Photovoltaic inverter and power control method

Abstract

The invention provides a photovoltaic inverter and a power control method, the photovoltaic inverter comprises an inverter circuit, a plurality of transformation circuits, a plurality of acquisition circuits and a control circuit, and one transformation circuit comprises at least one switch tube. And the plurality of acquisition circuits are used for detecting the input voltage of the target transformation circuit and the voltage of the BUS. The control circuit is used for adjusting the current threshold value of the target transformation circuit according to the input voltage of the target transformation circuit and the voltage of the BUS; and when the input current of the target voltage transformation circuit is greater than or equal to the current threshold value of the target voltage transformation circuit, adjusting on or off of a switching tube in the target voltage transformation circuit so as to reduce the current or input power of the target voltage transformation circuit. According to the invention, when the input current of the target transformation circuit is greater than or equal to the current threshold value of the target transformation circuit, the input power of the transformation circuit is reduced, the power supply safety is ensured, the stability and the power supply efficiency of the photovoltaic inverter are improved, the structure is simple, the method is simple and convenient, and the applicability is high.

Description

[0001] This application is a divisional application. The application number of the original application is 202310007315.8, and the original application date is January 4, 2023. The entire contents of the original application are incorporated into this application by reference. Technical Field

[0002] The present application relates to the field of power electronics technology, and in particular to a photovoltaic inverter and a power control method. Background Art

[0003] In the field of power electronics, the inverter circuit in the photovoltaic inverter is usually used to convert DC power into AC power so that the power can be transmitted between the power source and the load. For example, in the field of photovoltaic power supply, the photovoltaic inverter can convert the DC power output by the DC power source (for example, photovoltaic Photovoltaic, PV panel) into AC power and provide it to the load or the power grid. Usually, the control circuit in the photovoltaic inverter (for example, the Maximum Power Point Tracking, MPPT control circuit) will control the output current of the PV panel (that is, the input current of the photovoltaic inverter) according to the output voltage of the PV panel (that is, the input voltage of the photovoltaic inverter), so that the PV panel outputs power to the load at maximum power. The inventors of this application found in the process of research and practice that in the prior art, the photovoltaic inverter usually converts the DC voltage provided by each group of PV panels into a DC bus voltage (for example, the voltage of each group of PV panels is stepped up and converted into a BUS bus voltage) through multiple transformer circuits, and then converts the DC power into AC power through the inverter circuit to adapt to the voltage of various loads. Due to the differences between groups of PV panels (for example, different lengths, different light intensities, etc.), when the difference between the output voltage of the PV panels connected to a certain transformer circuit (that is, the input voltage of the transformer circuit) and the BUS voltage is too large, the input current in the transformer circuit is usually also relatively large. As a result, the components in the transformer circuit (for example, the switching tube in the transformer circuit) may fail or be damaged due to overvoltage, overcurrent or overheating. Summary of the invention

[0004] The present application provides a photovoltaic inverter and a power control method, which can adjust the duty cycle of the switch tube through a control circuit to reduce the input power of the transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, thereby improving the stability and power supply efficiency of the photovoltaic inverter while ensuring power supply safety. The application has a simple structure, a simple method and strong applicability.

[0005] In the first aspect, the present application provides a photovoltaic inverter, which may include an inverter circuit, multiple transformer circuits, multiple acquisition circuits and a control circuit, and a transformer circuit may include at least one switch tube. Here, one end of each transformer circuit can be used to respectively connect to each group of photovoltaic panels in a plurality of photovoltaic panels, and the other end of each transformer circuit can be used to connect to the load through the inverter circuit after being connected in parallel to the BUS bus. Multiple acquisition circuits can be connected to the control circuit and used to detect the voltage or current of multiple transformer circuits and the BUS bus, and the control circuit connects the switch tubes in each transformer circuit. The multiple acquisition circuits here can be used to detect the input voltage of the target transformer circuit and the voltage of the BUS bus, wherein the target transformer circuit is any one or any several transformer circuits among the multiple transformer circuits. The control circuit here can adjust the current threshold of the target transformer circuit based on the input voltage of the target transformer circuit and the voltage of the BUS bus. The control circuit here can also be used to adjust the duty cycle of the switch tube in the target transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, so as to adjust the conduction or shutdown of the switch tube in the target transformer circuit to reduce the current or input power of the target transformer circuit.

[0006] In the present application, the photovoltaic panel can be used as a DC power source to connect the load through a photovoltaic inverter, and the photovoltaic inverter can convert the DC power provided by the photovoltaic panel into AC power and provide it to the load. Here, the photovoltaic inverter may include an inverter circuit and multiple transformer circuits, and the DC power source may be composed of multiple groups of photovoltaic panels (each group of photovoltaic panels may include one photovoltaic panel or multiple photovoltaic panels), and each group of photovoltaic panels may be connected to the inverter circuit through a transformer circuit. The transformer circuit can convert the DC voltage provided by the photovoltaic panel into a BUS bus voltage, and then convert the DC power into AC power through the inverter circuit, so that the AC voltage output by the photovoltaic inverter can adapt to loads of various voltage ranges. In an application scenario involving multiple groups of photovoltaic panels, due to the differences between the photovoltaic panels of each group (for example, different lengths, different shapes, different light intensities, etc.), when the difference between the output voltage of the photovoltaic panel connected to a certain transformer circuit (that is, the input voltage of the transformer circuit) and the BUS bus voltage is too large, the input current in the transformer circuit is usually also relatively large, and then, the components in the transformer circuit (for example, the switch tube in the transformer circuit) may fail or be damaged due to overvoltage (voltage difference is too large), overcurrent (current is too large) or overheating (temperature is too high). Here, the photovoltaic inverter may also include a control circuit and a collection circuit, and the collection circuit can detect the power supply parameters of the photovoltaic inverter (for example, the input voltage and / or output voltage of the transformer circuit, the input current and / or output current of the transformer circuit, the temperature of the transformer circuit, the BUS bus voltage and / or current, the input voltage and / or output voltage of the inverter circuit, the input current and / or output current of the inverter circuit, the temperature of the inverter circuit, etc.). Here, the control circuit can judge the working state of the photovoltaic inverter based on the power supply parameters of the photovoltaic inverter. Here, taking the one (or more) transformer circuits that the control circuit needs to control as the target transformer circuit as an example, the control circuit can adjust the current threshold of the target transformer circuit based on the input voltage of the target transformer circuit and the voltage of the BUS bus. After obtaining the current threshold of the target transformer circuit, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, in order to protect the working safety of the transformer circuit, the control circuit can adjust the duty cycle of the switch tube in the target transformer circuit (for example, reduce the duty cycle of the switch tube in the target transformer circuit) to adjust the conduction or shutdown of the switch tube in the target transformer circuit, thereby reducing the current or input power of the target transformer circuit.

[0007] By adopting the present application, the photovoltaic inverter can adjust the duty cycle of the switch tube through the control circuit to reduce the input power of the transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, thereby improving the stability and power supply efficiency of the photovoltaic inverter while ensuring power supply safety. The structure is simple, the method is simple, and the applicability is strong.

[0008] In combination with the first aspect, in a first possible implementation, the acquisition circuit may also be used to detect the temperature of the target transformer circuit. The control circuit may also be used to adjust the current threshold of the target transformer circuit to a first current threshold based on the input voltage of the target transformer circuit and the voltage of the BUS bus when the temperature of the target transformer circuit is greater than or equal to the temperature threshold. It can be understood that the control circuit can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to control the input power (or input current) of the target transformer circuit. In other words, the control circuit can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to adjust the duty cycle of the switch tube in the target transformer circuit. For example, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, it can be considered that the target transformer circuit is in a working state where the input power needs to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively harsh, and the risk of damage is relatively high if it continues to work), at this time, the control circuit needs to reduce the input current and / or input power of the target transformer circuit. Here, when the operating temperature of the switch tube in the target transformer circuit is different, even if the voltage difference borne by the switch tube is the same, the input current that the switch tube can withstand may be different. For example, when the operating temperature of the switch tube in the target transformer circuit is high (for example, the temperature of the target transformer circuit is greater than or equal to the temperature threshold), the control circuit can determine the maximum input current (for example, the first current threshold) that the switch tube in the target transformer circuit can withstand based on the voltage difference borne by the switch tube in the target transformer circuit (for example, the difference between the input voltage of the target transformer circuit and the voltage of the BUS bus). It should be noted that the value of the first current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when bearing different voltage differences), and can also be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage. For example, a photovoltaic inverter or an external central control system can calculate the relationship curve of the current threshold corresponding to the switch tube when it bears different voltage differences at a certain operating temperature or a certain operating temperature range (for example, a first operating temperature range greater than or equal to the temperature threshold) during the operation (or design process) of the transformer circuit, and then the control circuit can obtain the first current threshold based on this relationship curve, which can be set according to the application scenario. It can be understood that the first current threshold here can be a current, multiple discrete currents, or a current range composed of multiple discrete currents or continuous currents.

[0009] In the present application, when the operating temperature of the switch tube in the target transformer circuit is high (for example, the temperature of the target transformer circuit is greater than or equal to the temperature threshold), if the input current of the switch tube in the target transformer circuit is greater than or equal to the first current threshold, it means that the target transformer circuit is in a working state that needs to be adjusted. The control circuit can reduce the duty cycle of the switch tube in the target transformer circuit, thereby reducing the input power of the target transformer circuit to avoid damage to the components in the target transformer circuit due to overheating, thereby improving the safety of the target transformer circuit. At the same time, because the control circuit does not completely shut down the input power of the target transformer circuit, the transmission efficiency of the power is ensured on the basis of ensuring safety.

