Power converter and overcurrent protection method therefor, and energy storage system

Abstract

The present application relates to the technical field of power electronics, and provides a power converter and an overcurrent protection method therefor, and an energy storage system. In the power converter, when a second voltage is greater than a first voltage, a controller can reduce alternating current flowing through an inductor in a filter circuit or send an alarm signal, and when the voltage of a direct current side of an inverter circuit is large, the controller can reduce a first voltage outputted by a voltage adjusting circuit. The second voltage is positively correlated with the current value of the alternating current flowing through the inductor, and therefore, when the second voltage is greater than the first voltage, overcurrent protection for the power converter can be achieved by reducing the alternating current flowing through the inductor or sending an alarm signal, thereby preventing components in the power converter from being damaged by large current. In addition, the larger the voltage of the direct current side of the inverter circuit is, the larger the voltage stress of a power transistor in the inverter circuit is, and therefore, when the voltage of the direct current side of the inverter circuit is large, the first voltage is reduced, that is, the overcurrent protection point is reduced, so that the voltage stress of the power transistor in the inverter circuit can be reduced.

Description

Power converter, overcurrent protection method thereof, and energy storage system

[0001] This application claims priority to Chinese patent application number 202410316801.2, filed on March 19, 2024, entitled “Power converter, overcurrent protection method thereof, and energy storage system”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of power electronics technology, and in particular to a power converter and an overcurrent protection method thereof, and an energy storage system. Background Art

[0003] An energy storage system generally includes an energy storage battery and a power converter. The power converter can convert direct current (DC) provided by the energy storage battery into alternating current (AC) and output the AC to a load to power the load.

[0004] However, some factors (such as abnormal voltage and high temperature) can cause large inrush currents in the power converter, resulting in abnormal overcurrent in the power converter. This overcurrent can damage components in the power converter, such as burning out the power transistors in the power converter. Summary of the Invention

[0005] The present application provides a power converter and an overcurrent protection method and an energy storage system thereof, which can solve the problem that the power converter is prone to overcurrent in the related art.

[0006] In a first aspect, a power converter is provided, which includes an inverter circuit, a filter circuit, a voltage regulation circuit and a controller, wherein the inverter circuit is used to convert direct current from a photovoltaic component or an energy storage battery into alternating current, the filter circuit is used to filter the ripple of the alternating current output by the inverter circuit, and the voltage regulation circuit is used to output a first voltage with a variable voltage value; when the voltage on the DC side of the inverter circuit is greater than or equal to a set voltage threshold, the controller is used to reduce the first voltage; when the first voltage is less than a second voltage, the controller is used to reduce the alternating current flowing through the inductor in the filter circuit or issue an alarm signal, and the second voltage is positively correlated with the current value of the alternating current flowing through the inductor in the filter circuit.

[0007] In the power converter provided by the present application, because the controller can reduce the AC current flowing through the inductor in the filter circuit or issue an alarm signal when the second voltage is greater than the first voltage, and because the second voltage increases with the current value of the AC current flowing through the inductor in the filter circuit, the power converter can be promptly protected from overcurrent, preventing high current from damaging components in the power converter. Furthermore, because the voltage regulation circuit can output a first voltage with a variable voltage value, the first voltage representing the overcurrent protection point is flexibly adjustable, providing greater flexibility in overcurrent protection. Furthermore, because the controller can also reduce the first voltage output by the voltage regulation circuit when the voltage on the DC side of the inverter circuit is high, thereby lowering the overcurrent protection point, the current peak can be indirectly reduced, thereby achieving the purpose of reducing the voltage stress of the power transistors in the inverter circuit.

[0008] Optionally, the voltage regulation circuit may include a switching tube, a first resistor, a second resistor and a capacitor. The collector of the switching tube can be connected to the power supply end through the first resistor and the second resistor connected in series, the emitter of the switching tube can be grounded, the capacitor can be connected in parallel between the series connection point of the first resistor and the second resistor and the emitter of the switching tube, the series connection point of the first resistor and the second resistor and the base of the switching tube can be connected to the controller, and the first voltage can be negatively correlated with the duty cycle of the switching tube.

[0009] In the solution provided in this application, when the duty cycle of the switch tube increases, the first voltage can be increased accordingly; when the duty cycle of the switch tube decreases, the first voltage can be decreased accordingly. Thus, the controller can control the voltage regulation circuit to output a variable first voltage by adjusting the duty cycle of the switch tube. In addition, based on the circuit structure of the voltage regulation circuit, it can be seen that the duty cycle of the switch tube can control the on and off of the switch tube, thereby changing the charging and discharging time of the capacitor, achieving the purpose of linearly regulating the first voltage, that is, achieving the purpose of dynamically adjusting the overcurrent protection point.

[0010] Optionally, when the voltage on the DC side of the inverter circuit is greater than or equal to a set voltage threshold, the controller can be used to increase the duty cycle of the switch tube to reduce the first voltage.

[0011] That is, the controller can reduce the first voltage output by the voltage regulation circuit by increasing the duty cycle of the switch tube in the voltage regulation circuit.

[0012] Optionally, the controller may be configured to increase the duty cycle of the switch tube from a first duty cycle to a second duty cycle, and then reduce the second duty cycle to a third duty cycle, and the third duty cycle may be greater than the first duty cycle.

[0013] In the solution provided in the present application, when the controller increases the first duty cycle to the third duty cycle, that is, when the controller needs to increase the duty cycle, the duty cycle can be first increased to a second duty cycle that is greater than the third duty cycle, and then reduced to the third duty cycle. Because the larger the duty cycle, the higher the efficiency of discharging the capacitor in the voltage regulation circuit, by first adjusting the duty cycle to a larger value, the efficiency of the voltage regulation circuit in regulating the first voltage can be effectively improved, and the controller can then perform overcurrent protection on the power converter more quickly, resulting in a better overcurrent protection effect.

[0014] Optionally, the power converter may further include a sampling circuit and a comparison circuit. The sampling circuit may be used to sample the alternating current flowing through the inductor in the filter circuit and convert the alternating current into a second voltage. The output end of the sampling circuit may be connected to the negative phase input end of the comparison circuit, the output end of the voltage regulation circuit may be connected to the positive phase input end of the comparison circuit, and the output end of the comparison circuit may be connected to the controller.

[0015] That is, the sampling circuit can sample the AC current flowing through the inductor in the filter circuit to convert it into a second voltage. Furthermore, the comparison circuit can accurately and quickly compare the second voltage with the first voltage to instruct the controller to provide better overcurrent protection for the power converter.

[0016] Optionally, the power converter may also include a DC / DC conversion circuit, which can be used to change the voltage of the DC power from the photovoltaic component or the energy storage battery, and output the transformed DC power to the inverter circuit. The voltage on the DC side of the inverter circuit may include the voltage at the input end of the DC / DC conversion circuit.

[0017] In the solution provided in this application, the power converter may also include a DC / DC conversion circuit connected between the photovoltaic module / energy storage battery and the inverter circuit. On this basis, the voltage on the DC side of the inverter circuit may refer to the voltage received at the input end of the DC / DC conversion circuit, that is, the voltage of the DC power from the photovoltaic module or energy storage battery, which can better reflect the current input voltage operating condition of the power converter. Of course, the voltage on the DC side of the inverter circuit may also be the voltage after the DC / DC conversion circuit converts the voltage of the DC power from the photovoltaic module or energy storage battery.

