Power converter and output current reconstruction method thereof

Abstract

The invention provides a power converter and an output current reconstruction method thereof, a high-speed current sensor is used for sampling and monitoring resonant current, a sampling circuit does not need to be additionally arranged on an alternating current output side, and the output current of the power converter is reconstructed by using the resonant current sampled by the current sensor and combining the working state of a switching tube in a secondary circuit. Therefore, the output current of the power converter can be reconstructed, the cost can be reduced, and the product competitiveness can be enhanced. Specifically, a first switching circuit and a second switching circuit are arranged between a sampling circuit and an operational circuit, and the working states of the first switching circuit and the second switching circuit depend on the on-off states of switching tubes in an upper bridge arm and a lower bridge arm of a secondary circuit. The output voltage of the operational circuit can accord with the characteristics of the actual output current of the bridge arm of the secondary circuit at the conduction time and the dead time, and the accuracy of reconstructing the output current can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a power converter and an output current reconstruction method thereof. Background Art

[0002] At present, with the global shortage of non-renewable energy and the worsening of environmental pollution, the application of photovoltaic power generation is becoming more and more widespread. Photovoltaic power generation is to convert the direct current generated by photovoltaic modules into alternating current through an inverter, and then connect it to the AC grid or provide it to the load. Micro inverters are one of the best inverter solutions for household photovoltaic power generation. Compared with string inverters, micro inverters have the following additional advantages in the field of household photovoltaics: (1) high power generation. Compared with component-level inverters, they can improve the maximum power point tracking (MPPT) efficiency; (2) high safety. Micro inverters use low-voltage parallel connection to minimize the risk of DC high voltage; (3) high reliability. The maintenance warranty period of micro inverters is generally 2-3 times that of string inverters, and the installation process of micro inverters can be modularized to simplify subsequent operation and maintenance.

[0003] For inverters, especially single-stage micro inverters, sampling or observation of grid-connected current is very important. By sampling the grid-connected current, the control accuracy of the micro inverter can be improved, system safety can be guaranteed, and system performance can be optimized. Therefore, grid-connected current sampling is an indispensable part of the inverter control system.

[0004] At present, the grid-connected current is generally obtained by adding a current sensor on the output side of the inverter and directly sampling the output current of the inverter using the current sensor. This requires additional hardware resources such as current sensors on the output side, which increases the sampling cost. Therefore, how to reconstruct the grid-connected current of the inverter with low hardware cost is a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] The present application provides a power converter and an output current reconstruction method thereof, which are used to achieve grid-connected current reconstruction with low hardware cost.

[0006] In the first aspect, the present application provides a power converter, including: a transformer, a primary circuit, a secondary circuit, a sampling circuit, a first switching circuit, a second switching circuit, an operation circuit and a filtering circuit. The input of the power converter is used to connect to a DC power supply, and the output of the power converter is used to connect to an AC power grid. The primary circuit is connected between the input of the power converter and the transformer, and the secondary circuit is connected between the transformer and the output of the power converter. The secondary circuit includes a bridge arm, a first capacitor and a second capacitor, the bridge arm includes an upper bridge arm and a lower bridge arm, the upper bridge arm includes two switch tubes with opposite freewheeling directions, the lower bridge arm includes two switch tubes with opposite freewheeling directions, the connection point of the upper half bridge arm and the lower half bridge arm is connected to one end of the secondary winding of the transformer, the first capacitor and the second capacitor are connected in series and then connected in parallel with the bridge arm, and the connection point of the first capacitor and the second capacitor is connected to the other end of the secondary winding of the transformer. The sampling circuit is located between the transformer and the secondary circuit, or the sampling circuit is located between the transformer and the primary circuit, and the sampling circuit is used to collect the resonant current of the transformer and output the sampling voltage. The first switch circuit is connected between the output of the sampling circuit and the first input of the operation circuit. The first switch circuit is used to output the sampling voltage to the operation circuit when both switch tubes of the upper bridge arm are turned on, and output the reference voltage to the operation circuit when any switch tube of the upper bridge arm is turned off. The reference voltage is a fixed value. The second switch circuit is connected between the output of the sampling circuit and the second input of the operation circuit. The second switch circuit is used to output the sampling voltage to the operation circuit when both switch tubes of the lower bridge arm are turned on, and output the reference voltage to the operation circuit when any switch tube of the lower bridge arm is turned off. The operation circuit is used to output the voltage difference between the first input and the second input receiving voltage of the operation circuit. The filter circuit is connected to the operation circuit, and the filter circuit is used to filter the voltage difference and filter out the high-frequency signal. The output voltage of the filter circuit can reconstruct the output current after passing through the EMI filter of the power converter.