[0010] Combined with the first possible implementation manner of the first aspect, in the second possible implementation manner, the control circuit can also be used to adjust the current threshold of the target voltage conversion circuit to a second current threshold based on the input voltage of the target voltage conversion circuit and the voltage of the BUS bus when the temperature of the target voltage conversion circuit is less than the temperature threshold, where the second current threshold is greater than or equal to the first current threshold. It can be understood that the control circuit can determine the working state of the target voltage conversion circuit in various ways, and then determine whether it is necessary to control the input power (or input current) of the target voltage conversion circuit. In other words, the control circuit can determine the working state of the target voltage conversion circuit in various ways, and then determine whether it is necessary to adjust the duty cycle of the switching tube in the target voltage conversion circuit. For example, when the input current of the target voltage conversion circuit is greater than or equal to the current threshold of the target voltage conversion circuit, it can be considered that the target voltage conversion circuit is in a working state that requires reducing the input power (or in other words, the working environment of the switching tube in the target voltage conversion circuit is relatively harsh, and the risk of damage is relatively high if it continues to work). At this time, the control circuit needs to reduce the input current and / or input power of the target voltage conversion circuit. Here, when the working temperature of the switching tube in the target voltage conversion circuit is different, even if the voltage difference borne by the switching tube is the same, the input current that the switching tube can withstand may also be different. For example, when the working temperature of the switching tube in the target voltage conversion circuit is relatively low (for example, the temperature of the target voltage conversion circuit is less than the temperature threshold), the control circuit can determine the maximum input current (for example, the second current threshold) that the switching tube in the target voltage conversion circuit can withstand based on the voltage difference borne by the switching tube in the target voltage conversion circuit (for example, the difference between the input voltage of the target voltage conversion circuit and the voltage of the BUS bus). Here, the second current threshold is less than or equal to the first voltage threshold. It should be noted that the value of the second current threshold can be determined based on the maximum input current of the switching tube in the target voltage conversion circuit (for example, determined based on the nominal current corresponding to various types of switching tubes when bearing different voltage differences), or can be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection, storage, or other means. For example, the photovoltaic inverter or an external central control system can calculate the relationship curve of the current threshold corresponding to the switching tube when bearing different voltage differences during the working process (or design process) of the voltage conversion circuit, for example, in a certain working temperature or a certain working temperature range (for example, in the second working temperature range less than the temperature threshold), and then the control circuit can obtain the second current threshold based on this relationship curve, which can be specifically set according to the application scenario. It can be understood that the second current threshold here can be a current, can be multiple discrete currents, or can be a current interval composed of multiple discrete currents or continuous currents.

[0011] In the present application, when the operating temperature of the switch tube in the target transformer circuit is low (for example, the temperature of the target transformer circuit is less than the temperature threshold), if the input current of the switch tube in the target transformer circuit is greater than or equal to the second current threshold, it means that the target transformer circuit is in a working state that needs to be adjusted. The control circuit can reduce the duty cycle of the switch tube in the target transformer circuit, thereby reducing the input power of the target transformer circuit to avoid damage to the components in the target transformer circuit due to overheating, thereby improving the safety of the target transformer circuit. At the same time, because the control circuit does not completely shut down the input power of the target transformer circuit, the transmission efficiency of the power is ensured on the basis of ensuring safety.

[0012] In combination with the first aspect or any possible implementation of the first aspect, in a third possible implementation, the control circuit may also be used to generate a switch modulation signal based on the input current of the target transformer circuit and the current threshold of the target transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, and control the duty cycle of the switch tube in the target voltage circuit through the switch modulation signal to adjust the on or off of the switch tube in the target transformer circuit. Here, the control circuit (for example, a current regulation loop (for example, a proportional regulation circuit or a proportional integral regulation circuit) and a drive control circuit, or other circuits with a current regulation function and a drive control function) can generate a switch modulation signal based on the input current of the target transformer circuit and the current threshold of the target transformer circuit to control the duty cycle of the switch tube in the target transformer circuit. For example, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, the control circuit can generate a reference value less than the current threshold based on the current threshold of the target transformer circuit, and use the input current of the target transformer circuit as a variable to be adjusted, and generate a switch modulation signal to control the duty cycle of the switch tube in the target transformer circuit through the switch modulation signal, thereby adjusting the input current in the target transformer circuit to less than the current threshold of the target transformer circuit (that is, the aforementioned reference value). Here, the control circuit can generate a pulse width modulation signal such as Pulse Width Modulation, PWM wave as a switch modulation signal, or generate a drive pulse signal based on the PWM wave as a switch modulation signal. Here, the switch modulation signal can control the duty cycle of the switch tube in the target transformer circuit, thereby controlling the input current and / or input power of the target transformer circuit. For example, the control circuit can reduce the duty cycle of the switch tube in the target transformer circuit to reduce the input current of the target transformer circuit, thereby reducing the input power of the target transformer circuit. It can be understood that the control circuit provided in the present application can use discontinuous pulse width modulation (DPWM) wave as the switching modulation signal, and can also use other PWM waves (for example, sinusoidal pulse width modulation (SPWM) wave, third harmonic injection pulse width modulation (THIPWM) wave, carrier based space vector pulse width modulation (CBPWM) wave, etc.) as the switching modulation signal, and can also use the driving pulse signal generated based on these PWM waves as the switching modulation signal. It has a wide range of application scenarios and good control effect.

[0013] In combination with the first aspect or any possible implementation manner of the first aspect, in a fourth possible implementation manner, the control circuit can also be used to adjust the duty cycle of the switching tube in the target transformer circuit when the input current of the target transformer circuit is less than the current threshold of the target transformer circuit, so as to adjust the conduction or shutdown of the switching tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power.

[0014] Here, when the input current of the target transformer circuit is less than the current threshold of the target transformer circuit (for example, the third current threshold), it can be considered that the target transformer circuit is in a working state where the input power does not need to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively safe and the risk of damage is relatively small). At this time, the control circuit can adjust the duty cycle of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power (for example, so that the photovoltaic panel connected to the target transformer circuit operates at the maximum power point). Here, the value of the third current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when they bear different voltage differences), or it can be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage. For example, the photovoltaic inverter or the external central control system can calculate the relationship curve of the current threshold corresponding to the switch tube when it bears different voltage differences during the operation (or design) of the transformer circuit at a certain operating temperature or a certain operating temperature interval (for example, in a first operating temperature interval greater than or equal to the temperature threshold, or in a second operating temperature interval less than the temperature threshold), and then the control circuit can obtain the third current threshold based on this relationship curve, which can be set according to the application scenario. It can be understood that the third current threshold here can be a current, a plurality of discrete currents, or a current interval composed of a plurality of discrete currents or continuous currents. For example, in a first operating temperature interval greater than or equal to the temperature threshold, the third current threshold can be less than or equal to the first current threshold. For another example, in a second operating temperature interval less than the temperature threshold, the third current threshold can be less than or equal to the second current threshold. When the third voltage threshold is less than the first current threshold (or the second current threshold), the photovoltaic inverter can avoid repeatedly reducing or increasing the input power of the target transformer circuit through the control circuit when the input current of the target transformer circuit is not stably less than the first current threshold (or the second current threshold). That is to say, when the third voltage threshold is less than the first current threshold (or the second current threshold), the photovoltaic inverter can put the target transformer circuit in an operating state where the input power does not need to be reduced (or the working environment of the switch tube in the target transformer circuit is safer and the risk of damage is lower) after the input current of the target transformer circuit is stable (for example, stably less than the third current threshold), and the target transformer circuit is in an operating state where the input power does not need to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is safer and the risk of damage is lower. At this time, the control circuit can adjust the duty cycle of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power (for example, so that the photovoltaic panel connected to the target transformer circuit operates at the maximum power point), thereby improving the power supply efficiency.

[0015] In combination with the first aspect or any possible implementation of the first aspect, in a fifth possible implementation, the inverter circuit may include a switch tube, and the control circuit may also be used to adjust the duty cycle of the switch tube in the inverter circuit when the voltage of the BUS bus is greater than or equal to the bus voltage threshold, so as to adjust the on or off of the switch tube in the inverter circuit to reduce the output power of the inverter circuit. It can be understood that the control circuit can determine the working state of the photovoltaic inverter in a variety of ways, and then determine whether it is necessary to control the output power (or output current) of the photovoltaic inverter (for example, the inverter circuit). For example, when the voltage of the BUS bus is greater than or equal to the bus voltage threshold, it can be considered that the inverter circuit is in a working state where the output power needs to be reduced (or in other words, the working environment of each component in the photovoltaic inverter is relatively bad, and the risk of damage is relatively high if it continues to work), at this time, the control circuit needs to reduce the output current and / or output power of the inverter circuit. It can be understood that the bus voltage threshold here can be a voltage, can be a plurality of discrete voltages, can be a voltage interval composed of a plurality of discrete voltages or a continuous voltage.

[0016] In the present application, when the voltage of the BUS is high (for example, the voltage of the BUS is greater than or equal to the bus voltage threshold), it indicates that the photovoltaic inverter is in a working state where the output power needs to be reduced. The control circuit can reduce the duty cycle of each switch tube in the inverter circuit, thereby reducing the output power of the inverter circuit to avoid damage to components in the photovoltaic inverter due to overheating, thereby further improving power supply safety.

[0017] In the second aspect, the present application provides a power control method, which is suitable for a photovoltaic inverter. The photovoltaic inverter may include an inverter circuit, multiple transformer circuits, a collection circuit and a control circuit. A transformer circuit may include at least one switch tube. Here, one end of each transformer circuit can be used to respectively connect to each group of photovoltaic panels in multiple groups of photovoltaic panels, and the other end of each transformer circuit can be used to connect to the load through the inverter circuit after being connected in parallel to the BUS bus. The collection circuit connects each transformer circuit, the BUS bus and the control circuit. The control circuit connects the switch tubes in each transformer circuit. The method may include:

[0018] Detect the input voltage of the target transformer circuit, the input current of the target transformer circuit, and the voltage of the BUS bus, wherein the target transformer circuit is any one or any several transformer circuits among the multiple transformer circuits. Adjust the current threshold of the target transformer circuit based on the input voltage of the target transformer circuit and the voltage of the BUS bus. When the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, adjust the duty cycle of the switch tube in the target transformer circuit to adjust the conduction or shutdown of the switch tube in the target transformer circuit to reduce the current or input power of the target transformer circuit.

