to maintain the input voltage above the first threshold. This prevents the PV optimizer from shutting down due to undervoltage, reduces repeated restarts, and maintains the stability of the PV optimizer's output voltage. It should be noted that the second threshold is greater than the first threshold. The specific value of the second threshold depends on the characteristics of the PV optimizer and the PV module and is not limited by this application.

[0040] It should be noted that output PWM signals include those with a zero duty cycle and those with a non-zero duty cycle. In shutdown mode, the PV optimizer cannot output a PWM signal, meaning the PWM signal is in the off state. However, in protection mode, the PV optimizer can operate normally, outputting a PWM signal that can be zero or non-zero depending on the input voltage. In this mode, maximum power point tracking is not performed, but the duty cycle is adjusted to maintain the PV optimizer's on state, preventing it from shutting down due to insufficient input voltage.

[0041] As an optional embodiment, in protection mode, the duty cycle of the PWM signal of the photovoltaic optimizer is adjusted based on a comparison result between the input voltage and a third threshold value, so that the input voltage approaches the third threshold value. The third threshold value is greater than the first threshold value and less than the second threshold value. Furthermore, adjusting the duty cycle of the PWM signal of the photovoltaic optimizer based on the comparison result between the input voltage and the third threshold value includes: if the input voltage is greater than the third threshold value, increasing the duty cycle of the PWM signal of the photovoltaic optimizer to reduce the input voltage at a subsequent moment, thereby bringing the input voltage closer to the third threshold value; and if the input voltage is less than the third threshold value, decreasing the duty cycle of the PWM signal of the photovoltaic optimizer to reduce the input voltage at a subsequent moment, thereby bringing the input voltage closer to the third threshold value. In the embodiment of the present application, the third threshold is a value between the first threshold and the second threshold. In protection mode, the duty cycle of the PWM signal is adjusted by comparing the input voltage with the third threshold so that the input voltage at the next moment approaches the third threshold. This, on the one hand, makes the duty cycle adjustment smoother, avoids drastic changes in the duty cycle, and thus reduces the fluctuation of the PWM signal. On the other hand, it maintains the stability of the input voltage to a certain extent, thereby keeping the output voltage of the photovoltaic optimizer relatively stable, improving the overall performance and reliability of the photovoltaic system. It should be noted that whether increasing or decreasing the duty cycle, the specific value is determined based on the difference between the input voltage and the third threshold and the current duty cycle, and this application is not limited to this. For example, the specific adjustment value can be determined by the current or input voltage feedback circuit between the photovoltaic module and the photovoltaic optimizer. It should be noted that "in protection mode" refers to being in protection mode and does not include the moment of switching from other modes to protection mode.

[0042] As an optional embodiment, if the input voltage is greater than the second threshold, the PV optimizer is controlled to operate in maximum power point tracking (MPPT) mode. In MPPT mode, a PWM signal is output based on the output voltage and output current of the PV optimizer to operate the PV modules connected to the PV optimizer at their maximum power point. Specifically, this indicates that the PV module's output power is sufficient, and adjusting the PWM signal duty cycle will not cause the input voltage to fall below the first threshold. In this case, the PV optimizer tracks the maximum power point, thereby ensuring that the PV modules output maximum power and improving the power generation efficiency of the PV system.

[0043] In the embodiment of the present application, the photovoltaic optimizer switches between the shutdown mode, the protection mode, and the maximum power point tracking mode by monitoring the magnitude of the input voltage. Therefore, when the output power of the photovoltaic module is insufficient due to factors such as shading, the maximum power point tracking can be avoided in the protection mode. Instead, the duty cycle is adjusted to keep the input voltage greater than the first threshold, thereby maintaining the normal operation of the photovoltaic optimizer, avoiding the phenomenon of repeated restarts of the photovoltaic optimizer due to power sag or power shortage, and thus improving the stability and reliability of the photovoltaic optimizer. It should be noted that the adjustment range of the duty cycle is limited. For example, the maximum adjustment range of the duty cycle is 5%-100%. In the embodiment of the present application, the duty cycle is adjusted to make the input voltage change smoothly. Therefore, when the output power of the photovoltaic module increases, decreases, or changes drastically, the input voltage of the photovoltaic optimizer can be maintained to change smoothly, thereby reducing the phenomenon of repeated restarts of the photovoltaic optimizer and improving the reliability and stability of the photovoltaic optimizer.