[0018] Optionally, the controller may be configured to reduce the duty cycle of the power transistor in the inverter circuit to reduce the AC current flowing through the inductor in the filter circuit.

[0019] That is, the controller can reduce the conduction time of the power tube by reducing the duty cycle of the power tube in the inverter circuit, thereby reducing the AC power output by the inverter circuit, that is, reducing the AC power flowing through the inductor in the filter circuit, and achieving better overcurrent protection.

[0020] Optionally, the power converter may further include a signal processing circuit, which may be configured to perform at least one of amplification, filtering, and voltage stabilization on the second voltage, and output the processed second voltage to the controller.

[0021] By providing a signal processing circuit to perform processing such as amplification, filtering, and / or voltage stabilization on the second voltage before outputting it to the controller, the reliability of the output second voltage can be ensured. Furthermore, the controller can reliably detect the magnitude of the first and second voltages and reliably provide overcurrent protection to the power converter when the second voltage is greater than the first voltage, achieving a more effective overcurrent protection.

[0022] In a second aspect, a method for overcurrent protection of a power converter is provided, the method comprising: when the voltage on the DC side of the inverter circuit in the power converter is greater than or equal to a set voltage threshold, reducing a first voltage, the first voltage being the voltage output by the voltage regulation circuit in the power converter, the inverter circuit being used to convert DC power from a photovoltaic module or an energy storage battery into AC power; when the first voltage is less than a second voltage, reducing the AC power flowing through the inductor included in the filter circuit in the power converter or issuing an alarm signal, the second voltage being positively correlated with the current value of the AC power flowing through the inductor in the filter circuit, the filter circuit being connected to the inverter circuit and being used to filter the ripple of the AC power output by the inverter circuit.

[0023] In a third aspect, an energy storage system is provided, which includes an energy storage battery and a power converter as provided in the first aspect, wherein the energy storage battery is used to provide direct current to the power converter, and the power converter is used to convert the direct current into alternating current and output the converted alternating current to a load to power the load.

[0024] In summary, the present application provides a power converter, an overcurrent protection method therefor, and an energy storage system. In the solution provided herein, the power converter includes an inverter circuit, a filter circuit, a voltage regulator circuit, and a controller. The controller is capable of reducing the AC current flowing through the inductor of the filter circuit or issuing an alarm signal when the second voltage is greater than the first voltage, and is capable of reducing the first voltage output by the voltage regulator circuit when the voltage on the DC side of the inverter circuit is high. Because the second voltage is positively correlated with the current value of the AC current flowing through the inductor of the filter circuit, by reducing the AC current flowing through the inductor of the filter circuit or issuing an alarm signal when the second voltage is greater than the reference first voltage, overcurrent protection can be implemented for the power converter, preventing high current from damaging components within the power converter. Furthermore, because a higher voltage on the DC side of the inverter circuit increases the voltage stress on the power transistors within the inverter circuit, by reducing the first voltage when the DC side voltage of the inverter circuit is high, that is, by lowering the overcurrent protection point, the voltage stress on the power transistors within the inverter circuit can be correspondingly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a schematic diagram of a working scenario of a power converter provided in an embodiment of the present application;

[0026] FIG2 is a schematic structural diagram of a power converter provided in an embodiment of the present application;

[0027] FIG3 is a schematic structural diagram of another power converter provided in an embodiment of the present application;

[0028] FIG4 is a schematic structural diagram of another power converter provided in an embodiment of the present application;

[0029] FIG5 is a schematic structural diagram of another power converter provided in an embodiment of the present application;

[0030] FIG6 is a schematic diagram of the circuit structure of a voltage regulation circuit in a power converter provided in an embodiment of the present application;

[0031] FIG7 is a schematic diagram of a duty cycle of a switch tube in a voltage regulation circuit provided in an embodiment of the present application;

[0032] FIG8 is a schematic diagram of an operating mode of a voltage regulation circuit provided in an embodiment of the present application;

[0033] FIG9 is a schematic diagram of an operating mode of another voltage regulation circuit provided in an embodiment of the present application;

[0034] FIG10 is a schematic diagram of adjusting the duty cycle of a switch tube in a voltage regulation circuit provided by an embodiment of the present application;

[0035] FIG11 is a schematic diagram of another embodiment of the present application for adjusting the duty cycle of a switch tube in a voltage regulation circuit;

[0036] FIG12 is a flow chart of an overcurrent protection method for a power converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] The power converter and its overcurrent protection method and energy storage system provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings. First, the key terms involved in the embodiments of the present application are introduced.

[0038] Overcurrent protection (OCP) is a protection method that provides overcurrent protection to the power converter when the AC current flowing through the power inductor in the power converter exceeds the current threshold, that is, when an abnormal overcurrent occurs in the power converter.

[0039] Overcurrent point: The current threshold referenced during overcurrent protection, also known as the overcurrent protection point.

[0040] Dynamic overcurrent: An overcurrent protection mode in which the overcurrent protection point can be flexibly and dynamically adjusted according to actual conditions.

[0041] Voltage stress: The highest voltage or voltage peak that occurs during the switching process of the power tube included in the power converter, also known as high voltage stress.

[0042] It's understandable that the high-voltage stress on power tubes comes from two main sources: First, because the peak voltage of the power tube is superimposed on the input voltage received by the power converter (e.g., the voltage of the DC power provided by the energy storage battery), the higher the input voltage, the greater the peak voltage of the power tube. Second, because the current when the power tube is turned off is the current value of the alternating current (AC) flowing through the power inductor, the greater the peak current value (i.e., the inductor current peak), the greater the peak voltage of the power tube. In other words, one aspect is the input high-voltage operating condition; the other is the inductor current peak.

[0043] It's also understandable that there are two primary factors affecting the inductor current peak: First, because the inductor current peak is superimposed on the current threshold, the higher the current threshold, the larger the inductor current peak. Second, power converters often employ a frequency-increasing, inductance-reducing design (i.e., increasing the operating frequency and reducing the inductor's inductance) to reduce design costs. However, after reducing the inductance, it was discovered that for high-voltage input conditions, the inductor current peak significantly increases due to the inherent time delay of the overcurrent protection. Specifically, the first factor is the overcurrent protection point; the second is the inherent delay of the overcurrent protection, which is the duration of the inductor current increase.

[0044] Therefore, under the premise of a fixed overcurrent protection time, the overcurrent protection point can be adjusted to reduce the inductor current peak, thereby further reducing the voltage stress of the power tube. Currently, common overcurrent protection methods include hardware overcurrent protection and software overcurrent protection.