[0019] In the present application, the photovoltaic panel can be used as a DC power source to connect the load through a photovoltaic inverter, and the photovoltaic inverter can convert the DC power provided by the photovoltaic panel into AC power and provide it to the load. Here, the photovoltaic inverter may include an inverter circuit and multiple transformer circuits, and the DC power source may be composed of multiple groups of photovoltaic panels (each group of photovoltaic panels may include one photovoltaic panel or multiple photovoltaic panels), and each group of photovoltaic panels may be connected to the inverter circuit through a transformer circuit. The transformer circuit can convert the DC voltage provided by the photovoltaic panel into a BUS bus voltage, and then convert the DC power into AC power through the inverter circuit, so that the AC voltage output by the photovoltaic inverter can adapt to loads of various voltage ranges. In an application scenario involving multiple groups of photovoltaic panels, due to the differences between the photovoltaic panels of each group (for example, different lengths, different shapes, different light intensities, etc.), when the difference between the output voltage of the photovoltaic panel connected to a certain transformer circuit (that is, the input voltage of the transformer circuit) and the BUS bus voltage is too large, the input current in the transformer circuit is usually also relatively large, and then, the components in the transformer circuit (for example, the switch tube in the transformer circuit) may fail or be damaged due to overvoltage (voltage difference is too large), overcurrent (current is too large) or overheating (temperature is too high). Here, the photovoltaic inverter may also include a control circuit and a collection circuit, and the collection circuit can detect the power supply parameters of the photovoltaic inverter (for example, the input voltage and / or output voltage of the transformer circuit, the input current and / or output current of the transformer circuit, the temperature of the transformer circuit, the BUS bus voltage and / or current, the input voltage and / or output voltage of the inverter circuit, the input current and / or output current of the inverter circuit, the temperature of the inverter circuit, etc.). Here, the control circuit can judge the working state of the photovoltaic inverter based on the power supply parameters of the photovoltaic inverter. Here, taking the one (or more) transformer circuits that the control circuit needs to control as the target transformer circuit as an example, the control circuit can adjust the current threshold of the target transformer circuit based on the input voltage of the target transformer circuit and the voltage of the BUS bus. After obtaining the current threshold of the target transformer circuit, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, in order to protect the working safety of the transformer circuit, the control circuit can adjust the duty cycle of the switch tube in the target transformer circuit (for example, reduce the duty cycle of the switch tube in the target transformer circuit) to adjust the conduction or shutdown of the switch tube in the target transformer circuit, thereby reducing the current or input power of the target transformer circuit.

[0020] By adopting the present application, the photovoltaic inverter can adjust the duty cycle of the switch tube through the control circuit to reduce the input power of the transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, thereby improving the stability and power supply efficiency of the photovoltaic inverter while ensuring power supply safety. The structure is simple, the method is simple, and the applicability is strong.

[0021] In combination with the second aspect, in a first possible implementation manner, adjusting the current threshold of the target voltage transformation circuit based on the input voltage of the target voltage transformation circuit and the voltage of the BUS bus may include:

[0022] The temperature of the target transformer circuit is detected. When the temperature of the target transformer circuit is greater than or equal to the temperature threshold, the current threshold of the target transformer circuit is adjusted to a first current threshold based on the input voltage of the target transformer circuit and the voltage of the BUS bus.

[0023] It can be understood that the control circuit can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to control the input power (or input current) of the target transformer circuit. In other words, the control circuit can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to adjust the duty cycle of the switch tube in the target transformer circuit. For example, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, it can be considered that the target transformer circuit is in a working state where the input power needs to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively poor, and the risk of damage is greater if it continues to work). At this time, the control circuit needs to reduce the input current and / or input power of the target transformer circuit. Here, when the operating temperature of the switch tube in the target transformer circuit is different, even if the voltage difference borne by the switch tube is the same, the input current that the switch tube can withstand may be different. For example, when the operating temperature of the switch tube in the target transformer circuit is high (for example, the temperature of the target transformer circuit is greater than or equal to the temperature threshold), the control circuit can determine the maximum input current (for example, the first current threshold) that the switch tube in the target transformer circuit can withstand based on the voltage difference borne by the switch tube in the target transformer circuit (for example, the difference between the input voltage of the target transformer circuit and the voltage of the BUS bus). It should be noted that the value of the first current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when bearing different voltage differences), or it can be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage. For example, the photovoltaic inverter or the external central control system can calculate the relationship curve of the current threshold corresponding to the switch tube when bearing different voltage differences during the operation (or design) of the transformer circuit at a certain operating temperature or a certain operating temperature range (for example, in a first operating temperature range greater than or equal to the temperature threshold), and then the control circuit can obtain the first current threshold based on this relationship curve, which can be set according to the application scenario. It can be understood that the first current threshold here can be a current, can be a plurality of discrete currents, or can be a current interval composed of a plurality of discrete currents or continuous currents.

[0024] In the present application, when the operating temperature of the switch tube in the target transformer circuit is high (for example, the temperature of the target transformer circuit is greater than or equal to the temperature threshold), if the input current of the switch tube in the target transformer circuit is greater than or equal to the first current threshold, it means that the target transformer circuit is in a working state that needs to be adjusted. The control circuit can reduce the duty cycle of the switch tube in the target transformer circuit, thereby reducing the input power of the target transformer circuit to avoid damage to the components in the target transformer circuit due to overheating, thereby improving the safety of the target transformer circuit. At the same time, because the control circuit does not completely shut down the input power of the target transformer circuit, the transmission efficiency of the power is ensured on the basis of ensuring safety.

[0025] In combination with the first possible implementation manner of the second aspect, in a second possible implementation manner, after detecting the temperature of the target transformer circuit, the method further includes:

[0026] When the temperature of the target transformer circuit is lower than the temperature threshold, the current threshold of the target transformer circuit is adjusted to a second current threshold based on the input voltage of the target transformer circuit and the voltage of the BUS bus, wherein the second current threshold is greater than or equal to the first current threshold.

[0027] It can be understood that the control circuit can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to control the input power (or input current) of the target transformer circuit. In other words, the control circuit can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to adjust the duty cycle of the switch tube in the target transformer circuit. For example, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, it can be considered that the target transformer circuit is in a working state where the input power needs to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively poor, and the risk of damage is greater if it continues to work). At this time, the control circuit needs to reduce the input current and / or input power of the target transformer circuit. Here, when the operating temperature of the switch tube in the target transformer circuit is different, even if the voltage difference borne by the switch tube is the same, the input current that the switch tube can withstand may be different. For example, when the operating temperature of the switch tube in the target transformer circuit is low (for example, the temperature of the target transformer circuit is less than the temperature threshold), the control circuit can determine the maximum input current (for example, the second current threshold) that the switch tube in the target transformer circuit can withstand based on the voltage difference borne by the switch tube in the target transformer circuit (for example, the difference between the input voltage of the target transformer circuit and the voltage of the BUS bus). Here, the second current threshold is less than or equal to the first voltage threshold. It should be noted that the value of the second current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when they bear different voltage differences), and can also be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage. For example, a photovoltaic inverter or an external central control system can calculate the relationship curve of the current threshold corresponding to the switch tube when it bears different voltage differences during the operation (or design) of the transformer circuit at a certain operating temperature or a certain operating temperature range (for example, in a second operating temperature range that is less than the temperature threshold), and then the control circuit can obtain the second current threshold based on this relationship curve, which can be set specifically according to the application scenario. It can be understood that the second current threshold here can be a current, multiple discrete currents, or a current range composed of multiple discrete currents or continuous currents.

[0028] In the present application, when the operating temperature of the switch tube in the target transformer circuit is low (for example, the temperature of the target transformer circuit is less than the temperature threshold), if the input current of the switch tube in the target transformer circuit is greater than or equal to the second current threshold, it means that the target transformer circuit is in a working state that needs to be adjusted. The control circuit can reduce the duty cycle of the switch tube in the target transformer circuit, thereby reducing the input power of the target transformer circuit to avoid damage to the components in the target transformer circuit due to overheating, thereby improving the safety of the target transformer circuit. At the same time, because the control circuit does not completely shut down the input power of the target transformer circuit, the transmission efficiency of the power is ensured on the basis of ensuring safety.

[0029] In combination with the second possible implementation manner of the second aspect, in a third possible implementation manner, after adjusting the current threshold of the target voltage transformation circuit based on the input voltage of the target voltage transformation circuit and the voltage of the BUS bus, the method may further include:

[0030] When the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, a switching modulation signal is generated based on the input current of the target transformer circuit and the current threshold of the target transformer circuit, and the duty cycle of the switch tube in the target voltage circuit is controlled by the switching modulation signal to adjust the conduction or shutdown of the switch tube in the target transformer circuit.

[0031] Here, the control circuit (for example, a current regulation loop (for example, a proportional regulation circuit or a proportional integral regulation circuit) and a drive control circuit, or other circuits having a current regulation function and a drive control function) can generate a switch modulation signal based on the input current of the target transformer circuit and the current threshold of the target transformer circuit to control the duty cycle of the switch tube in the target transformer circuit. For example, the control circuit can generate a pulse width modulation, PWM wave or other signal as a switch modulation signal, or generate a drive pulse signal based on the PWM wave as a switch modulation signal. Here, the switch modulation signal can control the duty cycle of the switch tube in the target transformer circuit, thereby controlling the input current and / or input power of the target transformer circuit. For example, the control circuit can reduce the duty cycle of the switch tube in the target transformer circuit to reduce the input current of the target transformer circuit, thereby reducing the input power of the target transformer circuit. It can be understood that the control circuit provided in the present application can use discontinuous pulse width modulation (DPWM) wave as the switching modulation signal, and can also use other PWM waves (for example, sinusoidal pulse width modulation (SPWM) wave, third harmonic injection pulse width modulation (THIPWM) wave, carrier based space vector pulse width modulation (CBPWM) wave, etc.) as the switching modulation signal, and can also use the driving pulse signal generated based on these PWM waves as the switching modulation signal. It has a wide range of application scenarios and good control effect.

[0032] In combination with the second aspect or any possible implementation manner of the second aspect, in a fourth possible implementation manner, after adjusting the current threshold of the target voltage transformation circuit based on the input voltage of the target voltage transformation circuit and the voltage of the BUS bus, the method may further include:

[0033] When the input current of the target transformer circuit is less than the current threshold of the target transformer circuit, the duty cycle of the switch tube in the target transformer circuit is adjusted to adjust the conduction or cutoff of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power.