[0007] Since the resonant current output by the transformer flows directly through the switch tube of the secondary circuit, in order to avoid the problem of current overcurrent, a high-speed current sensor is currently set between the transformer and the secondary circuit to sample and monitor the resonant current. In this application, there is no need to add an additional sampling circuit on the output side. The resonant current sampled by the current sensor, i.e., the sampling circuit, and the working state of the switch tube in the secondary circuit can be used to reconstruct the output current of the power converter, which can reduce the number of hardware components, reduce costs, and enhance product competitiveness.

[0008] Specifically, when determining the relationship between the output current and the resonant current, the different states of the bridge arm of the secondary circuit in the conduction time and the dead time are integrated, and the working states of the first switch circuit and the second switch circuit set between the sampling circuit and the operation circuit in the present application can be configured, so that the working states of the first switch circuit and the second switch circuit depend on the on-off states of the switch tubes in the upper bridge arm and the lower bridge arm of the secondary circuit. Specifically, when the two switch tubes of the upper bridge arm of the secondary bridge arm are both turned on, the first input of the operation circuit receives the sampling voltage, and the second input of the operation circuit receives the reference voltage. The reference voltage can be set to zero voltage, for example, and the operation circuit outputs the difference between the two, so that the reconstructed grid-connected current at this time meets the above relationship. When the two switch tubes of the lower bridge arm of the secondary bridge arm are both turned on, the second input of the operation circuit receives the sampling voltage, and the first input of the operation circuit receives the reference voltage. The operation circuit outputs the difference between the two, so that the reconstructed grid-connected current at this time meets the above relationship. When a switch tube in both the upper bridge arm and the lower bridge arm of the secondary bridge arm is turned on, the first input of the operation circuit receives the reference voltage, the second input of the operation circuit receives the reference voltage, and the operation circuit outputs the difference between the two, that is, zero voltage, so that the reconstructed grid-connected current at this time meets the above relationship. In summary, by configuring the working states of the first switch circuit and the second switch circuit, the output voltage of the operation circuit can meet the characteristics of the actual output current of the bridge arm of the secondary circuit during the conduction time and the dead time, and the accuracy of the reconstructed output current can be improved.

[0009] In some embodiments of the present application, the first switch circuit includes: a first switch tube connected in series between the output of the sampling circuit and the first input of the operation circuit, and a resistor connected in series between the reference voltage output terminal and the first input of the operation circuit, and the reference voltage output terminal is used to output the reference voltage; when both switch tubes of the upper bridge arm are turned on, the first switch tube is turned on, and when any switch tube of the upper bridge arm is turned off, the first switch tube is turned off. The second switch circuit includes: a second switch tube connected in series between the output of the sampling circuit and the second input of the operation circuit, and a resistor connected in series between the reference voltage output terminal and the second input of the operation circuit; when both switch tubes of the lower bridge arm are turned on, the second switch tube is turned on, and when any switch tube of the lower bridge arm is turned off, the second switch tube is turned off.

[0010] In some other embodiments of the present application, the first switch circuit includes: a first switch tube and a resistor connected in parallel between the output of the sampling circuit and the first input of the operation circuit; when both switch tubes of the upper bridge arm are turned on, the first switch tube is turned on, and when any switch tube of the upper bridge arm is turned off, the first switch tube is turned off. The second switch circuit includes: a second switch tube and a resistor connected in parallel between the output of the sampling circuit and the second input of the operation circuit; when both switch tubes of the lower bridge arm are turned on, the second switch tube is turned on, and when any switch tube of the lower bridge arm is turned off, the second switch tube is turned off.