[0045] As the name implies, hardware overcurrent protection refers to the use of hardware circuits to implement overcurrent protection, and software overcurrent protection refers to the use of code to design a protection program to implement overcurrent protection. In addition, the current hardware overcurrent protection methods include the following embodiments: (1) Changing the overcurrent protection point by changing the resistance value before the power converter is powered on. (2) Implementing on-off control based on the level to change the circuit structure or the voltage division relationship in the circuit, thereby changing the overcurrent protection point. (3) Adjusting the overcurrent protection point based on the temperature coefficient curve. However, the first embodiment cannot dynamically adjust the overcurrent protection point after power-on, so the adjustment flexibility is poor. The second embodiment can only adjust the overcurrent protection point based on the level, and the state of the circuit structure is limited, so the overcurrent protection point cannot be linearly adjusted, and the adjustable range is limited. The third embodiment can only adjust the overcurrent protection point based on temperature, so the application scenario is limited and can only be used for overcurrent protection under overtemperature conditions. That is, the current hardware overcurrent protection method has the following problems: the overcurrent protection point has poor adjustability and a limited adjustable range, which cannot meet the scenarios where the power converter has a wide input voltage range and multiple working states. Also, the current software overcurrent protection method has the following problems: the overcurrent protection has a high delay and a long reaction time, and it cannot act quickly to perform overcurrent protection, which is not conducive to reducing the voltage stress of the power tube. Based on this, the embodiment of the present application provides a power converter with an overcurrent protection function, which can not only flexibly, dynamically and linearly adjust the overcurrent protection point after the power converter is powered on, but also is a hardware overcurrent protection method, which can achieve fast overcurrent protection, which is conducive to reducing the voltage stress of the power tube in the power converter.

[0046] FIG1 first illustrates a schematic diagram of a possible scenario applicable to an embodiment of the present application. Referring to FIG1 , this scenario includes photovoltaic modules, energy storage batteries, a power converter, and a power grid. The photovoltaic modules can convert solar energy into direct current (DC) through the photovoltaic effect, and the power converter can convert the DC into alternating current (AC) before feeding it into the power grid. Alternatively, the power converter can convert the DC from the energy storage battery into alternating current (AC) before feeding it into the power grid.

[0047] FIG2 is a schematic diagram of the structure of a power converter provided by an embodiment of the present application. As shown in FIG2, the power converter includes an inverter circuit 01, a filter circuit 02, a voltage regulator circuit 03, and a controller 04. Among them, the inverter circuit 01 is used to convert the direct current (DC) from the photovoltaic module or the energy storage battery into alternating current (AC), the filter circuit 02 is used to filter the ripple of the alternating current (AC) output by the inverter circuit 01, and the voltage regulator circuit 03 is used to output a first voltage V with a variable voltage value. IL-ref , that is, the first voltage V IL-ref Adjustable.

[0048] That is, the inverter circuit 01 included in the power converter has the function of converting direct current (DC) and alternating current (AC). For example, the inverter circuit 01 can convert direct current (DC) from a photovoltaic module or energy storage battery into alternating current (AC) and transmit the alternating current (AC) to a load, thereby providing power to the load. The load here can be, for example, the power grid shown in Figure 1. The filter circuit 02 can filter the alternating current (AC) converted by the inverter circuit 01 to remove ripple in the alternating current (AC) and ensure the stability and smoothness of the output alternating current (AC). Based on this, it can be seen that, as shown in Figure 2, the inverter circuit 01 can be connected to a photovoltaic module or energy storage battery, and can be connected to a load to convert direct current (DC) from the photovoltaic module or energy storage battery into alternating current (AC) and output it to the load. The filter circuit 02 can be connected between the inverter circuit 01 and the load, that is, the inverter circuit 01 can be indirectly connected to the load through the filter circuit 02 to filter the alternating current (AC) output by the inverter circuit 01 before outputting it to the load. As can be seen, "connected" in the embodiments of the present application can mean directly connected or indirectly connected.

[0049] It should also be understood that the present embodiment of the present application does not limit the circuit topology of the inverter circuit 01. Any circuit topology capable of converting direct current (DC) to alternating current (AC) is applicable to the present application, such as a voltage-type inverter circuit or a current-type inverter circuit. Furthermore, the filter circuit 02 in the present embodiment of the present application may include an inductor for filtering, namely, the power inductor described above.

[0050] Furthermore, in the embodiment of the present application, when the voltage on the DC side of the inverter circuit 01 is greater than or equal to the set voltage threshold, the controller 04 is configured to reduce the first voltage V IL-ref That is, the controller 04 can obtain the voltage on the DC side of the inverter circuit 01, and can reduce the first voltage V output by the voltage regulating circuit 03 when detecting that the voltage on the DC side of the inverter circuit 01 is large. IL-ref On this basis, as shown in FIG2 , the controller 04 can be connected to the DC side of the inverter circuit 01 and the voltage regulating circuit 03 respectively to obtain the voltage of the DC side of the inverter circuit 01 and control the voltage regulating circuit 03 to adjust the output first voltage V IL-ref FIG2 schematically shows only the DC side where the controller 04 is connected to the inverter circuit 01 and the energy storage battery.

[0051] And, when the first voltage V IL-ref Less than the second voltage V IL The controller 04 is used to reduce the alternating current AC flowing through the inductor in the filter circuit 02 or to issue an alarm signal. The second voltage V ILThe second voltage V is positively correlated with the current value IL of the alternating current AC flowing through the inductor in the filter circuit 02. That is, the controller 04 can also obtain the second voltage V that is positively correlated with the current value IL of the alternating current AC flowing through the inductor in the filter circuit 02. IL , and can detect the second voltage V IL Greater than the first voltage V IL-ref When the AC current flowing through the inductor of the filter circuit 02 is reduced or an alarm signal is issued. Based on this, as shown in FIG2 , the controller 04 can also be connected to the filter circuit 02 to obtain a second voltage V IL .

[0052] Among them, the second voltage V IL The positive correlation with the current value IL of the alternating current AC flowing through the inductor in the filter circuit 02 may mean that when the current value IL of the alternating current AC flowing through the inductor increases, the second voltage V IL The voltage value of the second voltage V IL As mentioned above, when the current value IL of the alternating current AC flowing through the inductor is large, it will cause abnormal overcurrent in the power converter. IL Greater than the first voltage V IL-ref When: In one implementation, the controller 04 can achieve overcurrent protection for the power converter by reducing the alternating current AC flowing through the inductor in the filter circuit 02. In another implementation, the controller 04 can alert the staff that the power converter has an abnormal overcurrent phenomenon at this time by issuing an alarm signal, so that the staff can perform overcurrent protection on the power converter. For example, the staff can use the controller 04 to reduce the alternating current AC flowing through the inductor in the filter circuit 02. In turn, it is possible to prevent large currents from damaging the components in the power converter, thereby achieving better overcurrent protection for the power converter. On this basis, it can be known that the first voltage V IL-ref This is the overcurrent protection point mentioned above. The first voltage V IL-ref It can also be called the reference voltage or threshold voltage of overcurrent protection. The first voltage V IL-ref Adjustable means the overcurrent protection point is adjustable. The second voltage V IL It may refer to the actual sampled voltage. Optionally, the alarm signal may be at least one of a text signal, a sound signal, and a photoelectric signal.