[0034] Here, when the input current of the target transformer circuit is less than the current threshold of the target transformer circuit (for example, the third current threshold), it can be considered that the target transformer circuit is in a working state where the input power does not need to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively safe and the risk of damage is relatively small). At this time, the control circuit can adjust the duty cycle of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power (for example, so that the photovoltaic panel connected to the target transformer circuit operates at the maximum power point). Here, the value of the third current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when they bear different voltage differences), or it can be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage. For example, the photovoltaic inverter or the external central control system can calculate the relationship curve of the current threshold corresponding to the switch tube when it bears different voltage differences during the operation (or design) of the transformer circuit at a certain operating temperature or a certain operating temperature interval (for example, in a first operating temperature interval greater than or equal to the temperature threshold, or in a second operating temperature interval less than the temperature threshold), and then the control circuit can obtain the third current threshold based on this relationship curve, which can be set according to the application scenario. It can be understood that the third current threshold here can be a current, a plurality of discrete currents, or a current interval composed of a plurality of discrete currents or continuous currents. For example, in a first operating temperature interval greater than or equal to the temperature threshold, the third current threshold can be less than or equal to the first current threshold. For another example, in a second operating temperature interval less than the temperature threshold, the third current threshold can be less than or equal to the second current threshold. When the third voltage threshold is less than the first current threshold (or the second current threshold), the photovoltaic inverter can avoid repeatedly reducing or increasing the input power of the target transformer circuit through the control circuit when the input current of the target transformer circuit is not stably less than the first current threshold (or the second current threshold). That is to say, when the third voltage threshold is less than the first current threshold (or the second current threshold), the photovoltaic inverter can put the target transformer circuit in an operating state where the input power does not need to be reduced (or the working environment of the switch tube in the target transformer circuit is safer and the risk of damage is lower) after the input current of the target transformer circuit is stable (for example, stably less than the third current threshold), and the target transformer circuit is in an operating state where the input power does not need to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is safer and the risk of damage is lower. At this time, the control circuit can adjust the duty cycle of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power (for example, so that the photovoltaic panel connected to the target transformer circuit operates at the maximum power point), thereby improving the power supply efficiency.

[0035] In combination with the second aspect or any possible implementation manner of the second aspect, in a fifth possible implementation manner, the inverter circuit may include a switch tube, and after detecting the input voltage of the target transformer circuit, the input current of the target transformer circuit, and the voltage of the BUS bus, the method may further include:

[0036] When the voltage of the BUS bus is greater than or equal to the bus voltage threshold, the duty cycle of the switch tube in the inverter circuit is adjusted to adjust the on or off of the switch tube in the inverter circuit to reduce the output power of the inverter circuit.

[0037] It is understood that the control circuit can determine the working state of the photovoltaic inverter in a variety of ways, and then determine whether it is necessary to control the output power (or output current) of the photovoltaic inverter (for example, the inverter circuit). For example, when the voltage of the BUS bus is greater than or equal to the bus voltage threshold, it can be considered that the inverter circuit is in a working state where the output power needs to be reduced (or in other words, the working environment of each component in the photovoltaic inverter is relatively harsh, and the risk of damage is relatively high if it continues to work). At this time, the control circuit needs to reduce the output current and / or output power of the inverter circuit. It is understood that the bus voltage threshold here can be a voltage, can be a plurality of discrete voltages, can be a voltage interval composed of a plurality of discrete voltages or a continuous voltage.

[0038] In the present application, when the voltage of the BUS is high (for example, the voltage of the BUS is greater than or equal to the bus voltage threshold), it indicates that the photovoltaic inverter is in a working state where the output power needs to be reduced. The control circuit can reduce the duty cycle of each switch tube in the inverter circuit, thereby reducing the output power of the inverter circuit to avoid damage to components in the photovoltaic inverter due to overheating, thereby further improving power supply safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of an application scenario of a photovoltaic inverter provided in an embodiment of the present application;

[0040] Figure 2 It is a schematic diagram of the layout scenario of the photovoltaic panels provided in the embodiment of the present application;

[0041] Figure 3 is a structural schematic diagram of a photovoltaic inverter provided in an embodiment of the present application;

[0042] Figure 4 It is a schematic diagram of the volt-ampere characteristics of the photovoltaic panel provided in the embodiment of the present application;

[0043] Figure 5 is a schematic diagram of a current threshold curve of a voltage transformer circuit provided in an embodiment of the present application;

[0044] Figure 6is another structural schematic diagram of a photovoltaic inverter provided in an embodiment of the present application;

[0045] Figure 7 is a schematic diagram of the structure of a photovoltaic system provided in an embodiment of the present application;

[0046] Figure 8 is a flow chart of a power control method provided by an embodiment of the present application;

[0047] Fig. 9 It is another flow chart of the power control method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] In the field of power electronics, the inverter circuit in the photovoltaic inverter is usually used to convert DC power into AC power so that the power can be transmitted between the power source and the load. For example, in the field of photovoltaic power supply, the photovoltaic inverter can convert the DC power output by the DC power source (for example, the photovoltaic panel) into AC power and provide it to the load or the power grid. Usually, the control circuit in the photovoltaic inverter (for example, the MPPT control circuit) controls the output current of the photovoltaic panel (that is, the input current of the photovoltaic inverter) according to the output voltage of the photovoltaic panel (that is, the input voltage of the photovoltaic inverter), so that the photovoltaic panel outputs power to the load at maximum power. In practical applications, the photovoltaic inverter usually converts the DC voltage provided by each group of photovoltaic panels into a DC bus voltage (for example, the voltage of each group of photovoltaic panels is stepped up and converted into a BUS bus voltage) through multiple transformer circuits, and then converts the DC power into AC power through the inverter circuit to adapt to the voltage of different loads. Due to the differences between the photovoltaic panels of each group (for example, different lengths, different light intensities, etc.), when the difference between the output voltage of the photovoltaic panels connected to a certain transformer circuit (that is, the input voltage of the transformer circuit) and the BUS voltage is too large, the input current in the transformer circuit is usually also relatively large, and then, the components in the transformer circuit (for example, the switch tube in the transformer circuit) may fail or be damaged due to overvoltage, overcurrent or overheating. Therefore, when the transformer circuit is working, it is necessary to control the input power (or input current and other parameters) of the transformer circuit to ensure the power supply safety of each component in the photovoltaic inverter.

[0049] The present application provides a photovoltaic inverter and a power control method, which can adjust the duty cycle of the switch tube through a control circuit to reduce the input power of the transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, thereby improving the stability and power supply efficiency of the photovoltaic inverter while ensuring power supply safety. The application has a simple structure, a simple method and strong applicability.

[0050] The photovoltaic inverter provided in the present application can be applicable to various application fields such as the field of new energy power generation, the field of peak and frequency regulation of traditional power generation, the field of power supply for important equipment, the field of new energy vehicles, etc., which can be specifically determined according to the actual application scenario and is not limited here. The photovoltaic inverter provided in the present application can be applicable to different power supply systems such as energy storage systems, uninterruptible power supply systems, motor drive systems, etc., which can be specifically determined according to the actual application scenario and is not limited here. The photovoltaic inverter provided in the present application can be adapted to different application scenarios, such as application scenarios for controlling inverters in a solar power supply environment, application scenarios for controlling inverters in a new energy power supply environment, or other application scenarios. The following will take the application scenario of controlling a photovoltaic inverter in a solar power supply environment as an example for explanation, and will not be repeated below.

[0051] See also Figure 1 , Figure 1 Schematic diagram of the application scenario of the photovoltaic inverter provided in the embodiment of the present application. Figure 1 As shown, the photovoltaic system includes a photovoltaic inverter 1, a power source 2 consisting of multiple groups of photovoltaic panels (for example, photovoltaic panel a-photovoltaic panel n) and a load 3, wherein the power source 2 can be connected to the load 3 via the photovoltaic inverter 1. In some feasible embodiments, the photovoltaic inverter 1 can convert the DC power provided by the power source 2 consisting of multiple groups of photovoltaic panels into AC power and provide it to the load. It can be understood that the power source 2 provided in the present application is suitable for powering base station equipment in remote areas where there is no mains power or the mains power is poor, or for powering household appliances (such as refrigerators, air conditioners, etc.) and other application scenarios for powering various types of electrical equipment. The specific power can be determined according to the actual application scenario and is not limited here. It can be further understood that, Figure 2 The load 3 in the figure may include a power grid, and the power grid here may include power-consuming devices or power transmission devices such as transmission lines, power transfer stations, communication base stations, or household appliances. Here, the photovoltaic inverter 1 includes an inverter circuit 11 and multiple transformer circuits (for example, transformer circuit a-transformer circuit n), and each group of photovoltaic panels can be connected to the inverter circuit 11 through a corresponding transformer circuit. The transformer circuit can convert the DC voltage provided by the photovoltaic panel into a BUS bus voltage, and then convert the DC power into AC power through the inverter circuit 11, so that the AC voltage output by the photovoltaic inverter can adapt to loads with a variety of voltage ranges.

[0052] In some feasible implementations, please combine Figure 2 , Figure 2 Schematic diagram of the layout of photovoltaic panels provided in the embodiment of the present application. Figure 2As shown, the gray part is the location where the photovoltaic panels are arranged (for example, the top of a house or building). In an application scenario including multiple groups of photovoltaic panels, due to the differences between the groups of photovoltaic panels (for example, Figure 2 As shown in parts (a), (b) and (c), the light intensity of the photovoltaic panels arranged on the top is different. Figure 2 As shown in parts (d), (e) and (f), the length and shape of the photovoltaic panels arranged on the top are different. When the difference between the output voltage of the photovoltaic panel connected to a certain transformer circuit (that is, the input voltage of the transformer circuit) and the BUS bus voltage is too large, the input current in the transformer circuit is usually also relatively large, and then, the components in the transformer circuit (for example, the switch tube in the transformer circuit) may fail or be damaged due to overvoltage (voltage difference is too large), overcurrent (current is too large) or overheating (temperature is too high). Therefore, when the photovoltaic inverter 1 is working, it is necessary to control the input power in the transformer circuit to ensure the power supply safety of each component in the photovoltaic inverter. Here, the photovoltaic inverter 1 may further include a control circuit 13 and a collection circuit 12, and the collection circuit 12 may detect the power supply parameters of the photovoltaic inverter (for example, the input voltage and / or output voltage of the transformer circuit, the input current and / or output current of the transformer circuit, the temperature of the transformer circuit, the BUS bus voltage and / or current, the input voltage and / or output voltage of the inverter circuit 11, the input current and / or output current of the inverter circuit 11, the temperature of the inverter circuit 11, etc.). Here, the control circuit 13 may determine the working state of the photovoltaic inverter based on the power supply parameters of the photovoltaic inverter. Here, taking the one (or more) transformer circuits that the control circuit 13 needs to control as the target transformer circuit as an example, the control circuit 13 may adjust the current threshold of the target transformer circuit based on the input voltage of the target transformer circuit and the voltage of the BUS bus. After obtaining the current threshold of the target transformer circuit, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, in order to protect the working safety of the transformer circuit, the control circuit 13 can adjust the duty cycle of the switch tube in the target transformer circuit (for example, reduce the duty cycle of the switch tube in the target transformer circuit) to adjust the conduction or shutdown of the switch tube in the target transformer circuit, thereby reducing the input power of the target transformer circuit, while ensuring the power supply safety, improving the stability and power supply efficiency of the photovoltaic inverter, with a simple structure, simple method and strong applicability.