[0044] As an optional specific implementation, S2 includes:

[0045] If the input voltage at the previous moment is greater than the second threshold, and the input voltage at the current moment is less than or equal to the second threshold, then the duty cycle of the PWM signal of the photovoltaic optimizer is reduced at the current moment, and the photovoltaic optimizer is controlled to switch from the maximum power tracking mode to the protection mode. In the embodiment of the present application, the previous moment and the current moment are two consecutive input voltage sampling moments. The input voltage at the previous moment is greater than the second threshold, indicating that the previous moment was in the maximum power tracking mode; the input voltage at the current moment is less than or equal to the second threshold, indicating that the input voltage has decreased at the current moment. At this time, by reducing the duty cycle of the PWM signal, the input voltage can be prevented from continuing to decrease. That is, when the output power of the photovoltaic module is reduced, the output current of the photovoltaic module is reduced by reducing the duty cycle of the PWM signal, thereby preventing the output voltage of the photovoltaic module from further decreasing, and preventing the output voltage of the photovoltaic module from being less than the starting voltage of the photovoltaic optimizer, thereby maintaining the normal operation of the photovoltaic optimizer and avoiding the shutdown of the photovoltaic optimizer. Correspondingly, the photovoltaic optimizer is controlled to switch from the maximum power tracking mode to the protection mode to keep the output voltage of the photovoltaic module greater than the first threshold. For example, at the previous moment T of a photovoltaic module, n At this moment, the input voltage is greater than the second threshold, and the maximum power tracking mode is in effect. Due to shading or sunset, the reduced light intensity will cause the output power of the photovoltaic module to decrease, resulting in the current moment T n+1 When the input voltage is less than or equal to the second threshold, the decreasing speed of the output voltage of the photovoltaic module can be slowed down by reducing the duty cycle, that is, V n+2 -V n+1 <V n+1 -V n , where V n Indicates T n The output voltage of the photovoltaic module at this moment, V n+1 Indicates T n+1 The output voltage of the photovoltaic module at this moment, V n+2 Indicates T n+2 The output voltage of the photovoltaic module at the moment, T n+2 Time is T n+1The next moment after the moment. It should be noted that when a photovoltaic module is blocked, since the bus current does not change much, the degree of drop in the photovoltaic module output voltage can be reduced by reducing the duty cycle. If the output power of all photovoltaic modules is generally reduced at sunset, the bus current will also decrease. At this time, the photovoltaic optimizer can reduce the duty cycle to slow down the drop in the photovoltaic module output voltage, maintain the output of the photovoltaic optimizer, and maintain the smooth operation of the photovoltaic system, thereby realizing a slow shutdown of the photovoltaic system, avoiding system fluctuations caused by power mutations, and ensuring a smooth transition of the photovoltaic system at sunset. In the embodiment of the present application, when the power of the photovoltaic module decreases due to factors such as blocking or sunset, by monitoring the input voltage, the maximum power tracking mode is switched to the protection mode when the input voltage is less than the second threshold, and the duty cycle of the PWM signal is reduced, thereby effectively slowing down the input voltage drop, effectively avoiding the phenomenon of a sudden drop in the photovoltaic optimizer input voltage (i.e., the output voltage of the photovoltaic module) due to the reduction in photovoltaic module output power, and maintaining the effective output of the photovoltaic optimizer.