[0053] Optionally, the voltage on the DC side of the inverter circuit 01 may refer to the input voltage received by the DC side of the inverter circuit 01, such as the voltage of the direct current (DC) from a photovoltaic panel or an energy storage battery. The set voltage threshold may be a voltage threshold pre-set in the controller 04, and of course, it may also be flexibly adjusted. Furthermore, the voltage on the DC side of the inverter circuit 01 being greater than or equal to the set voltage threshold may mean that the input voltage received by the DC side of the inverter circuit 01 is relatively large. Because the greater the input voltage received by the inverter circuit 01, the greater the voltage peak of the power tube in the inverter circuit 01, and thus the greater the voltage stress of the power tube, that is, the power tube may be at risk of high voltage stress. Therefore, when the voltage on the DC side of the inverter circuit 01 is relatively large, the controller 04 can effectively reduce the inductor current peak by reducing the first voltage (i.e., reducing the overcurrent protection point), thereby effectively reducing the voltage stress of the power tube in the inverter circuit 01.

[0054] It can be understood that the above description is based on the premise that the voltage on the DC side of the inverter circuit 01 is greater than or equal to the set voltage threshold. In some embodiments, when the voltage on the DC side of the inverter circuit 01 is small, the controller 04 can also flexibly increase the first voltage. That is, in the embodiment of the present application, for the working condition of high input voltage, the controller 04 can lower the overcurrent protection point so that a smaller overcurrent protection point can trigger the overcurrent protection of the power converter, thereby achieving overcurrent protection while also reducing the voltage stress of the power tube in the inverter circuit 01. For the working condition of low input voltage, the controller 04 can flexibly increase the overcurrent protection point so that a larger overcurrent protection point can trigger the overcurrent protection of the power converter, thereby improving the flexibility of overcurrent protection. And, the above description is based on the first voltage V IL-ref Less than the second voltage V IL In some embodiments, when the first voltage V IL-ref Greater than the second voltage V IL , that is, the second voltage V IL Less than the first voltage V IL-ref , the controller 04 does not need to reduce the alternating current AC flowing through the inductor in the filter circuit 02 or issue an alarm signal, that is, it does not perform overcurrent protection on the power converter.

[0055] In summary, an embodiment of the present application provides a power converter. The power converter includes an inverter circuit, a filter circuit, a voltage regulator circuit, and a controller. The controller is capable of reducing the AC current flowing through the inductor in the filter circuit or issuing an alarm signal when the second voltage is greater than the first voltage, and is capable of reducing the first voltage output by the voltage regulator circuit when the voltage on the DC side of the inverter circuit is large. Because the second voltage is positively correlated with the current value of the AC current flowing through the inductor, overcurrent protection can be achieved for the power converter by reducing the AC current flowing through the inductor or issuing an alarm signal when the second voltage is greater than the first voltage, preventing high current from damaging components in the power converter. Furthermore, because the voltage stress on the power transistors in the inverter circuit increases with the voltage on the DC side of the inverter circuit, the voltage stress on the power transistors in the inverter circuit can be reduced by reducing the first voltage when the voltage on the DC side of the inverter circuit is large, that is, lowering the overcurrent protection point.

[0056] Optionally, in the embodiment of the present application, controller 04 can be used to reduce the duty cycle of the power transistors in inverter circuit 01 to reduce the alternating current (AC) flowing through the inductor in filter circuit 02, thereby providing overcurrent protection for the power converter. Based on this, it can be seen that controller 04 can also be connected to inverter circuit 01 to flexibly adjust the duty cycle of the power transistors in inverter circuit 01.

[0057] It is understood that a power transistor is a type of switching transistor. The duty cycle may refer to the duty cycle of a drive signal provided to the switching transistor, and the drive signal may be a pulse-width modulation (PWM) signal. That is, the duty cycle may refer to the duty cycle of the PWM signal received by the switching transistor. A PWM signal is a pulse signal having multiple switching cycles. Within each switching cycle, the PWM signal generally includes an active-level signal and an inactive-level signal. The active-level signal is used to control the switching transistor receiving the PWM signal to turn on (also called conduction), and the inactive-level signal is used to control the switching transistor receiving the PWM signal to turn off (also called cutoff). Furthermore, if the switching transistor is an N-type transistor, the active-level signal may be a high-level signal relative to the inactive-level signal. If the switching transistor is a P-type transistor, the active-level signal may be a low-level signal relative to the inactive-level signal. The duty cycle of a PWM signal may refer to the ratio of the duration of the active-level signal within a switching cycle to the total duration of the entire switching cycle.

[0058] It can be seen from this that the controller 04 can reduce the on-time of the power tube by reducing the duty cycle of the power tube in the inverter circuit 01, and thus reduce the current value IL of the alternating current AC output by the inverter circuit 01. In one scenario, when the controller 04 reduces the duty cycle of the power tube in the inverter circuit 01 to 0, the power tube can remain in the off state. At this time, it can be considered that the controller 04 controls the inverter circuit 01 to stop working. Of course, in some other embodiments, the controller 04 can also reduce the alternating current AC flowing through the inductor in the filter circuit 02 by lowering the amplitude of the PWM signal. Optionally, the controller 04 can be a microcontroller unit (MCU).

[0059] Alternatively, FIG3 is a schematic diagram of the structure of another power converter provided by an embodiment of the present application. As shown in FIG3, the power converter may further include a sampling circuit 05 and a comparison circuit 06. The sampling circuit 05 may be used to sample the alternating current AC flowing through the inductor in the filter circuit 02 and convert the alternating current AC into a second voltage V IL The output of the sampling circuit 05 can be connected to the negative input terminal - of the comparison circuit 06, the output of the voltage regulating circuit 03 can be connected to the positive input terminal + of the comparison circuit 06, and the output of the comparison circuit 06 can be connected to the controller 04. The comparison circuit 06 can also be called a comparator.

[0060] On this basis, it can be seen that the voltage at the negative input terminal - of the comparison circuit 06 is the second voltage V output by the sampling circuit 05. IL The voltage at the positive input terminal + of the comparison circuit 06 is the first voltage V output by the voltage regulation circuit 03. IL-ref The comparison circuit 06 can be based on the first voltage V IL-ref and the second voltage V IL The voltage value of the output is output to the controller 04. IL-OCP , to indicate whether the controller 04 is performing overcurrent protection on the power converter. That is, as shown in FIG3 , the controller 04 can be indirectly connected to the voltage regulating circuit 03 via the comparison circuit 06 , and the controller 04 can be indirectly connected to the filter circuit 02 via the comparison circuit 06 and the sampling circuit 05 .

[0061] Based on the working principle of comparison circuit 06, "when the comparison determines that the voltage of the positive input terminal + is greater than the voltage of the negative input terminal -, a high-level signal is output to the output terminal; when the comparison determines that the voltage of the positive input terminal + is less than the voltage of the negative input terminal -, a low-level signal is output to the output terminal", it can be known that:

[0062] When the second voltage V IL Less than the first voltage V IL-ref, that is, the voltage of the negative input terminal - of the comparison circuit 06 is less than the voltage of the positive input terminal +, the comparison circuit 06 can output a high level overcurrent protection indication voltage V to the controller 04 IL-OCP At this time, the controller 04 can determine the second voltage V IL Small, that is, it can be determined that the current value IL of the alternating current AC flowing through the inductor in the filter circuit 02 is small, and the power converter does not have an abnormal overcurrent phenomenon at this time, and the power converter is not subjected to overcurrent protection.