[0053] The following will be combined Figures 3 to 9 The photovoltaic inverter provided in this application and its working principle are illustrated.

[0054] See also Figure 3 , Figure 3 Schematic diagram of a photovoltaic inverter provided in an embodiment of the present application. Figure 3As shown, the photovoltaic system includes a power supply, a photovoltaic inverter and a load. The photovoltaic inverter includes an inverter circuit 101, multiple voltage conversion circuits, multiple acquisition circuits and a control circuit 103. A voltage conversion circuit may include at least one switch tube. Here, in order to make the connection relationship in the legend more concise and clear, the drawings of this application integrate multiple acquisition circuits into one acquisition circuit module to show their connection relationship and detection relationship, and explain its working principle, such as Figure 3 In the figure, multiple acquisition circuits are exemplarily shown as acquisition circuit 102. In a specific implementation, the acquisition circuits in each figure can be divided into multiple acquisition circuits and arranged, which will not be repeated below. Here, one end of each transformer circuit can be used to respectively connect to each group of photovoltaic panels in a plurality of photovoltaic panels, and the other end of each transformer circuit can be used to connect to the load through the inverter circuit 101 after being connected in parallel to the BUS bus. The acquisition circuit 102 can be connected to the control circuit 103 and used to detect the voltage or current of multiple transformer circuits and the BUS bus. The control circuit 103 is connected to the switch tube in each transformer circuit. The acquisition circuit 102 here can be used to detect the input voltage of the target transformer circuit and the voltage of the BUS bus, wherein the target transformer circuit is any one or any several transformer circuits among the multiple transformer circuits. The control circuit 103 here can adjust the current threshold of the target transformer circuit based on the input voltage of the target transformer circuit and the voltage of the BUS bus. The control circuit 103 here can be used to adjust the duty cycle of the switch tube in the target transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, so as to adjust the conduction or shutdown of the switch tube in the target transformer circuit to reduce the current or input power of the target transformer circuit.

[0055] In the present application, the voltage conversion circuit may be a variety of circuits having a voltage conversion function. Figure 3In the example, only the transformer circuit is a BOOST boost circuit. Here, the BOOST boost circuit may include a switch tube, an inductor and a diode. One end of the inductor is connected to the power supply (ie, the photovoltaic panel), and the other end of the inductor is connected to the BUS bus through the switch tube and the diode. In some application scenarios, the BOOST circuit can reuse the bus capacitor connected in parallel between the BUS buses to stabilize the output voltage of the BOOST circuit through the bus capacitor. When the switch tube of the BOOST circuit is turned on, the power supply charges the inductor, and the BOOST circuit supplies power to the inverter circuit 101 (and the load) through the bus capacitor, while the diode prevents the electric energy at the bus capacitor from converging; when the switch tube of the BOOST circuit is disconnected, the power supply and the inductor charge the bus capacitor, and the BOOST circuit increases the input voltage to the voltage of the bus capacitor for output. It can be understood that when the switch tube voltage of the BOOST circuit is negligible, the input voltage Vin of the BOOST circuit, the output voltage Vout of the BOOST circuit, and the duty cycle N of the switch tube of the BOOST circuit satisfy: Vin / Vout=1 / (1-N). Here, the acquisition circuit 102 can detect the power supply parameters of the photovoltaic inverter (for example, the input voltage and / or output voltage of the transformer circuit, the input current and / or output current of the transformer circuit, the temperature of the transformer circuit, the BUS bus voltage and / or current, the input voltage and / or output voltage of the inverter circuit 101, the input current and / or output current of the inverter circuit 101, the temperature of the inverter circuit 101, etc.). At the same time, it can be understood that the control circuit 103 can determine the working state of the photovoltaic inverter based on the power supply parameters of the photovoltaic inverter. Here, taking the one (or more) transformer circuits that the control circuit 103 needs to control as the target transformer circuit as an example, the control circuit 103 can adjust the current threshold of the target transformer circuit based on the input voltage of the target transformer circuit and the voltage of the BUS bus. For details, please refer to the following. Figure 4 , Figure 4 Schematic diagram of the volt-ampere characteristics of the photovoltaic panel provided in the embodiment of the present application. Figure 4 As shown, after obtaining the current threshold of the target transformer circuit, it is assumed that the output parameters (such as output current and output voltage) of a group of photovoltaic panels connected to the target transformer circuit correspond to Figure 4Point B in the volt-ampere characteristic curve of the group of photovoltaic panels. When the output current Ib of the photovoltaic panel corresponding to point B (that is, the input current of the target transformer circuit) is less than the current threshold of the target transformer circuit, in order to ensure the power supply efficiency of the system, the control circuit 103 in the photovoltaic inverter (for example, the MPPT control circuit) will control the duty cycle of the switch tube in the target transformer circuit according to the output voltage of the photovoltaic panel (that is, the input voltage of the photovoltaic inverter) to adjust the on or off of the switch tube in the target transformer circuit, thereby increasing the output current of the photovoltaic panel to Ia corresponding to point A (that is, increasing the input current of the photovoltaic inverter to Ia), so that the photovoltaic panel outputs electrical energy at the maximum power (that is, the power shown at point A). Another example Figure 4 As shown, when the output current Ib of the photovoltaic panel corresponding to point B (that is, the input current of the target transformer circuit) is greater than or equal to the current threshold of the target transformer circuit, in order to protect the working safety of the transformer circuit, the control circuit 103 can adjust the duty cycle of the switch tube in the target transformer circuit (for example, reduce the duty cycle of the switch tube in the target transformer circuit) to adjust the on or off of the switch tube in the target transformer circuit, and reduce the output current of the photovoltaic panel to Ic corresponding to point C (that is, reduce the input current of the photovoltaic inverter to Ic), thereby reducing the input power of the target transformer circuit (that is, reduce the input power of the target transformer circuit to the power shown at point C).

[0056] By adopting the present application, the photovoltaic inverter can adjust the duty cycle of the switch tube through the control circuit 103 when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, thereby reducing the input power of the transformer circuit, thereby improving the stability and power supply efficiency of the photovoltaic inverter while ensuring power supply safety. The structure is simple, the method is simple, and the applicability is strong.

[0057] In some feasible implementations, the acquisition circuit 102 can also be used to detect the temperature of the target transformer circuit. The control circuit 103 can also be used to adjust the current threshold of the target transformer circuit to the first current threshold based on the input voltage of the target transformer circuit and the voltage of the BUS bus when the temperature of the target transformer circuit is greater than or equal to the temperature threshold. It can be understood that the control circuit 103 can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to control the input power (or input current) of the target transformer circuit. In other words, the control circuit 103 can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to adjust the duty cycle of the switch tube in the target transformer circuit. For example, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, it can be considered that the target transformer circuit is in a working state where the input power needs to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively harsh, and the risk of damage is greater if it continues to work). At this time, the control circuit 103 needs to reduce the input current and / or input power of the target transformer circuit. Here, when the operating temperature of the switch tube in the target transformer circuit is different, even if the voltage difference that the switch tube bears is the same, the input current that the switch tube can withstand may be different. Figure 5 , Figure 5 Schematic diagram of the current threshold curve of the transformer circuit provided in the embodiment of the present application. Figure 5 As shown, the photovoltaic inverter or the external central control system can calculate the relationship curve of the current threshold Ith corresponding to the switch tube when it bears different voltage differences D(V) during the operation process (or design process) of the transformer circuit at a certain operating temperature or a certain operating temperature range (for example, in a first operating temperature range greater than or equal to the temperature threshold) as curve 1, and then the control circuit 103 can obtain the first current threshold based on this relationship curve. For example, when the operating temperature of the switch tube in the target transformer circuit is high (for example, the temperature of the target transformer circuit is greater than or equal to the temperature threshold), the control circuit 103 can determine the maximum input current (for example, the first current threshold) that the switch tube in the target transformer circuit can withstand based on the voltage difference borne by the switch tube in the target transformer circuit (for example, the difference between the input voltage of the target transformer circuit and the voltage of the BUS bus). It should be noted that the value of the first current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when bearing different voltage differences), or based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage, etc., and can be set specifically according to the application scenario. It can be understood that the first current threshold here can be a current, can be multiple discrete currents, can be a current interval composed of multiple discrete currents or continuous currents.

[0058] In the present application, when the operating temperature of the switch tube in the target transformer circuit is high (for example, the temperature of the target transformer circuit is greater than or equal to the temperature threshold), if the input current of the switch tube in the target transformer circuit is greater than or equal to the first current threshold, it means that the target transformer circuit is in a working state that needs to be adjusted. The control circuit 103 can reduce the duty cycle of the switch tube in the target transformer circuit, thereby reducing the input power of the target transformer circuit to avoid damage to the components in the target transformer circuit due to overheating, thereby improving the safety of the target transformer circuit. At the same time, because the control circuit 103 does not completely shut down the input power of the target transformer circuit, the transmission efficiency of the power is ensured on the basis of ensuring safety.

[0059] In some feasible implementations, the control circuit 103 can also be used to adjust the current threshold of the target transformer circuit to a second current threshold based on the input voltage of the target transformer circuit and the voltage of the BUS bus when the temperature of the target transformer circuit is less than the temperature threshold, wherein the second current threshold is greater than or equal to the first current threshold. It can be understood that the control circuit 103 can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to control the input power (or input current) of the target transformer circuit. In other words, the control circuit 103 can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to adjust the duty cycle of the switch tube in the target transformer circuit. For example, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, it can be considered that the target transformer circuit is in a working state where the input power needs to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively harsh, and the risk of damage is relatively high if it continues to work), at this time, the control circuit 103 needs to reduce the input current and / or input power of the target transformer circuit. Here, when the operating temperature of the switch tube in the target transformer circuit is different, even if the voltage difference borne by the switch tube is the same, the input current that the switch tube can withstand may be different. Figure 5As shown, the photovoltaic inverter or the external central control system can calculate the relationship curve of the current threshold Ith corresponding to the switch tube when it bears different voltage differences D(V) during the operation process (or design process) of the transformer circuit at a certain operating temperature or a certain operating temperature range (for example, in a second operating temperature range less than the temperature threshold) as curve 2, and then the control circuit 103 can obtain the second current threshold based on this relationship curve. For example, when the operating temperature of the switch tube in the target transformer circuit is low (for example, the temperature of the target transformer circuit is less than the temperature threshold), the control circuit 103 can determine the maximum input current (for example, the second current threshold) that the switch tube in the target transformer circuit can withstand based on the voltage difference borne by the switch tube in the target transformer circuit (for example, the difference between the input voltage of the target transformer circuit and the voltage of the BUS bus). Here, the second current threshold is less than or equal to the first voltage threshold. It should be noted that the value of the second current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when bearing different voltage differences), or based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage, etc., and can be set specifically according to the application scenario. It can be understood that the second current threshold here can be a current, multiple discrete currents, or a current interval composed of multiple discrete currents or continuous currents.