[0011] In some other embodiments of the present application, the first switch circuit includes: a first switch tube and a capacitor connected in parallel between the reference voltage output terminal and the first input of the operation circuit, a resistor connected in series between the output of the sampling circuit and the first input of the operation circuit, and the reference voltage output terminal is used to output the reference voltage; when both switch tubes of the upper bridge arm are turned on, the first switch tube is turned off, and when any switch tube of the upper bridge arm is turned off, the first switch tube is turned on. The second switch circuit includes: a second switch tube and a capacitor connected in parallel between the reference voltage output terminal and the second input of the operation circuit, and a resistor connected in series between the output of the sampling circuit and the second input of the operation circuit; when both switch tubes of the lower bridge arm are turned on, the second switch tube is turned off, and when any switch tube of the lower bridge arm is turned off, the second switch tube is turned on.

[0012] In some embodiments of the present application, the sampling circuit has a first output and a second output, the first output is used to output a first sampling voltage, the second output is used to output a second sampling voltage, and the first sampling voltage and the second sampling voltage are differential voltages. The first switch circuit is connected between the first output of the sampling circuit and the first input of the operation circuit, and the second switch circuit is connected between the second output of the sampling circuit and the second input of the operation circuit.

[0013] In some embodiments of the present application, the operational circuit includes an operational amplifier, and a plurality of resistors and a plurality of capacitors. The plurality of resistors and the plurality of capacitors include: a resistor connected in series between a first input of the operational circuit and a positive input terminal of the operational amplifier, another resistor connected in series between a second input of the operational circuit and a negative input terminal of the operational amplifier, another resistor and a capacitor connected in parallel between a reference voltage output terminal and a positive input terminal of the operational amplifier, another resistor and a capacitor connected in parallel between a negative input terminal of the operational amplifier and an output terminal of the operational amplifier, the output terminal of the operational amplifier serving as an output of the operational circuit, and the reference voltage output terminal being used to output a reference voltage.

[0014] In some other embodiments of the present application, the operational circuit includes: an operational amplifier, and multiple resistors and multiple capacitors. The multiple resistors and multiple capacitors include: a resistor connected in series between the first input of the operational circuit and the positive input terminal of the operational amplifier, another resistor connected in series between the second input of the operational circuit and the positive input terminal of the operational amplifier, another resistor and a capacitor connected in parallel between the reference voltage output terminal and the negative input terminal of the operational amplifier, another resistor and another capacitor connected in parallel between the negative input terminal of the operational amplifier and the output terminal of the operational amplifier, the output terminal of the operational amplifier serves as the output of the operational circuit, and the reference voltage output terminal is used to output the reference voltage.

[0015] In some embodiments of the present application, it also includes: a controller connected to the filter circuit, the controller being used to reconstruct the current at the connection point between the output of the power converter and the AC power grid according to the filtered voltage difference.

[0016] In some embodiments of the present application, the filtering circuit can be integrated into the controller.

[0017] In other embodiments of the present application, the filter circuit and the controller may be provided independently of each other, that is, provided in different circuit boards.

[0018] In some embodiments of the present application, the primary circuit includes: a first bridge arm and a second bridge arm connected in parallel, the first bridge arm and the second bridge arm both include an upper bridge arm and a lower bridge arm, the connection point of the upper bridge arm and the lower bridge arm of the first bridge arm is the midpoint of the first bridge arm, and the connection point of the upper bridge arm and the lower bridge arm of the second bridge arm is the midpoint of the second bridge arm; the midpoint of the first bridge arm is connected to one end of the primary winding of the transformer, and the midpoint of the second bridge arm is connected to the other end of the primary winding of the transformer.

[0019] In a second aspect, the present application provides an output current reconstruction method for a power converter, comprising: controlling a sampling circuit to collect the resonant current of a transformer of the power converter and outputting a sampling voltage; the sampling circuit is located between the transformer and the secondary circuit, or the sampling circuit is located between the transformer and the primary circuit; when the two switch tubes of the upper bridge arm of the secondary circuit are both turned on, controlling the first switch circuit to output the sampling voltage to the operation circuit, and when any switch tube of the upper bridge arm of the secondary circuit is turned off, controlling the first switch circuit to output a reference voltage to the operation circuit, the reference voltage is a fixed value, and the first switch circuit is connected between the output of the sampling circuit and the first input of the operation circuit; when the two switch tubes of the lower bridge arm of the secondary circuit are both turned on, controlling the second switch circuit to output the sampling voltage to the operation circuit, and when any switch tube of the lower bridge arm of the secondary circuit is turned off, controlling the second switch circuit to output the reference voltage to the operation circuit, and the second switch circuit is connected between the output of the sampling circuit and the second input of the operation circuit; controlling the operation circuit to output the voltage difference between the voltages received by the first input and the second input of the operation circuit; and controlling the filter circuit to filter the voltage difference output by the operation circuit.