[0063] When the second voltage V IL Greater than the first voltage V IL-ref , that is, the voltage of the negative input terminal - of the comparison circuit 06 is greater than the voltage of the positive input terminal +, the comparison circuit 06 can output a low-level overcurrent protection indication voltage V to the controller 04 IL-OCP At this time, the controller 04 can determine the second voltage V IL It is larger, that is, it can be determined that the current value IL of the alternating current AC flowing through the inductor in the filter circuit 02 is larger, and the power converter has an abnormal overcurrent phenomenon at this time, so the power converter is protected from overcurrent.

[0064] It is understandable that the low level and high level here are relative. For example, assuming binary representation, the low level overcurrent protection indication voltage V IL-OCP It can be marked as 0, the high level overcurrent protection indication voltage V IL-OCP It can be marked as 1.

[0065] It can also be understood that by setting the comparison circuit 06 to compare the second voltage V IL and the first voltage V IL-ref , the second voltage V can be accurately and quickly determined IL and the first voltage V IL-ref The size of , thereby enabling the controller 04 to quickly determine whether an abnormal overcurrent phenomenon currently occurs in the power converter, and to promptly perform overcurrent protection on the power converter when an overcurrent phenomenon is determined to occur, with a better overcurrent protection effect.

[0066] Optionally, the sampling circuit 05 described in the embodiment of the present application may include: a sampling resistor. It is understandable that by using the sampling resistor as the sampling circuit 05, the alternating current AC flowing through the inductor in the filter circuit 02 can be reliably sampled, and the current value IL of the alternating current AC can be converted into the second voltage V IL Then it is output to the comparison circuit 06, so that the comparison circuit 06 can reliably output the overcurrent protection indication voltage V to the controller 04. IL-OCP , to instruct the controller 04 to provide better overcurrent protection for the power converter.

[0067] Optionally, FIG4 is a schematic structural diagram of another power converter provided in an embodiment of the present application. As shown in FIG4 , the power converter may further include a direct current (DC) to direct current (DC) conversion circuit 07. The DC / DC conversion circuit 07 may be used to change the voltage of the direct current (DC) from the photovoltaic module or the energy storage battery, and may output the transformed direct current (DC) to the inverter circuit 01. On this basis, it can be seen that, as shown in FIG4 , the DC / DC conversion circuit 07 may be connected between the photovoltaic module and the inverter circuit 01, or between the energy storage battery and the inverter circuit 01, so as to perform DC / DC conversion on the voltage of the direct current (DC) from the photovoltaic module or the energy storage battery and then output it to the inverter circuit 01. That is, the inverter circuit 01 may be indirectly connected to the photovoltaic module or the energy storage battery via the DC / DC conversion circuit 07.

[0068] Optionally, based on the power converter including the DC / DC conversion circuit 07, the voltage on the DC side of the inverter circuit described above may include the voltage at the input of the DC / DC conversion circuit, that is, the voltage of the direct current (DC) provided by the photovoltaic module or energy storage battery. Alternatively, in some other embodiments, the voltage on the DC side of the inverter circuit may also be the voltage of the direct current (DC) output by the DC / DC conversion circuit 07 to the inverter circuit 01, that is, the voltage after the DC / DC conversion circuit 07 converts the voltage of the direct current (DC) from the photovoltaic module or energy storage battery.

[0069] Optionally, FIG5 is a schematic diagram of the structure of another power converter provided by an embodiment of the present application. As shown in FIG5 , the power converter may further include a signal processing circuit 08. The signal processing circuit 08 may be used to process the second voltage V IL Perform at least one of amplification, filtering and voltage stabilization, and convert the processed second voltage V IL Output to the controller 04. Accordingly, it can be known that the signal processing circuit 08 may include at least one of the following circuits: an amplifier for amplification processing, a filter circuit for filtering processing, and a voltage stabilization circuit for voltage stabilization processing.

[0070] It can be understood that, based on the indirect connection between the controller 04 and the filter circuit 02 via the sampling circuit 05 and the comparison circuit 06, as shown in FIG5 , the signal processing circuit 08 can be a circuit that processes the processed second voltage V IL Output to the comparison circuit 06. And, based on this, it can be known that, as shown in FIG5 , the signal processing circuit 08 can be connected between the sampling circuit 05 and the negative input terminal - of the comparison circuit 06 to convert the second voltage V output by the sampling circuit 05 into IL After the above processing, it is output to the negative input terminal - of the comparison circuit 06.

[0071] It can also be understood that by setting the signal processing circuit 08 to process the second voltage V IL After amplification, filtering and / or voltage stabilization, the output is output to the comparison circuit 06, which can ensure that the output second voltage V IL The reliability is good. Furthermore, the comparison circuit 06 can accurately compare the second voltage V IL and the first voltage V IL-ref The size of the overcurrent protection indication voltage V is output to the controller 04 IL-OCP , to instruct the controller 04 to provide better overcurrent protection for the power converter.

[0072] Optionally, in the embodiment of the present application, the signal processing circuit 08 and the sampling circuit 05 can be integrated. Accordingly, in the embodiment of the present application, the circuit including the signal processing circuit 08 and the sampling circuit 05 can also be called a sampling conditioning circuit.

[0073] Alternatively, FIG6 is a schematic diagram of the circuit structure of a voltage regulating circuit provided in an embodiment of the present application. As shown in FIG6 , the voltage regulating circuit 03 may include a switch tube Q, a first resistor R1, a second resistor R2, and a capacitor C. The collector of the switch tube Q may be connected to the power supply terminal VCC through the first resistor R1 and the second resistor R2 connected in series, the emitter of the switch tube Q may be grounded (i.e., connected to the ground terminal GND), the capacitor C may be connected in parallel between the series connection point of the first resistor R1 and the second resistor R2 and the emitter of the switch tube Q, the series connection point of the first resistor R1 and the second resistor R2 and the base of the switch tube Q may be connected to the controller 04. It can be understood that, based on FIG5 , the series connection point of the first resistor R1 and the second resistor R2 may be connected to the non-inverting input terminal + of the comparison circuit 06 to be indirectly connected to the controller 04. And, the base of the switch tube Q may be connected to the output terminal of the controller 04 to receive the duty cycle provided by the controller 04.

[0074] Among them, the first voltage V IL-ref is negatively correlated with the duty cycle of the switch tube Q. That is, when the duty cycle of the switch tube Q increases, the first voltage V IL-ref The voltage value of the switch tube Q decreases accordingly; when the duty cycle of the switch tube Q decreases, the first voltage V IL-ref On this basis, in the embodiment of the present application, when the voltage on the DC side of the inverter circuit 01 is greater than or equal to the set voltage threshold, the controller 04 can be used to increase the duty cycle of the switch tube Q to reduce the first voltage V IL-ref , that is, lowering the overcurrent protection point. And, when the voltage on the DC side of the inverter circuit 01 decreases, the controller 04 can also be used to reduce the duty cycle of the switch tube Q to increase the first voltage V IL-ref , that is, increase the overcurrent protection point.