[0060] In the present application, when the operating temperature of the switch tube in the target transformer circuit is low (for example, the temperature of the target transformer circuit is less than the temperature threshold), if the input current of the switch tube in the target transformer circuit is greater than or equal to the second current threshold, it means that the target transformer circuit is in a working state that needs to be adjusted. The control circuit 103 can reduce the duty cycle of the switch tube in the target transformer circuit, thereby reducing the input power of the target transformer circuit to avoid damage to the components in the target transformer circuit due to overheating, thereby improving the safety of the target transformer circuit. At the same time, because the control circuit 103 does not completely shut down the input power of the target transformer circuit, the transmission efficiency of the power is ensured on the basis of ensuring safety.

[0061] In some feasible implementations, the control circuit 103 may also be used to generate a switch modulation signal based on the input current of the target transformer circuit and the current threshold of the target transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, and control the duty cycle of the switch tube in the target voltage circuit through the switch modulation signal to adjust the on or off of the switch tube in the target transformer circuit. Here, the control circuit 103 (for example, a current regulation loop (for example, a proportional regulation circuit or a proportional integral regulation circuit) and a drive control circuit 103, or other circuits having a current regulation function and a drive control function) can generate a switch modulation signal based on the input current of the target transformer circuit and the current threshold of the target transformer circuit to control the duty cycle of the switch tube in the target transformer circuit. For example, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, the control circuit 103 can generate a reference value less than the current threshold based on the current threshold of the target transformer circuit, and use the input current of the target transformer circuit as a variable to be adjusted, and generate a switch modulation signal to control the duty cycle of the switch tube in the target transformer circuit through the switch modulation signal, thereby adjusting the input current in the target transformer circuit to less than the current threshold of the target transformer circuit (i.e., the aforementioned reference value). Here, the control circuit 103 can generate a pulse width modulation, PWM wave or other signal as a switch modulation signal, or generate a drive pulse signal based on the PWM wave as a switch modulation signal. Here, the switch modulation signal can control the duty cycle of the switch tube in the target transformer circuit, thereby controlling the input current and / or input power of the target transformer circuit. For example, the control circuit 103 can reduce the duty cycle of the switch tube in the target transformer circuit to reduce the input current of the target transformer circuit, thereby reducing the input power of the target transformer circuit. It can be understood that the control circuit 103 provided in the present application can use a discontinuous pulse width modulation (DPWM) wave as a switching modulation signal, or other PWM waves (for example, a sinusoidal pulse width modulation (SPWM) wave, a third harmonic injection pulse width modulation (THIPWM) wave, a carrier based space vector pulse width modulation (CBPWM) wave, etc.) as a switching modulation signal, and can also use a driving pulse signal generated based on these PWM waves as a switching modulation signal, which has a wide range of application scenarios and good control effects.

[0062] In some feasible implementations, the control circuit 103 may also be used to adjust the duty cycle of the switch tube in the target transformer circuit when the input current of the target transformer circuit is less than the current threshold of the target transformer circuit, so as to adjust the on or off of the switch tube in the target transformer circuit, so that the input power of the target transformer circuit is maintained at the maximum target input power. Figure 4 , after obtaining the current threshold of the target transformer circuit, it is assumed that the output parameters (such as output current and output voltage) of a group of photovoltaic panels connected to the target transformer circuit correspond to Figure 4 Point B in the volt-ampere characteristic curve of the group of photovoltaic panels in the target transformer circuit. When the output current Ib of the photovoltaic panel corresponding to point B (that is, the input current of the target transformer circuit) is less than the current threshold of the target transformer circuit (for example, the third current threshold), it can be considered that the target transformer circuit is in a working state where the input power does not need to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively safe and the risk of damage is relatively small). At this time, the control circuit 103 can adjust the duty cycle of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power (for example, so that the photovoltaic panel connected to the target transformer circuit operates at the maximum power point). Here, the value of the third current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when bearing different voltage differences), or it can be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage. For example, the photovoltaic inverter or the external central control system can calculate the relationship curve of the current threshold corresponding to the switch tube when it bears different voltage differences during the operation process (or design process) of the transformer circuit at a certain operating temperature or a certain operating temperature range (for example, in a first operating temperature range greater than or equal to the temperature threshold, or in a second operating temperature range less than the temperature threshold), and then the control circuit 103 can obtain the third current threshold based on this relationship curve, which can be set according to the application scenario. It can be understood that the third current threshold here can be a current, a plurality of discrete currents, or a current range composed of a plurality of discrete currents or continuous currents. For example, in the first operating temperature range greater than or equal to the temperature threshold, the third current threshold can be less than or equal to the first current threshold. For another example, in the second operating temperature range less than the temperature threshold, the third current threshold can be less than or equal to the second current threshold.

[0063] It can be understood that when the third voltage threshold is less than the first current threshold (or the second current threshold), the photovoltaic inverter can avoid repeatedly reducing or increasing the input power of the target transformer circuit through the control circuit 103 when the input current of the target transformer circuit is not stably less than the first current threshold (or the second current threshold). That is to say, when the third voltage threshold is less than the first current threshold (or the second current threshold), the photovoltaic inverter can be in a working state where the target transformer circuit does not need to reduce the input power after the input current of the target transformer circuit is stable (for example, stably less than the third current threshold) (or in other words, the working environment of the switch tube in the target transformer circuit is safer and the risk of damage is smaller. At this time, the control circuit 103 can adjust the duty cycle of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power (for example, the photovoltaic panel connected to the target transformer circuit operates at the maximum power point), thereby improving the power supply efficiency.

[0064] In some feasible implementations, the inverter circuit may include a switch tube (for example, a multi-level inverter circuit and its topology circuit). Figure 6 , Figure 6 is another structural schematic diagram of the photovoltaic inverter provided in the embodiment of the present application. Figure 6 As shown, the inverter circuit 201 includes 2 capacitors connected in series, 4 switch tubes connected in series and 2 diodes connected in reverse series. Figure 3 The voltage conversion circuit, the acquisition circuit 202 and the control circuit 203 in Figure 3 The connection relationship and working principle of the transformer circuit, the acquisition circuit 102 and the control circuit 103 are the same, and will not be repeated here. Here, the control circuit 203 can also be used to adjust the duty cycle of the switch tube in the inverter circuit 201 when the voltage of the BUS bus is greater than or equal to the bus voltage threshold, so as to adjust the conduction or shutdown of the switch tube in the inverter circuit 201 to reduce the output power of the inverter circuit 201. It can be understood that the control circuit 203 can determine the working state of the photovoltaic inverter in a variety of ways, and then determine whether it is necessary to control the output power (or output current) of the photovoltaic inverter (for example, the inverter circuit 201). For example, when the voltage of the BUS bus is greater than or equal to the bus voltage threshold, it can be considered that the inverter circuit 201 is in a working state where the output power needs to be reduced (or in other words, the working environment of each component in the photovoltaic inverter is relatively bad, and the risk of damage is relatively high if it continues to work). At this time, the control circuit 203 needs to reduce the output current and / or output power of the inverter circuit 201. It can be understood that the bus voltage threshold here can be a single voltage, can be a plurality of discrete voltages, or can be a voltage interval consisting of a plurality of discrete voltages or continuous voltages.

[0065] In the present application, when the voltage of the BUS is high (for example, the voltage of the BUS is greater than or equal to the bus voltage threshold), it indicates that the photovoltaic inverter is in a working state where the output power needs to be reduced. The control circuit 203 can reduce the duty cycle of each switch tube in the inverter circuit 201, thereby reducing the output power of the inverter circuit 201 to avoid damage to components in the photovoltaic inverter due to overheating, thereby further improving power supply safety.

[0066] This application also provides a photovoltaic system. Please refer to Figure 7 , Figure 7 Schematic diagram of the structure of the photovoltaic system provided in the embodiment of the present application. Figure 7 As shown, the photovoltaic system may include a power source and a photovoltaic inverter. The photovoltaic inverter here is suitable for the above Figures 1 to 6 The photovoltaic inverter shown, Figure 7 Only Figure 3 The photovoltaic inverter shown is used as an example for illustration. It can be understood that Figure 7 The inverter circuit 301, the voltage conversion circuit, the acquisition circuit 302 and the control circuit 303 are the same as those described above. Figure 3 The connection mode and working principle of the inverter circuit 101, the voltage conversion circuit, the acquisition circuit 102 and the control circuit 103 are the same, and will not be repeated here. Figure 7 In the photovoltaic system shown, the load here can be a power grid, and the photovoltaic system can also include an on-grid and off-grid wiring device 305. The photovoltaic inverter can supply power to power-consuming equipment or power transmission equipment such as transmission lines, power transfer stations, batteries, communication base stations or household appliances in the power grid through the on-grid and off-grid wiring device 305.

[0067] In the present application, the photovoltaic inverter, photovoltaic system and photovoltaic power system have various and flexible composition modes of functional modules, which can adapt to different power supply environments, improve the diversity of application scenarios of the photovoltaic system and enhance the adaptability of the photovoltaic system. Figures 1 to 7 Any photovoltaic system or photovoltaic inverter shown can adjust the duty cycle of the switch tube through the control circuit to reduce the input power of the transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, thereby improving the stability and power supply efficiency of the photovoltaic inverter while ensuring power supply safety. The structure is simple, the method is simple, and the applicability is strong. For the convenience of description, the following will be Figure 3 The structure of the photovoltaic inverter shown is used to illustrate the power control method provided in the embodiment of the present application.