[0046] Furthermore, reducing the duty cycle of the PWM signal of the photovoltaic optimizer at the current moment includes:

[0047] If the current input voltage is less than the third threshold, the duty cycle of the PWM signal of the photovoltaic optimizer is reduced at the current moment based on the input voltage at the previous moment and the current input voltage; if the current input voltage is greater than the third threshold, the duty cycle of the PWM signal of the photovoltaic optimizer is reduced at the current moment based on the input voltage at the previous moment and the third threshold. In an embodiment of the present application, the duty cycle is adjusted at the current moment based on the comparison between the input voltage and the third threshold, thereby further reducing the fluctuation of the input voltage. Specifically: if the current input voltage is less than the third threshold, the duty cycle of the PWM signal is reduced based on the difference between the input voltage at the previous moment and the input voltage at the current moment. At this time, the difference is larger, and the PWM signal reduction amplitude is also larger, thereby minimizing the decrease in the input voltage; if the current input voltage is greater than the third threshold, the duty cycle of the PWM signal is reduced based on the difference between the input voltage at the previous moment and the third threshold. This not only slows down the decrease in the input voltage, but also makes the input voltage as close to the third threshold as possible, thereby maintaining the stability of the input voltage through adjustment, and also making the output voltage change smoothly, avoiding severe jitter of the output voltage. For example, if the first threshold is 12V, the second threshold is 14V, and the third threshold is 13V, and the current input voltage is between 12V and 13V, the difference between the previous input voltage and the current input voltage is greater, and the duty cycle is reduced more significantly, thereby minimizing the decrease in input voltage. If the current input voltage is between 13V and 14V, the duty cycle is adjusted based on the difference between the third threshold and the current input voltage, thereby adjusting the input voltage toward the third threshold and maintaining input voltage stability. It should be noted that the greater the difference, the greater the duty cycle adjustment. If the output power of the photovoltaic module remains unchanged, increasing the duty cycle will increase the on-time, allowing more current, that is, the photovoltaic module output current will increase, and correspondingly, the photovoltaic module output voltage will decrease. Reducing the duty cycle will reduce the output current, and correspondingly, the photovoltaic module output voltage will increase.

[0048] As an optional specific implementation, S2 further includes:

[0049] If the input voltage at the previous moment is less than the first threshold, and the input voltage at the current moment is greater than the first threshold and less than the third threshold, the photovoltaic optimizer is controlled to switch from the shutdown mode to the protection mode at the current moment; a PWM signal with a duty cycle of zero is output at the current moment until the input voltage at a certain moment is greater than the third threshold, at which time the duty cycle of the PWM signal is increased. Specifically, the duty cycle of the PWM signal is determined based on the input voltage at a certain moment and the third threshold. If the input voltage at the previous moment is less than the first threshold, and the input voltage at the current moment is greater than the third threshold, the photovoltaic optimizer is controlled to switch from the shutdown mode to the protection mode, and the duty cycle of the PWM signal is increased at the current moment. Specifically, the duty cycle of the PWM signal is determined based on the input voltage at the current moment and the third threshold. In an embodiment of the present application, when the power of the photovoltaic module increases, the duty cycle of the PWM signal is flexibly adjusted by monitoring the difference between the input voltage and the third threshold to stabilize the input voltage, prevent repeated restarts caused by sudden drops, and ensure the stability of the output voltage of the photovoltaic optimizer. Specifically, when the input voltage is less than a third threshold, a PWM signal with a zero duty cycle is output. At this time, the input voltage is still relatively low, and the photovoltaic module can form a path with the photovoltaic optimizer but does not output voltage to the inverter. This prevents the duty cycle from suddenly turning on, causing the input voltage to drop sharply, when the input voltage is low, effectively avoiding repeated restarts of the photovoltaic optimizer. When the input voltage is greater than or equal to the third threshold, the photovoltaic module has reached a certain power level, and the corresponding photovoltaic optimizer input voltage is also relatively large. At this time, the duty cycle is determined based on the difference between the input voltage and the third threshold, i.e., a PWM signal with a non-zero duty cycle is output. This allows the input voltage to remain near the third threshold for a period of time, thereby making the output voltage of the photovoltaic optimizer more stable. In this embodiment of the present application, during the process of increasing the power of the photovoltaic module, by comparing the input voltage with the third threshold, the PWM duty cycle is flexibly modulated, effectively resolving the output voltage fluctuation problem that may occur during the photovoltaic module power increase process and ensuring the stable startup and operation of the photovoltaic optimizer. It should be noted that voltage or current sensors can be configured in the photovoltaic system to monitor the output voltage and current of the photovoltaic modules in real time. The sensors can work independently of the photovoltaic optimizer. The corresponding photovoltaic optimizer can trigger the corresponding control logic when the input voltage changes according to the preset control logic.