[0075] Optionally, as mentioned above, the duty cycle of the switch tube Q may refer to the duty cycle of the PWM signal received by the switch tube Q. That is, in the embodiment of the present application, the controller 04 may adjust the duty cycle of the PWM signal provided to the switch tube Q to adjust the first voltage V output by the voltage regulation circuit 03. IL-ref Since the duty cycle of the PWM signal can be adjusted linearly, the first voltage V IL-ref It can also be adjusted in real time, dynamically, and linearly, with a wide adjustable range and a wide range of application scenarios.

[0076] Optionally, the voltage of the power signal provided by the power supply terminal VCC may be 3 volts (V). The voltage of the power signal provided by the ground terminal GND may be 0. Of course, this is merely an illustrative example. For example, in some other embodiments, the ground terminal GND may be replaced by another power terminal, such as the ground terminal GND may be replaced by a power terminal VSS that provides a power signal with a voltage of -3V.

[0077] Optionally, as described above, the switch tube Q can be an N-type transistor or a P-type transistor. For an N-type transistor, if the gate receives a high-level signal, it is turned on, and if the gate receives a low-level signal, it is turned off; for a P-type transistor, if the gate receives a low-level signal, it is turned on, and if the gate receives a high-level signal, it is turned off. The embodiment of the present application takes the switch tube Q as an N-type transistor as an example. On this basis, combined with Figure 6, the voltage regulating circuit 03 adjusts the first voltage V IL-ref The principle is explained as follows:

[0078] For example, based on Figure 6, Figure 7 shows a schematic diagram of the duty cycle of switch Q in voltage regulation circuit 03 (i.e., the PWM signal received by switch Q). The horizontal axis represents time t, and the vertical axis represents the level of the PWM signal. Furthermore, in conjunction with Figures 6 and 7, Figure 8 shows a schematic diagram of operating mode 1 of voltage regulation circuit 03 when switch Q is on, and Figure 9 shows a schematic diagram of operating mode 2 of voltage regulation circuit 03 when switch Q is off (indicated by a dashed line × in the figure). Figures 8 and 9 also illustrate the current flow in different operating modes.

[0079] Based on FIG6 to FIG9, it is assumed that the switching period of the PWM signal is T, the duty cycle is D, and the resistance value of the first resistor R1 is R R1 , the resistance value of the second resistor R2 is R R2 , the voltage across the capacitor C is Vc, and the voltage of the power signal provided by the first power supply terminal VCC is V VCC . Then we can determine:

[0080] Referring to Figures 7 and 8, in working mode 1, when t = [0, DT], the switch tube Q can be turned on, and the capacitor C can be discharged to the ground through the second resistor R2, that is, Vc can be in a decreasing state. In addition, the discharge current i1 can satisfy: i1 = Vc / R R2 -(V VCC -Vc) / R R1 .

[0081] Referring to FIG7 and FIG9, in working mode 2, when t=[DT, T], the switch tube Q can be turned off, and the capacitor C can be charged through the first resistor R1, that is, Vc can be in a rising state. Moreover, the charging current i2 can satisfy: i2=(V VCC -Vc) / R R1 .

[0082] It is understandable that when the voltage regulating circuit 03 is in steady state, the voltage across the capacitor C can remain stable within the switching period T. That is, the amount of electricity when charging the capacitor C should be equal to the amount of electricity when discharging the capacitor C. Therefore, according to the formula for calculating the amount of electricity Q, Q = i*t (current*time), the first voltage V can be determined. IL-ref Satisfy the following formula (1): V IL-ref =Vc=R R2 / (D*R R1 +R R2 )*V VCC Formula (1);

[0083] According to formula (1), the duty cycle D can change the first voltage V of the overcurrent protection IL-ref , to achieve dynamic adjustment of the overcurrent protection point. And, in the extreme case, when D=0, V IL-ref =V VCC ; When D = 1, V IL-ref =R R2 / (R R1 +R R2 )*V VCC .

[0084] That is, in the voltage regulation circuit 03, the switch tube Q can be turned on or off based on the received PWM signal. Moreover, when the switch tube Q is turned on, the capacitor C can be discharged; when the switch tube Q is turned off, the capacitor C can be discharged. Based on the charging and discharging of the capacitor C, a first voltage V can be output that is negatively correlated with the duty cycle of the PWM signal. IL-ref , to adjust the first voltage V IL-ref purpose.

[0085] Optionally, the controller 04 may be configured to increase the duty cycle of the switch Q from a first duty cycle to a second duty cycle, and then decrease the duty cycle from the second duty cycle to a third duty cycle, wherein the third duty cycle may be greater than the first duty cycle. That is, when increasing the first duty cycle to the third duty cycle, the controller 04 may first increase the duty cycle to a second duty cycle that is greater than the third duty cycle, and then decrease the duty cycle to the third duty cycle.

[0086] It can be understood that, in conjunction with Figures 6 and 7, the greater the duty cycle of the switch tube Q, the higher the efficiency of discharging the capacitor C in the voltage regulation circuit 03; conversely, the smaller the duty cycle of the switch tube Q, the higher the efficiency of charging the capacitor C in the voltage regulation circuit 03. Therefore, by increasing the duty cycle of the switch tube Q from the first duty cycle to a second duty cycle that is greater than the third duty cycle before increasing the duty cycle from the first duty cycle to the third duty cycle, the efficiency of discharging the capacitor C in the voltage regulation circuit 03 can be improved, thereby improving the voltage regulation circuit 03's ability to reduce the first voltage V IL-ref The efficiency is improved, so that the controller 04 can perform overcurrent protection on the power converter faster, and the overcurrent protection effect is better.

[0087] Optionally, assuming that the first duty cycle is 25% and the third duty cycle is 50%, the second duty cycle can be 100%. It can be understood that, based on setting the second duty cycle to 100%, the switch tube Q in the voltage regulation circuit 03 can be kept in the on state, thereby quickly discharging the capacitor C, thereby achieving rapid regulation of the first voltage V IL-ref purpose.

[0088] It is understandable that, in the scenario where the first duty cycle is greater than the third duty cycle, that is, the controller 04 reduces the duty cycle of the switch tube Q, the controller 04 can first reduce the first duty cycle to a fourth duty cycle that is smaller than the third duty cycle, and then increase the fourth duty cycle to the third duty cycle. In this way, the efficiency of charging the capacitor C in the voltage regulating circuit 03 can be improved, thereby improving the voltage regulating circuit 03 to increase the first voltage V IL-ref efficiency.

[0089] For example, in conjunction with FIG6 , when the power converter is operating normally, the current overcurrent protection point is 20 amperes (A), and when the voltage on the DC side of the inverter circuit 01 is greater than 700V, the initial overcurrent protection point needs to be reduced from 20A to 10A. The working principle of the power converter is described as follows:

[0090] Assume that the current value IL of the alternating current AC flowing through the inductor of the filter circuit 02 is in the range of [-10A, 50A]. After the sampling and conditioning circuit, the first voltage V output to the negative input terminal of the comparison circuit 06 is IL-ref The range is [0, 3V]. The voltage V of the power signal provided by the power supply terminal VCCVCC The resistance value of the first resistor R1 is R R1 R R1 =4 kilo-ohms (kΩ). The resistance value of the second resistor R2 is R R2 R R2 =1kΩ. The capacitance value of capacitor C is Cc = 1 microfarad (μF).