[0068] See also Figure 8 , Figure 8The control method provided by the present application is applicable to a photovoltaic system or a photovoltaic inverter. The photovoltaic system here may include an inverter circuit and a plurality of transformer circuits. One end of each transformer circuit is used to connect to a photovoltaic panel, and the other end of each transformer circuit is used to connect to a BUS bus in parallel and then connect to a load through an inverter circuit. Here, the photovoltaic system and photovoltaic inverter also include but are not limited to the above Figures 1 to 7 Any photovoltaic system or photovoltaic inverter in a photovoltaic system shown in FIG. Figure 8 As shown, the power control method provided by the present application includes the following steps:

[0069] S701: Detect the input voltage of the target transformer circuit, the input current of the target transformer circuit, and the voltage of the BUS bus.

[0070] S702: Adjusting a current threshold of the target voltage transformation circuit based on an input voltage of the target voltage transformation circuit and a voltage of the BUS bus.

[0071] S703: When the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, adjust the duty cycle of the switch tube in the target transformer circuit to adjust the conduction or shutdown of the switch tube in the target transformer circuit to reduce the current or input power of the target transformer circuit.

[0072] In the present application, the photovoltaic panel can be used as a DC power source to connect the load through a photovoltaic inverter, and the photovoltaic inverter can convert the DC power provided by the photovoltaic panel into AC power and provide it to the load. Here, the photovoltaic inverter may include an inverter circuit and multiple transformer circuits, and the DC power source may be composed of multiple groups of photovoltaic panels (each group of photovoltaic panels may include one photovoltaic panel or multiple photovoltaic panels), and each group of photovoltaic panels may be connected to the inverter circuit through a corresponding transformer circuit. The transformer circuit can convert the DC voltage provided by the photovoltaic panel into a BUS bus voltage, and then convert the DC power into AC power through the inverter circuit, so that the AC voltage output by the photovoltaic inverter can adapt to loads of various voltage ranges. In an application scenario involving multiple groups of photovoltaic panels, due to the differences between the photovoltaic panels of each group (for example, different lengths, different shapes, different light intensities, etc.), when the difference between the output voltage of the photovoltaic panels connected to a certain (or several) transformer circuits (that is, the input voltage of the transformer circuit) and the BUS bus voltage is too large, the input current in the transformer circuit is usually also relatively large, and then, the components in the transformer circuit (for example, the switch tube in the transformer circuit) may fail or be damaged due to overvoltage (voltage difference is too large), overcurrent (current is too large) or overheating (temperature is too high). Here, the photovoltaic inverter may also include a control circuit and a collection circuit, and the collection circuit can detect the power supply parameters of the photovoltaic inverter (for example, the input voltage and / or output voltage of the transformer circuit, the input current and / or output current of the transformer circuit, the temperature of the transformer circuit, the BUS bus voltage and / or current, the input voltage and / or output voltage of the inverter circuit, the input current and / or output current of the inverter circuit, the temperature of the inverter circuit, etc.). Here, the control circuit can judge the working state of the photovoltaic inverter based on the power supply parameters of the photovoltaic inverter. Here, taking the one (or more) transformer circuits that the control circuit needs to control as the target transformer circuit as an example, the control circuit can adjust the current threshold of the target transformer circuit based on the input voltage of the target transformer circuit and the voltage of the BUS bus. After obtaining the current threshold of the target transformer circuit, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, in order to protect the working safety of the transformer circuit, the control circuit can adjust the duty cycle of the switch tube in the target transformer circuit (for example, reduce the duty cycle of the switch tube in the target transformer circuit) to adjust the conduction or shutdown of the switch tube in the target transformer circuit, thereby reducing the current or input power of the target transformer circuit.

[0073] By adopting the present application, the photovoltaic inverter can adjust the duty cycle of the switch tube through the control circuit to reduce the input power of the transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, thereby improving the stability and power supply efficiency of the photovoltaic inverter while ensuring power supply safety. The structure is simple, the method is simple, and the applicability is strong.

[0074] For some possible implementations, please refer to Fig. 9 , Fig. 9 FIG. 1 is another flow chart of the power control method provided by the present application. Fig. 9 As shown, after detecting the input voltage of the target transformer circuit, the input current of the target transformer circuit and the voltage of the BUS bus in the aforementioned step S701, the control circuit (or photovoltaic inverter) may determine the current threshold of the target transformer circuit based on the input voltage of the target transformer circuit and the input current of the target transformer circuit. The power control method may further include the following steps:

[0075] S801: Detect the temperature of the target transformer circuit.

[0076] S802: Whether the temperature of the target transformer circuit is greater than or equal to the temperature threshold. If the judgment result is yes, then execute step S803; if the judgment result is no, then execute step S804.

[0077] It can be understood that the control circuit can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to control the input power (or input current) of the target transformer circuit. In other words, the control circuit can determine the working state of the target transformer circuit in a variety of ways, and then determine whether it is necessary to adjust the duty cycle of the switch tube in the target transformer circuit. For example, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, it can be considered that the target transformer circuit is in a working state where the input power needs to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively poor, and the risk of damage is greater if it continues to work). At this time, the control circuit needs to reduce the input current and / or input power of the target transformer circuit. Here, when the operating temperature of the switch tube in the target transformer circuit is different, even if the voltage difference borne by the switch tube is the same, the input current that the switch tube can withstand may be different.

[0078] S803: Based on the input voltage of the target voltage transformation circuit and the voltage of the BUS bus, adjust the current threshold of the target voltage transformation circuit to a first current threshold.

[0079] Here, when the operating temperature of the switch tube in the target transformer circuit is high (for example, the temperature of the target transformer circuit is greater than or equal to the temperature threshold), the control circuit can determine the maximum input current (for example, the first current threshold) that the switch tube in the target transformer circuit can withstand based on the voltage difference borne by the switch tube in the target transformer circuit (for example, the difference between the input voltage of the target transformer circuit and the voltage of the BUS bus). It should be noted that the value of the first current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when bearing different voltage differences), or it can be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage. For example, the photovoltaic inverter or the external central control system can calculate the relationship curve of the current threshold corresponding to the switch tube when bearing different voltage differences during the operation (or design) of the transformer circuit at a certain operating temperature or a certain operating temperature range (for example, in a first operating temperature range greater than or equal to the temperature threshold), and then the control circuit can obtain the first current threshold based on this relationship curve, which can be set according to the application scenario. It can be understood that the first current threshold here can be a current, can be a plurality of discrete currents, or can be a current interval composed of a plurality of discrete currents or continuous currents.

[0080] In the present application, when the operating temperature of the switch tube in the target transformer circuit is high (for example, the temperature of the target transformer circuit is greater than or equal to the temperature threshold), if the input current of the switch tube in the target transformer circuit is greater than or equal to the first current threshold, it means that the target transformer circuit is in a working state that needs to be adjusted. The control circuit can reduce the duty cycle of the switch tube in the target transformer circuit, thereby reducing the input power of the target transformer circuit to avoid damage to the components in the target transformer circuit due to overheating, thereby improving the safety of the target transformer circuit. At the same time, because the control circuit does not completely shut down the input power of the target transformer circuit, the transmission efficiency of the power is ensured on the basis of ensuring safety.

[0081] S804: Based on the input voltage of the target voltage transformation circuit and the voltage of the BUS bus, adjust the current threshold of the target voltage transformation circuit to a second current threshold.

[0082] Here, when the operating temperature of the switch tube in the target transformer circuit is low (for example, the temperature of the target transformer circuit is less than the temperature threshold), the control circuit can determine the maximum input current (for example, the second current threshold) that the switch tube in the target transformer circuit can withstand based on the voltage difference borne by the switch tube in the target transformer circuit (for example, the difference between the input voltage of the target transformer circuit and the voltage of the BUS bus). Here, the second current threshold is less than or equal to the first voltage threshold. It should be noted that the value of the second current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when they bear different voltage differences), and can also be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage. For example, a photovoltaic inverter or an external central control system can calculate the relationship curve of the current threshold corresponding to the switch tube when it bears different voltage differences during the operation (or design) of the transformer circuit at a certain operating temperature or a certain operating temperature range (for example, in a second operating temperature range that is less than the temperature threshold), and then the control circuit can obtain the second current threshold based on this relationship curve, which can be set specifically according to the application scenario. It can be understood that the second current threshold here can be a current, multiple discrete currents, or a current range composed of multiple discrete currents or continuous currents.

[0083] In the present application, when the operating temperature of the switch tube in the target transformer circuit is low (for example, the temperature of the target transformer circuit is less than the temperature threshold), if the input current of the switch tube in the target transformer circuit is greater than or equal to the second current threshold, it means that the target transformer circuit is in a working state that needs to be adjusted. The control circuit can reduce the duty cycle of the switch tube in the target transformer circuit, thereby reducing the input power of the target transformer circuit to avoid damage to the components in the target transformer circuit due to overheating, thereby improving the safety of the target transformer circuit. At the same time, because the control circuit does not completely shut down the input power of the target transformer circuit, the transmission efficiency of the power is ensured on the basis of ensuring safety.

[0084] S805: When the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, adjust the duty cycle of the switch tube in the target transformer circuit to adjust the conduction or shutdown of the switch tube in the target transformer circuit to reduce the current or input power of the target transformer circuit.

[0085] In some feasible embodiments, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, a switching modulation signal is generated based on the input current of the target transformer circuit and the current threshold of the target transformer circuit, and the duty cycle of the switch tube in the target voltage circuit is controlled by the switching modulation signal to adjust the conduction or shutdown of the switch tube in the target transformer circuit.

[0086] Here, the control circuit (for example, a current regulation loop (for example, a proportional regulation circuit or a proportional integral regulation circuit) and a drive control circuit, or other circuits having a current regulation function and a drive control function) can generate a switch modulation signal based on the input current of the target transformer circuit and the current threshold of the target transformer circuit to control the duty cycle of the switch tube in the target transformer circuit. For example, the control circuit can generate a pulse width modulation, PWM wave or other signal as a switch modulation signal, or generate a drive pulse signal based on the PWM wave as a switch modulation signal. Here, the switch modulation signal can control the duty cycle of the switch tube in the target transformer circuit, thereby controlling the input current and / or input power of the target transformer circuit. For example, the control circuit can reduce the duty cycle of the switch tube in the target transformer circuit to reduce the input current of the target transformer circuit, thereby reducing the input power of the target transformer circuit. It can be understood that the control circuit provided in the present application can use discontinuous pulse width modulation (DPWM) wave as the switching modulation signal, and can also use other PWM waves (for example, sinusoidal pulse width modulation (SPWM) wave, third harmonic injection pulse width modulation (THIPWM) wave, carrier based space vector pulse width modulation (CBPWM) wave, etc.) as the switching modulation signal, and can also use the driving pulse signal generated based on these PWM waves as the switching modulation signal. It has a wide range of application scenarios and good control effect.