[0020] In the present application, there is no need to add an additional sampling circuit on the output side. The resonant current obtained by sampling the existing current sensor, i.e., the sampling circuit, disposed between the transformer and the secondary circuit can be used, and combined with the working state of the switch tube in the secondary circuit to reconstruct the output current of the power converter, thereby reducing the number of hardware components, reducing costs, and enhancing product competitiveness.

[0021] Specifically, when determining the relationship between the output current and the resonant current, the different states of the bridge arm of the secondary circuit in the conduction time and the dead time are integrated, and the working states of the first switch circuit and the second switch circuit set between the sampling circuit and the operation circuit in the present application can be configured, so that the working states of the first switch circuit and the second switch circuit depend on the on-off states of the switch tubes in the upper bridge arm and the lower bridge arm of the secondary circuit. Specifically, when the two switch tubes of the upper bridge arm of the secondary bridge arm are both turned on, the first input of the operation circuit receives the sampling voltage, and the second input of the operation circuit receives the reference voltage. The reference voltage can be set to zero voltage, for example, and the operation circuit outputs the difference between the two, so that the reconstructed grid-connected current at this time meets the above relationship. When the two switch tubes of the lower bridge arm of the secondary bridge arm are both turned on, the second input of the operation circuit receives the sampling voltage, and the first input of the operation circuit receives the reference voltage. The operation circuit outputs the difference between the two, so that the reconstructed grid-connected current at this time meets the above relationship. When a switch tube in both the upper bridge arm and the lower bridge arm of the secondary bridge arm is turned on, the first input of the operation circuit receives the reference voltage, the second input of the operation circuit receives the reference voltage, and the operation circuit outputs the difference between the two, that is, zero voltage, so that the reconstructed grid-connected current at this time meets the above relationship. In summary, by configuring the working states of the first switch circuit and the second switch circuit, the output voltage of the operation circuit can meet the characteristics of the actual output current of the bridge arm of the secondary circuit during the conduction time and the dead time, and the accuracy of the reconstructed output current can be improved.

[0022] In some embodiments of the present application, the method specifically includes: when both switch tubes of the upper bridge arm of the secondary circuit are turned on, the first switch tube in the first switch circuit is controlled to be turned on; when any switch tube of the upper bridge arm of the secondary circuit is turned off, the first switch tube is controlled to be turned off, and the first switch tube is connected in series between the output of the sampling circuit and the first input of the operation circuit. When both switch tubes of the lower bridge arm of the secondary circuit are turned on, the second switch tube in the second switch circuit is controlled to be turned on; when any switch tube of the upper bridge arm of the secondary circuit is turned off, the second switch tube is controlled to be turned off, and the second switch tube is connected in series between the output of the sampling circuit and the second input of the operation circuit.

[0023] In some other embodiments of the present application, it specifically includes: when both switch tubes of the upper bridge arm of the secondary circuit are turned on, the first switch tube in the first switch circuit is controlled to be turned off, and when any switch tube of the upper bridge arm of the secondary circuit is turned off, the first switch tube is controlled to be turned on, and the first switch tube is connected in series between the reference voltage output terminal and the first input of the operation circuit. When both switch tubes of the lower bridge arm of the secondary circuit are turned on, the second switch tube in the second switch circuit is controlled to be turned off, and when any switch tube of the lower bridge arm of the secondary circuit is turned off, the second switch tube is controlled to be turned on, and the second switch tube is connected in series between the reference voltage output terminal and the second input of the operation circuit.