[0050] The present application also provides a photovoltaic optimizer, which is applied to the photovoltaic system of the above embodiment. The photovoltaic optimizer includes:

[0051] A controller and a voltage conversion circuit, wherein the controller is used to output a PWM signal to control the on and off of a switch tube in the voltage conversion circuit.

[0052] Figure 4 FIG2 is a schematic diagram of a controller of a photovoltaic optimizer according to an embodiment of the present application. As shown in the figure, the controller includes:

[0053] An acquisition unit 301 is configured to acquire an input voltage of a photovoltaic optimizer, wherein the input voltage of the photovoltaic optimizer is the output voltage of the photovoltaic module;

[0054] The mode selection unit 302 is configured to control the photovoltaic optimizer to switch between a shutdown mode, a protection mode, and a maximum power point tracking mode based on the input voltage.

[0055] Among them, if the input voltage is less than the first threshold, the photovoltaic optimizer operates in the shutdown mode; in the shutdown mode, the PWM signal is in the off state; if the input voltage is greater than or equal to the first threshold and less than or equal to the second threshold, the photovoltaic optimizer operates in the protection mode; in the protection mode, the duty cycle of the PWM signal is adjusted based on the input voltage to keep the input voltage greater than the first threshold; if the input voltage is greater than the second threshold, the photovoltaic optimizer operates in the maximum power tracking mode; in the maximum power tracking mode, the duty cycle of the PWM signal is adjusted based on the output voltage and output current of the photovoltaic optimizer so that the photovoltaic components connected to the photovoltaic optimizer operate at the maximum power point.

[0056] Optionally, in the protection mode, the duty cycle of the PWM signal of the photovoltaic optimizer is adjusted according to the comparison result between the input voltage and a third threshold; wherein the third threshold is greater than the first threshold and less than the second threshold.

[0057] Optionally, in the protection mode, adjusting the duty cycle of the PWM signal of the photovoltaic optimizer according to the comparison result between the input voltage and the third threshold value includes:

[0058] If the input voltage is greater than a third threshold, increasing the duty cycle of the photovoltaic optimizer PWM signal;

[0059] If the input voltage is less than the third threshold, the duty cycle of the photovoltaic optimizer PWM signal is reduced.

[0060] Optionally, based on the input voltage, controls the PV optimizer to switch between shutdown mode, protection mode, and maximum power point tracking mode, including:

[0061] If the input voltage at the previous moment is greater than the second threshold and the input voltage at the current moment is less than or equal to the second threshold, the duty cycle of the PWM signal of the photovoltaic optimizer is reduced at the current moment, and the photovoltaic optimizer is controlled to switch from the maximum power point tracking mode to the protection mode.

[0062] Optionally, reducing the duty cycle of the PWM signal of the photovoltaic optimizer at the current moment includes:

[0063] If the input voltage at the current moment is less than the third threshold, then at the current moment, the duty cycle of the PWM signal of the photovoltaic optimizer is reduced according to the input voltage at the previous moment and the input voltage at the current moment;

[0064] If the input voltage at the current moment is greater than the third threshold, the duty cycle of the PWM signal of the photovoltaic optimizer is reduced at the current moment according to the input voltage at the previous moment and the third threshold.