[0087] In some feasible implementations, after adjusting the current threshold of the target voltage conversion circuit based on the input voltage of the target voltage conversion circuit and the voltage of the BUS bus in the aforementioned step S702 or S803 or S804, the method may further include:

[0088] When the input current of the target transformer circuit is less than the current threshold of the target transformer circuit, the duty cycle of the switch tube in the target transformer circuit is adjusted to adjust the conduction or cutoff of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power.

[0089] Here, when the input current of the target transformer circuit is less than the current threshold of the target transformer circuit (for example, the third current threshold), it can be considered that the target transformer circuit is in a working state where the input power does not need to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is relatively safe and the risk of damage is relatively small). At this time, the control circuit can adjust the duty cycle of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power (for example, so that the photovoltaic panel connected to the target transformer circuit operates at the maximum power point). Here, the value of the third current threshold can be determined based on the maximum input current of the switch tube in the target transformer circuit (for example, based on the nominal current corresponding to various types of switch tubes when they bear different voltage differences), or it can be determined based on the current threshold obtained by the photovoltaic inverter through acquisition, collection, reception, detection or storage. For example, the photovoltaic inverter or the external central control system can calculate the relationship curve of the current threshold corresponding to the switch tube when it bears different voltage differences during the operation (or design) of the transformer circuit at a certain operating temperature or a certain operating temperature interval (for example, in a first operating temperature interval greater than or equal to the temperature threshold, or in a second operating temperature interval less than the temperature threshold), and then the control circuit can obtain the third current threshold based on this relationship curve, which can be set according to the application scenario. It can be understood that the third current threshold here can be a current, a plurality of discrete currents, or a current interval composed of a plurality of discrete currents or continuous currents. For example, in a first operating temperature interval greater than or equal to the temperature threshold, the third current threshold can be less than or equal to the first current threshold. For another example, in a second operating temperature interval less than the temperature threshold, the third current threshold can be less than or equal to the second current threshold. When the third voltage threshold is less than the first current threshold (or the second current threshold), the photovoltaic inverter can avoid repeatedly reducing or increasing the input power of the target transformer circuit through the control circuit when the input current of the target transformer circuit is not stably less than the first current threshold (or the second current threshold). That is to say, when the third voltage threshold is less than the first current threshold (or the second current threshold), the photovoltaic inverter can put the target transformer circuit in an operating state where the input power does not need to be reduced (or the working environment of the switch tube in the target transformer circuit is safer and the risk of damage is lower) after the input current of the target transformer circuit is stable (for example, stably less than the third current threshold), and the target transformer circuit is in an operating state where the input power does not need to be reduced (or in other words, the working environment of the switch tube in the target transformer circuit is safer and the risk of damage is lower. At this time, the control circuit can adjust the duty cycle of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power (for example, so that the photovoltaic panel connected to the target transformer circuit operates at the maximum power point), thereby improving the power supply efficiency.

[0090] In some feasible embodiments, after detecting the input voltage of the target transformer circuit, the input current of the target transformer circuit, and the voltage of the BUS bus, the method may further include:

[0091] When the voltage of the BUS bus is greater than or equal to the bus voltage threshold, adjust the duty cycle of the switching tube in the inverter circuit to regulate the conduction or cutoff of the switching tube in the inverter circuit, so as to reduce the output power of the inverter circuit.

[0092] It can be understood that the control circuit can determine the working state of the photovoltaic inverter in various ways, and then determine whether it is necessary to control the output power (or output current) of the photovoltaic inverter (for example, the inverter circuit). For example, when the voltage of the BUS bus is greater than or equal to the bus voltage threshold, it can be considered that the inverter circuit is in a working state where the output power needs to be reduced (or in other words, the working environment of each component in the photovoltaic inverter is relatively harsh, and the risk of damage is relatively high if it continues to work). At this time, the control circuit needs to reduce the output current and / or output power of the inverter circuit. It can be understood that the bus voltage threshold here can be a voltage, can be multiple discrete voltages, or can be a voltage range composed of multiple discrete voltages or continuous voltages.

[0093] It can be understood that when the voltage of the BUS bus is relatively high (for example, the voltage of the BUS bus is greater than or equal to the bus voltage threshold), it indicates that the photovoltaic inverter is in a working state where the output power needs to be reduced. The control circuit can reduce the duty cycle of each switching tube in the inverter circuit, thereby reducing the output power of the inverter circuit, so as to avoid damage to the components in the photovoltaic inverter due to overheating and further improve the power supply safety.

[0094] In the present application, when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, the photovoltaic inverter can adjust the duty cycle of the switching tube through the control circuit to reduce the input power of the transformer circuit, while ensuring power supply safety, improving the stability and power supply efficiency of the photovoltaic inverter, with a simple structure, a simple method, and strong applicability.

[0095] As described above, the above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A photovoltaic inverter, It is characterized in that The photovoltaic inverter includes an inverter circuit, multiple voltage conversion circuits, multiple acquisition circuits and a controller, and one of the voltage conversion circuits includes at least one switch tube; One end of each of the transformer circuits is used to be connected to each group of photovoltaic panels in the plurality of photovoltaic panels, and the other end of each of the transformer circuits is used to be connected in parallel to the BUS bus. The inverter circuit is used to be connected between the BUS bus and the load. The multiple acquisition circuits are used to detect the input voltage of the target transformer circuit, the voltage of the BUS bus and the temperature of the target transformer circuit, wherein the target transformer circuit is any one or any several transformer circuits among the multiple transformer circuits; The controller is used to control the on or off of the switch tubes in each of the transformer circuits; The controller is further configured to: when the input current of the target transformer circuit is greater than or equal to a current threshold, adjust the duty cycle of the switch tube in the target transformer circuit to adjust the on or off state of the switch tube in the target transformer circuit to reduce the input power of the target transformer circuit; The controller is further configured to adjust the current threshold value according to a voltage difference value of the target transformer circuit or a temperature of the target transformer circuit, wherein the voltage difference value is an absolute value of a difference between an input voltage of the target transformer circuit and a bus voltage of the BUS, including: If the voltage difference at the first moment is smaller than the voltage difference at the second moment, the current threshold at the second moment is adjusted to be smaller than the current threshold at the first moment, and the second moment is later than the first moment; or, If the temperature of the target transformer circuit at the first moment is lower than the temperature of the target transformer circuit at the second moment, the current threshold at the second moment is adjusted to be lower than the current threshold at the first moment.

2. The photovoltaic inverter according to claim 1, It is characterized in that The control circuit is also used to generate a switching modulation signal based on the input current of the target transformer circuit and the current threshold of the target transformer circuit when the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, and control the conduction or shutdown of the switch tube in the target transformer circuit through the switching modulation signal to adjust the duty cycle of the switch tube in the target voltage circuit.

3. The photovoltaic inverter according to any one of claims 1 to 2, It is characterized in that The control circuit is also used to adjust the conduction or shutoff of the switch tube in the target transformer circuit when the input current of the target transformer circuit is less than the current threshold of the target transformer circuit, so as to adjust the duty cycle of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power.

4. The photovoltaic inverter according to any one of claims 1 to 3, It is characterized in that The inverter circuit includes a switch tube, and the control circuit is also used to adjust the duty cycle of the switch tube in the inverter circuit when the voltage of the BUS bus is greater than or equal to the bus voltage threshold, so as to adjust the conduction or shutdown of the switch tube in the inverter circuit to reduce the output power of the inverter circuit.

5. A control method for a photovoltaic inverter, It is characterized in that The control method is applicable to a photovoltaic inverter, wherein the photovoltaic inverter comprises an inverter circuit and a plurality of transformer circuits. One end of each transformer circuit is used to connect to each group of photovoltaic panels in a plurality of groups of photovoltaic panels, and the other end of each transformer circuit is used to connect to a BUS bus in parallel and then connect to a load through the inverter circuit. The method includes: Detecting an input voltage of a target transformer circuit, an input current of the target transformer circuit, a voltage of the BUS bus, and a temperature of the target transformer circuit, wherein the target transformer circuit is any one or several transformer circuits among the multiple transformer circuits; When the input current of the target transformer circuit is greater than or equal to the current threshold, the duty cycle of the switch tube in the target transformer circuit is adjusted to adjust the on or off of the switch tube in the target transformer circuit to reduce the input power of the target transformer circuit; and, The current threshold is adjusted according to the voltage difference of the target transformer circuit or the temperature of the target transformer circuit, wherein the voltage difference is the absolute value of the difference between the input voltage of the target transformer circuit and the bus voltage of the BUS, including: If the voltage difference at the first moment is smaller than the voltage difference at the second moment, the current threshold at the second moment is adjusted to be smaller than the current threshold at the first moment, and the second moment is later than the first moment; or, If the temperature of the target transformer circuit at the first moment is lower than the temperature of the target transformer circuit at the second moment, the current threshold at the second moment is adjusted to be lower than the current threshold at the first moment.

6. The control method according to claim 5, It is characterized in that When the input current of the target transformer circuit is greater than or equal to the current threshold of the target transformer circuit, a switch modulation signal is generated based on the input current of the target transformer circuit and the current threshold of the target transformer circuit, and the duty cycle of the switch tube in the target transformer circuit is controlled by the switch modulation signal to adjust the conduction or shutdown of the switch tube in the target transformer circuit.

7. The control method according to any one of claims 5 to 6, It is characterized in that When the input current of the target transformer circuit is less than the current threshold of the target transformer circuit, the duty cycle of the switch tube in the target transformer circuit is adjusted to adjust the conduction or shutdown of the switch tube in the target transformer circuit so that the input power of the target transformer circuit is maintained at the maximum target input power.

8. The control method according to any one of claims 5 to 7, It is characterized in that When the voltage of the BUS bus is greater than or equal to the bus voltage threshold, the duty cycle of the switch tube in the inverter circuit is adjusted to adjust the on or off of the switch tube in the inverter circuit to reduce the output power of the inverter circuit.

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