[0024] In some embodiments of the present application, it also includes: controlling the controller to reconstruct the current at the connection point between the output of the power converter and the AC grid according to the filtered voltage difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a photovoltaic system;

[0026] Figure 2 A schematic diagram of the structure of a power converter provided in an embodiment of the present application;

[0027] Figure 3a A schematic diagram of an operating condition of a secondary circuit of a power converter provided in an embodiment of the present application;

[0028] Figure 3b A schematic diagram of another operating condition of the secondary circuit of the power converter provided in an embodiment of the present application;

[0029] Figure 3c A schematic diagram of another operating condition of the secondary circuit of the power converter provided in an embodiment of the present application;

[0030] Figure 3d A schematic diagram of another operating condition of the secondary circuit of the power converter provided in an embodiment of the present application;

[0031] Figure 4 A schematic diagram of a structure of a reconstruction circuit of a power converter provided in an embodiment of the present application;

[0032] Figure 5 Another structural schematic diagram of a reconstruction circuit of a power converter provided in an embodiment of the present application;

[0033] Figure 6 Another structural schematic diagram of a reconstruction circuit of a power converter provided in an embodiment of the present application;

[0034] Figure 7 Another structural schematic diagram of a reconstruction circuit of a power converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as being limited to the embodiments described herein; on the contrary, these embodiments are provided to make the present application more comprehensive and complete, and to fully convey the concepts of the example embodiments to those skilled in the art. The same figure marks in the figures represent the same or similar structures, and thus their repeated descriptions will be omitted. The words expressing position and direction described in this application are all explained using the accompanying drawings as examples, but changes may be made as needed, and all changes are included in the scope of protection of this application. The drawings of this application are only used to illustrate the relative position relationship and do not represent the true proportions.

[0036] It should be noted that specific details are described in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in a variety of other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific implementation methods disclosed below. The subsequent description of the specification is a preferred implementation method for implementing the present application, but the description is for the purpose of illustrating the general principles of the present application and is not intended to limit the scope of the present application. The scope of protection of the present application shall be determined by the definition of the attached claims.

[0037] In order to facilitate understanding of the embodiments of the present application, the relevant technologies involved in the embodiments of the present application are first introduced below.

[0038] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to be used as limitations on the present application. As used in the specification and appended claims of the present application, the singular expressions "one", "a kind of" and "the" are intended to also include expressions such as "one or more", unless there is a clear indication to the contrary in the context. It should also be understood that in the following embodiments of the present application, "at least one" refers to one, two or more than two.

[0039] References to "one embodiment" and the like described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application. Thus, the phrases "in one embodiment", "in some embodiments", "in other embodiments", etc. that appear at different places in this specification do not necessarily all refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0040] Reference Figure 1,A photovoltaic system generally includes photovoltaic modules and micro-inverters. The input of the micro-inverter is connected to the photovoltaic modules as a DC power source, and the output of the micro-inverter is connected to the grid / load through power lines. The micro-inverter is used as a power converter to convert the energy provided by the photovoltaic modules into AC power and output it to the grid or load.

[0041] At present, the grid-connected current is generally obtained by adding a current sensor on the output side of the micro-inverter and directly sampling the output current of the micro-inverter using the current sensor. It is necessary to add additional hardware resources such as current sensors on the output side, which will increase the sampling cost. In view of the above problems, the embodiment of the present application solves the problem of output current reconstruction of the power converter. Based on the resonant current in the power converter and the working state of the switch tube in the secondary circuit, the output current of the power converter, i.e., the grid-connected current, is reconstructed.

[0042] Reference Figure 2 , the power converter provided in the embodiment of the present application includes: a transformer T, a primary circuit, a secondary circuit, a sampling circuit, a first switching circuit, a second switching circuit, an operation circuit and a filtering circuit. Among them, the input of the power converter is used to connect to a DC power supply, which can be a storage battery or a photovoltaic module, and the output of the power converter is used to connect to an AC power grid. The primary circuit is connected between the input of the power converter and the transformer T, that is, one end of the primary circuit is connected to the DC power supply and is used to input a DC voltage, and the other end of the primary circuit is connected to the primary winding of the transformer T. The primary circuit is used to convert the input DC voltage into a high-frequency AC rectangular wave signal. The transformer T is specifically a high-frequency transformer, and the high-frequency transformer has a turns ratio of 1:N. The transformer T is mainly used to achieve voltage conversion and electrical isolation. The transformer T can be designed as a transformer with a secondary leakage inductance equal to Lr, so that the inductive device Lr connected in series with the secondary winding of the transformer T can be the secondary leakage inductance of the transformer T. Alternatively, the power converter may also include an inductive device Lr, that is, the transformer T may also be designed as a high-frequency transformer with very small leakage inductance, and a separate inductive device Lr connected in series may be provided. The inductive device Lr may be used as a resonant inductor and a resonant capacitor to form a resonant element, and the resonant element is used to assist the transformer T in achieving soft switching control. The secondary circuit is connected between the transformer T and the output of the power converter, that is, one end of the secondary circuit is used to output an AC voltage, and the other end of the secondary circuit is connected to the secondary winding of the transformer T. When the inductive device Lr is present, the other end of the secondary circuit is connected in series with the inductive device Lr. sThen connect the secondary winding of transformer T. The secondary circuit is used to convert the high-frequency AC rectangular wave signal into an AC voltage output, and the output end of the secondary circuit can be connected to the power grid or load. The power converter generally also includes an electromagnetic interference (EMI) filter arranged on the AC side, that is, an EMI filter is connected between the secondary circuit and the output of the power converter, and the EMI filter is used to suppress differential mode and common mode noise.