[0065] Optionally, based on the input voltage, controls the PV optimizer to switch between shutdown mode, protection mode, and maximum power point tracking mode, including:

[0066] If the input voltage at the previous moment is less than the first threshold, and the input voltage at the current moment is greater than the first threshold and less than the third threshold, the photovoltaic optimizer is controlled to switch from the shutdown mode to the protection mode at the current moment; a PWM signal with a duty cycle of zero is output at the current moment, and the duty cycle of the PWM signal is increased when the input voltage at a certain moment is greater than the third threshold;

[0067] If the input voltage at the previous moment is less than the first threshold and the input voltage at the current moment is greater than the third threshold, the photovoltaic optimizer is controlled to switch from the shutdown mode to the protection mode and the duty cycle of the PWM signal is increased; wherein the third threshold is greater than the first threshold and less than the second threshold.

[0068] Optionally, the first threshold is the minimum voltage within the operating voltage range of the photovoltaic optimizer; and the second threshold is the lowest voltage when the photovoltaic optimizer operates in the maximum power point tracking mode.

[0069] It should be noted that the photovoltaic optimizer control method embodiment and the photovoltaic optimizer embodiment provided in the embodiments of the present application belong to the same concept; the technical features in the technical solutions recorded in each embodiment can be arbitrarily combined without conflict.

[0070] It should be understood that the above embodiments are exemplary and are not intended to encompass all possible implementations of the claims. Various modifications and variations may be made to the above embodiments without departing from the scope of this disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form additional embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments merely illustrate several implementations of the present invention and do not limit the scope of protection of the patent of this invention.

Claims

1. A photovoltaic optimizer control method, characterized in that: The method is applied to a photovoltaic system, which includes an inverter, a photovoltaic string, and a central controller, wherein the photovoltaic string is connected to the central controller and the inverter, respectively; the photovoltaic string includes a plurality of photovoltaic units connected in series, each of the photovoltaic units includes the photovoltaic optimizer and at least one photovoltaic module connected to the photovoltaic optimizer, the photovoltaic optimizer includes a controller and a voltage conversion circuit, the controller is configured to output a PWM signal to control the on / off of a switch in the voltage conversion circuit; the method includes: Obtaining the input voltage of the photovoltaic optimizer; wherein the input voltage of the photovoltaic optimizer is the output voltage of the photovoltaic module; Based on the input voltage, the photovoltaic optimizer is controlled to switch between a shutdown mode, a protection mode and a maximum power tracking mode; wherein, If the input voltage is less than a first threshold, the photovoltaic optimizer operates in a shutdown mode; in the shutdown mode, the PWM signal is in a closed state; If the input voltage is greater than or equal to a first threshold and less than or equal to a second threshold, the photovoltaic optimizer operates in a protection mode; in the protection mode, the duty cycle of the PWM signal is adjusted based on the input voltage to keep the input voltage greater than the first threshold; wherein, in the protection mode, the duty cycle of the PWM signal of the photovoltaic optimizer is adjusted based on a comparison result of the input voltage with a third threshold so that the input voltage approaches the third threshold; wherein the third threshold is greater than the first threshold and less than the second threshold; If the input voltage is greater than the second threshold, the photovoltaic optimizer operates in a maximum power point tracking mode; in the maximum power point tracking mode, the duty cycle of the PWM signal is adjusted based on the output voltage and output current of the photovoltaic optimizer so that the photovoltaic assembly connected to the photovoltaic optimizer operates at a maximum power point.

2. The photovoltaic optimizer control method according to claim 1, wherein: In the protection mode, adjusting the duty cycle of the PWM signal of the photovoltaic optimizer according to the comparison result of the input voltage and the third threshold value includes: If the input voltage is greater than a third threshold, increasing the duty cycle of the photovoltaic optimizer PWM signal; If the input voltage is less than the third threshold, the duty cycle of the photovoltaic optimizer PWM signal is reduced.

3. The photovoltaic optimizer control method according to claim 1, wherein: Based on the input voltage, controlling the photovoltaic optimizer to switch between a shutdown mode, a protection mode, and a maximum power point tracking mode includes: If the input voltage at the previous moment is greater than the second threshold and the input voltage at the current moment is less than or equal to the second threshold, the duty cycle of the PWM signal of the photovoltaic optimizer is reduced at the current moment, and the photovoltaic optimizer is controlled to switch from the maximum power point tracking mode to the protection mode.