[0091] When the overcurrent protection point is 20A, the controller 04 can first determine the corresponding first voltage V IL-ref It is 1.5V. Therefore, the voltage regulating circuit 03 adjusts the first voltage V IL-ref Adjusted to 1.5V, the controller 04 can trigger the overcurrent protection when the current value IL of the alternating current AC flowing through the inductor is greater than 20A. In this way, the controller 04 substitutes the above parameters into the above formula (1) and can calculate that the duty cycle D is 25%. That is, at this time, the controller 04 can provide a PWM signal with a duty cycle of 25% to the switch tube Q in the voltage regulation circuit 03, so that the voltage regulation circuit 03 outputs a first voltage V of 1.5V to the positive input terminal + of the comparison circuit 06. IL-ref , the first voltage V of 1.5V IL-ref The indicated overcurrent protection point is 20A. On this basis, when the current value IL of the alternating current AC flowing through the inductor is less than 20A, the sampling and conditioning circuit outputs the second voltage V to the negative input terminal - of the comparison circuit 06. IL is less than the first voltage V IL-ref , that is, V IL-ref >V IL Furthermore, the comparison circuit 06 can determine that the voltage of the positive phase input terminal + is greater than the voltage of the negative phase input terminal -, and output a high level overcurrent protection indication voltage V to the controller 04. IL-OCP The controller 04 checks the high level overcurrent protection indication voltage V IL-OCP When the current value IL of the alternating current AC flowing through the inductor is greater than 20A, the sampling and conditioning circuit outputs the second voltage V to the negative input terminal - of the comparison circuit 06. IL is greater than the first voltage V IL-ref , that is, V IL-ref <V IL Furthermore, the comparison circuit 06 can determine that the voltage of the positive phase input terminal + is less than the voltage of the negative phase input terminal -, and output a low level overcurrent protection indication voltage V to the controller 04. IL-OCP The controller 04 checks the low level overcurrent protection indication voltage V IL-OCP When the power converter is overcurrent, it can be determined that the power converter has an overcurrent phenomenon and the power converter is protected from overcurrent.

[0092] When the voltage on the DC side of the inverter circuit 01 is greater than 700V, the overcurrent protection point 20A needs to be reduced to 10A. At this time, the controller 04 can also first determine the second voltage V corresponding to the current value IL of the alternating current AC flowing through the inductor is 10A. IL It is 1V. Therefore, it can be seen that the voltage regulating circuit 03 adjusts the first voltage V IL-ref By adjusting the voltage from 1.5V to 1V, the controller 04 can trigger the overcurrent protection when the current value IL of the alternating current AC flowing through the inductor is greater than 10A. Thus, the controller 04 substitutes the above parameters into the above formula (1) and calculates that the duty cycle D is 50%. In other words, at this time, the controller 04 can increase the duty cycle of the PWM signal provided to the switch tube Q in the voltage regulation circuit 03 from 25% to 50%, so that the voltage regulation circuit 03 lowers the overcurrent protection point from 20A to 10A, thereby enabling the comparison circuit 06 to trigger the controller 04 to perform overcurrent protection on the power converter when the current value IL of the alternating current AC flowing through the inductor is greater than 10A.

[0093] Furthermore, for example, the controller 04 adjusts the duty cycle of the switch tube Q in the voltage regulating circuit 03 from 25% (the first duty cycle) to 50% (the third duty cycle), so that the first voltage V IL-ref Taking the adjustment from 1.5V to 1V as an example, the duty cycle adjustment process is introduced:

[0094] In one embodiment, as shown in FIG10 , the controller 04 can directly increase the duty cycle from 25% to 50%. However, since the capacitor C needs a certain amount of time to charge and discharge, the first voltage V IL-ref Only then can it slowly drop from 1.5V to 1V, which is not conducive to improving dynamic performance.

[0095] In another embodiment, as shown in FIG11 , the controller 04 may first increase the duty cycle from 25% to a larger second duty cycle of 100%, so that the switch Q in the voltage regulating circuit 03 remains on. Afterwards, several switching cycles are continued until the first voltage V IL-ref After the first voltage V is rapidly reduced from 1.5V to 1V, the controller 04 can further reduce the duty cycle from 100% to 50%, thereby making the first voltage V IL-ref Stable at 1V. In this way, the first voltage V can be quickly adjusted. IL-ref The purpose is to improve the dynamic performance.

[0096] Optionally, in some embodiments, the controller 04 may also be configured to reduce the duty cycle of the switch Q in the voltage regulating circuit 03 when the current value IL of the alternating current AC flowing through the inductor in the filter circuit 02 increases or the ripple increases, so as to increase the first voltage V IL-ref, that is, increase the overcurrent protection point so that the overcurrent protection is triggered only when the overcurrent protection point is larger; on the contrary, when the current value IL of the alternating current AC flowing through the inductor in the filter circuit 02 is reduced or the ripple is reduced, increase the duty cycle of the switch tube Q in the voltage regulation circuit 03 to reduce the first voltage V IL-ref , that is, lowering the overcurrent protection point so that the smaller overcurrent protection point triggers overcurrent protection. This allows for better adaptation to overcurrent protection in different scenarios. Specifically, if the AC flowing through the inductor in filter circuit 02 is already high, controller 04 can trigger overcurrent protection only when the AC flowing through the inductor exceeds the larger overcurrent protection point. Alternatively, if the AC flowing through the inductor in filter circuit 02 is already low, controller 04 can trigger overcurrent protection only when the AC flowing through the inductor exceeds the smaller overcurrent protection point. This ensures the reliability of overcurrent protection and avoids false protection.

[0097] It can be understood that since the alternating current AC flowing through the inductor in the filter circuit 02 is generally determined based on the input voltage, operating power and output voltage of the inverter circuit 01, in the embodiment of the present application, the controller 04 can also be used to obtain the input voltage, operating power and output voltage of the inverter circuit 01, and calculate the current value IL and ripple size of the alternating current AC flowing through the inductor in the filter circuit 02 based on the obtained input voltage, operating power and output voltage.

[0098] It is also understood that the solutions provided in the embodiments of the present application are not limited to dynamic overcurrent protection scenarios in which the overcurrent protection point is dynamically adjusted. For example, in some embodiments, the solutions can also be applied to protection scenarios such as dynamic overtemperature protection, dynamic overvoltage protection, and other safety protection scenarios, where other safety protections can include, for example, safety protection under arc detection or safety protection under insulation (ISO) impedance detection.

[0099] For example, for dynamic overtemperature protection, sampling circuit 05 can be a thermistor capable of sampling temperature. For safety protection under arc detection, sampling circuit 05 can be an arc-fault circuit-interrupter (AFCI) capable of detecting arcs. For safety protection under insulation resistance detection, sampling circuit 05 can be an ISO detection circuit capable of detecting insulation resistance.