[0043] Specifically, in the present application, the primary circuit can be a full-bridge circuit, specifically including: a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4. In the full-bridge circuit, the first switch tube S1 and the second switch tube S2 are connected in series to form a first bridge arm, and the third switch tube S3 and the fourth switch tube S4 are connected in series to form a second bridge arm. The first bridge arm and the second bridge arm are connected in parallel, and the connection point of the first switch tube S1 and the second switch tube S2 is connected to one end of the primary winding of the transformer 2 as the midpoint of the first bridge arm, and the connection point of the third switch tube S3 and the fourth switch tube S4 is connected to the other end of the primary winding of the transformer 2 as the midpoint of the second bridge arm. Alternatively, the primary circuit 1 can be a half-bridge circuit or any other circuit that can realize the conversion of direct current into a high-frequency alternating rectangular wave signal. The controller can control the first switch tube S1 and the second switch tube S2 to be complementary and turned on at high frequency, and control the third switch tube S3 and the fourth switch tube S4 to be complementary and turned on at high frequency, so that the primary circuit 1 converts the input direct current voltage into a high-frequency alternating rectangular wave signal and outputs it to the primary winding of the transformer.

[0044] Specifically, in the present application, the secondary circuit is generally a half-bridge circuit, which may specifically include a third bridge arm, and the third bridge arm includes an upper bridge arm and a lower bridge arm. The upper bridge arm may be composed of a bidirectional switch, and the lower bridge arm may be composed of a bidirectional switch, and both the upper bridge arm and the lower bridge arm include two switch tubes with opposite freewheeling directions. The connection point of the two bidirectional switches, i.e., the connection point of the upper bridge arm and the lower bridge arm, is used as the midpoint of the third bridge arm, and the inductive device Lr may be connected in series to one end of the secondary winding of the transformer T. Specifically, the upper bridge arm or the lower bridge arm in the secondary circuit may be composed of two discretely arranged switch tubes, or may be composed of a module integrated with two switch tubes, or may be composed of a monolithic bidirectional (conduction or blocking) device (e.g., a monolithic bidirectional GaN device). For example, the upper bridge arm includes a fifth switch tube S5 and a sixth switch tube S6 connected in series, and the lower bridge arm includes a seventh switch tube S7 and an eighth switch tube S8 connected in series. Specifically, the two ports of each switch tube connected to the power circuit may be defined as port 1 and port 2, respectively. When the switch tube is turned on, the current can flow in from port 1 and out from port 2, or flow in from port 2 and out from port 1; when the switch tube is in the freewheeling state, the current flows in from port 2 and out from port 1. The freewheeling directions of the sixth switch tube S6 and the seventh switch tube S7 can be defined as pointing to the connection point between the upper bridge arm and the lower bridge arm, and the freewheeling directions of the fifth switch tube S5 and the eighth switch tube S8 can be defined as pointing away from the connection point between the upper bridge arm and the lower bridge arm. In the upper bridge arm and the lower bridge arm, the switch tube connected to one end of the secondary winding can be defined as the inner switch tube, and the switch tube connected to the AC voltage can be defined as the outer switch tube. The inner switch tube is connected between the outer switch tube and the inductive device Lr (which can also be considered as the connection point between the upper bridge arm and the lower bridge arm), that is Figure 2 The sixth switch tube S6 and the seventh switch tube S7 are inner switches, and the fifth switch tube S5 and the eighth switch tube S8 are outer switches. In the upper bridge arm and the lower bridge arm, the port 2 of the outer switch tube can be connected to the port 1 of the inner switch tube, so that the freewheeling direction of the two switch tubes in the upper bridge arm or the lower bridge arm points to the direction away from the connection point of the two switch tubes. Alternatively, in the upper bridge arm and the lower bridge arm, the port 1 of the outer switch tube can also be connected to the port 2 of the inner switch tube, so that the freewheeling direction of the two switch tubes in an upper bridge arm or a lower bridge arm points to the direction of the connection point of the two switch tubes. In addition, the connection method of the switch tubes in the upper bridge arm and the lower bridge arm in the half-bridge circuit can be the same or different.