4. The photovoltaic optimizer control method according to claim 3, wherein: Reducing the duty cycle of the PWM signal of the photovoltaic optimizer at the current moment includes: If the input voltage at the current moment is less than a third threshold, reducing the duty cycle of the PWM signal of the photovoltaic optimizer at the current moment according to the input voltage at the previous moment and the input voltage at the current moment; If the input voltage at the current moment is greater than the third threshold, the duty cycle of the PWM signal of the photovoltaic optimizer is reduced at the current moment according to the input voltage at the previous moment and the third threshold.

5. The photovoltaic optimizer control method according to claim 1, wherein: Based on the input voltage, controlling the photovoltaic optimizer to switch between a shutdown mode, a protection mode, and a maximum power point tracking mode includes: If the input voltage at the previous moment is less than the first threshold, and the input voltage at the current moment is greater than the first threshold and less than the third threshold, then at the current moment, the photovoltaic optimizer is controlled to switch from the shutdown mode to the protection mode; a PWM signal with a duty cycle of zero is output at the current moment, and the duty cycle of the PWM signal is increased until the input voltage at a certain moment is greater than the third threshold; If the input voltage at the previous moment is less than the first threshold and the input voltage at the current moment is greater than a third threshold, the photovoltaic optimizer is controlled to switch from the shutdown mode to the protection mode, and the duty cycle of the PWM signal is increased; wherein the third threshold is greater than the first threshold and less than the second threshold.

6. A photovoltaic optimizer, applied to a photovoltaic system, characterized in that: The photovoltaic system includes: an inverter, a photovoltaic string, and a central controller, wherein the photovoltaic string is connected to the central controller and the inverter respectively; the photovoltaic string includes a plurality of photovoltaic units connected in series, each of the photovoltaic units includes the photovoltaic optimizer and at least one photovoltaic assembly connected to the photovoltaic optimizer, and the photovoltaic optimizer includes: A controller and a voltage conversion circuit, wherein the controller is used to output a PWM signal to control the on and off of a switch in the voltage conversion circuit; Wherein, the controller includes: An acquisition unit, configured to acquire an input voltage of the photovoltaic optimizer; wherein the input voltage of the photovoltaic optimizer is the output voltage of the photovoltaic module; a mode selection unit, configured to control the photovoltaic optimizer to switch between an off mode, a protection mode, and a maximum power point tracking mode based on the input voltage; in, If the input voltage is less than a first threshold, the photovoltaic optimizer operates in a shutdown mode; in the shutdown mode, the PWM signal is in a closed state; If the input voltage is greater than or equal to a first threshold and less than or equal to a second threshold, the photovoltaic optimizer operates in a protection mode; in the protection mode, the duty cycle of the PWM signal is adjusted based on the input voltage to keep the input voltage greater than the first threshold; wherein, in the protection mode, the duty cycle of the PWM signal of the photovoltaic optimizer is adjusted based on a comparison result of the input voltage with a third threshold so that the input voltage approaches the third threshold; wherein the third threshold is greater than the first threshold and less than the second threshold; If the input voltage is greater than the second threshold, the photovoltaic optimizer operates in a maximum power point tracking mode; in the maximum power point tracking mode, the duty cycle of the PWM signal is adjusted based on the output voltage and output current of the photovoltaic optimizer so that the photovoltaic assembly connected to the photovoltaic optimizer operates at a maximum power point.

7. The photovoltaic optimizer according to claim 6, wherein: In the protection mode, adjusting the duty cycle of the PWM signal of the photovoltaic optimizer according to the comparison result of the input voltage and the third threshold value includes: If the input voltage is greater than a third threshold, increasing the duty cycle of the photovoltaic optimizer PWM signal; If the input voltage is less than the third threshold, the duty cycle of the photovoltaic optimizer PWM signal is reduced.

Images