[0100] In summary, an embodiment of the present application provides a power converter. The power converter includes an inverter circuit, a filter circuit, a voltage regulator circuit, and a controller. The controller is capable of reducing the AC current flowing through the inductor in the filter circuit or issuing an alarm signal when the second voltage is greater than the first voltage, and is capable of reducing the first voltage output by the voltage regulator circuit when the voltage on the DC side of the inverter circuit is large. Because the second voltage is positively correlated with the current value of the AC current flowing through the inductor, overcurrent protection can be achieved for the power converter by reducing the AC current flowing through the inductor or issuing an alarm signal when the second voltage is greater than the first voltage, preventing high current from damaging components in the power converter. Furthermore, because the voltage stress on the power transistors in the inverter circuit increases with the voltage on the DC side of the inverter circuit, the voltage stress on the power transistors in the inverter circuit can be reduced by reducing the first voltage when the voltage on the DC side of the inverter circuit is large, that is, lowering the overcurrent protection point.

[0101] The present application also provides a method for overcurrent protection of a power converter. As shown in FIG12 , the method includes:

[0102] Step 1201: When the voltage on the DC side of the inverter circuit in the power converter is greater than or equal to a set voltage threshold, reduce the first voltage.

[0103] The first voltage is the voltage output by the voltage regulating circuit in the power converter. As shown in Figure 2, the inverter circuit 01 can be used to convert direct current from a photovoltaic module or an energy storage battery into alternating current, that is, the inverter circuit 01 can be connected to a photovoltaic module or an energy storage battery. Accordingly, it can be seen that the voltage on the DC side of the inverter circuit can include, for example, the voltage of the direct current from the photovoltaic module or the energy storage battery. As previously described, in an embodiment of the present application, the controller 04 can reduce the first voltage output by the voltage regulating circuit when it detects that the voltage on the DC side of the inverter circuit is large, thereby reducing the voltage stress of the power tube in the inverter circuit 01.

[0104] Step 1202: When the first voltage is lower than the second voltage, reduce the AC current flowing through the inductor included in the filter circuit in the power converter or issue an alarm signal.

[0105] Among them, the second voltage is positively correlated with the current value of the alternating current flowing through the inductor in the filter circuit. That is, when the current value of the alternating current flowing through the inductor in the filter circuit increases, the second voltage also increases accordingly; when the current value of the alternating current flowing through the inductor in the filter circuit decreases, the second voltage also decreases accordingly. The second voltage may refer to a sampling circuit. As shown in Figure 2, the filter circuit 02 may be connected to the inverter circuit 01 and used to filter the ripple of the alternating current output by the inverter circuit 01. Accordingly, it can be seen that the alternating current flowing through the inductor in the filter circuit may refer to the alternating current output by the inverter circuit 01. As previously described, in an embodiment of the present application, the controller 04 can reduce the alternating current flowing through the inductor included in the filter circuit in the power converter or issue an alarm signal when detecting that the second voltage is greater than the first voltage, so as to achieve overcurrent protection for the power converter.

[0106] It can be understood that since the overcurrent protection method of the power converter has basically the same implementation method and technical effects as the power converter described in the above embodiments, for the purpose of brevity, the implementation method and technical effects of the overcurrent protection method will not be repeated here.

[0107] The present application also provides an energy storage system. As shown in FIG1 , the energy storage system includes an energy storage battery and a power converter as shown in any one of FIG2 to FIG5 . The energy storage battery is configured to provide direct current (DC) power to the power converter, which is configured to convert the DC power into alternating current (AC) power and output the converted AC power to a load to power the load.

[0108] The above are merely optional embodiments of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and such modifications or substitutions should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A power converter, characterized in that: The power converter includes an inverter circuit, a filter circuit, a voltage regulator circuit, and a controller, wherein the inverter circuit is used to convert direct current from a photovoltaic module or an energy storage battery into alternating current, the filter circuit is used to filter the ripple of the alternating current output by the inverter circuit, and the voltage regulator circuit is used to output a first voltage with a variable voltage value; When the voltage on the DC side of the inverter circuit is greater than or equal to a set voltage threshold, the controller is configured to reduce the first voltage; When the first voltage is less than a second voltage, the controller is used to reduce the AC current flowing through the inductor in the filter circuit or issue an alarm signal, and the second voltage is positively correlated with the current value of the AC current flowing through the inductor in the filter circuit.

2. The power converter according to claim 1, wherein: The voltage regulation circuit includes a switching tube, a first resistor, a second resistor and a capacitor. The collector of the switching tube is connected to the power supply end through the first resistor and the second resistor connected in series. The emitter of the switching tube is grounded. The capacitor is connected in parallel between the series connection point of the first resistor and the second resistor and the emitter of the switching tube. The series connection point of the first resistor and the second resistor and the base of the switching tube are connected to the controller. The first voltage is negatively correlated with the duty cycle of the switching tube.

3. The power converter according to claim 2, wherein: When the voltage on the DC side of the inverter circuit is greater than or equal to a set voltage threshold, the controller is configured to increase the duty cycle of the switch tube to reduce the first voltage.

4. The power converter according to claim 3, wherein: The controller is used to increase the duty cycle of the switch tube from a first duty cycle to a second duty cycle, and then reduce the second duty cycle to a third duty cycle, and the third duty cycle is greater than the first duty cycle.

5. The power converter according to any one of claims 1 to 4, characterized in that: The power converter also includes a sampling circuit and a comparison circuit. The sampling circuit is used to sample the alternating current flowing through the inductor in the filter circuit and convert the alternating current into the second voltage. The output end of the sampling circuit is connected to the negative phase input end of the comparison circuit, the output end of the voltage regulation circuit is connected to the positive phase input end of the comparison circuit, and the output end of the comparison circuit is connected to the controller.

6. The power converter according to any one of claims 1 to 5, characterized in that: The power converter also includes a DC / DC conversion circuit, which is used to change the voltage of the DC power from the photovoltaic module or the energy storage battery and output the transformed DC power to the inverter circuit. The voltage on the DC side of the inverter circuit includes the voltage at the input end of the DC / DC conversion circuit.

7. The power converter according to any one of claims 1 to 6, characterized in that: The controller is used to reduce the duty cycle of the power tube in the inverter circuit to reduce the alternating current flowing through the inductor in the filter circuit.

8. The power converter according to any one of claims 1 to 7, characterized in that: The power converter further includes a signal processing circuit configured to perform at least one of amplification, filtering, and voltage stabilization on the second voltage, and output the processed second voltage to the controller.

9. A method for overcurrent protection of a power converter, characterized in that: The method comprises: When the voltage on the DC side of the inverter circuit in the power converter is greater than or equal to a set voltage threshold, reducing a first voltage, where the first voltage is a voltage output by a voltage regulating circuit in the power converter, wherein the inverter circuit is used to convert DC power from a photovoltaic module or an energy storage battery into AC power; When the first voltage is less than the second voltage, the alternating current flowing through the inductor included in the filter circuit in the power converter is reduced or an alarm signal is issued. The second voltage is positively correlated with the current value of the alternating current flowing through the inductor in the filter circuit. The filter circuit is connected to the inverter circuit and is used to filter the ripple of the alternating current output by the inverter circuit.

10. An energy storage system, characterized in that: The energy storage system includes an energy storage battery and a power converter according to any one of claims 1 to 8, wherein the energy storage battery is used to provide direct current to the power converter, and the power converter is used to convert the direct current into alternating current and output the converted alternating current to a load to power the load.

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