[0045] Reference Figure 2 In the present application, the secondary circuit may further include a first capacitor C r1 and the second capacitor C r2 The first capacitor C r1 and the second capacitor C r2 It can be used as a resonant capacitor to form a resonant element with the inductive device Lr. The first capacitor C r1and the second capacitor C r2 It can also be used as a voltage divider capacitor. The first capacitor C r1 and the second capacitor C r2 After being connected in series, the first capacitor C r1 and the second capacitor C r2 The connection point is connected to the other end of the secondary winding of the transformer T.

[0046] Reference Figure 2 , due to the resonant current i output by transformer T r In order to avoid the problem of overcurrent, a high-speed current sensor is currently set between the transformer T and the secondary circuit to measure the resonant current i r In this application, there is no need to add an additional sampling circuit on the output side. The resonant current i obtained by sampling the current sensor is r , combined with the working state of the switch tube in the secondary circuit, the output current i of the power converter can be controlled g Reconstruction can reduce the number of hardware components, lower costs and enhance product competitiveness.

[0047] Specifically, the sampling circuit can be located between the transformer T and the secondary circuit, or the sampling circuit can also be located between the transformer T and the primary circuit. The sampling circuit is used to collect the resonant current i of the transformer T. r , and output the sampling voltage V i .

[0048] Reference Figure 2 In the present application, the first switch circuit is connected between the output of the sampling circuit and the first input of the operation circuit. The first switch circuit is used to output a sampling voltage to the operation circuit when both switch tubes of the upper bridge arm are turned on, and to output a reference voltage to the operation circuit when any switch tube of the upper bridge arm is turned off. The reference voltage is a fixed value. The second switch circuit is connected between the output of the sampling circuit and the second input of the operation circuit. The second switch circuit is used to output a sampling voltage to the operation circuit when both switch tubes of the lower bridge arm are turned on, and to output a reference voltage to the operation circuit when any switch tube of the lower bridge arm is turned off. The operation circuit is used to output the voltage difference between the first input and the second input receiving voltage of the operation circuit, and the voltage difference can reconstruct the output current i0 of the power converter before the EMI filter.

[0049] Reference Figure 2 In the present application, the filter circuit is connected to the output of the operation circuit, and the filter circuit is used to filter the voltage difference output by the operation circuit to filter out the high-frequency signal. The output voltage of the filter circuit can reconstruct the output current i after passing through the EMI filter of the power converter. gSpecifically, the output of the filter circuit is connected to the controller, and the controller can map the output voltage of the filter circuit to a current according to a set mapping relationship, and the current can reconstruct the current at the connection point between the output of the power converter and the AC grid, that is, the grid-connected current. The filter circuit and the controller can be set independently of each other, that is, set in different circuit boards, or the filter circuit can be integrated in the controller. In this application, reference is made to Figure 3a , the output current i0 of the secondary circuit and the resonant current i r The relationship is i0=0.5i r ; and, with reference to Figure 3b , the output current i0 of the secondary circuit and the resonant current i r The relationship is i0 = -0.5i r . Reference Figure 3c , in the secondary circuit, the fifth switch tube S5 and the seventh switch tube S7 are in the off state, and, referring to Figure 3d When the sixth switch tube S6 and the eighth switch tube S8 in the secondary circuit are in the off state, it can be considered that the secondary circuit is in the dead time, and the resonant current i r The current is diverted to the upper and lower arms of the secondary circuit to realize the charging and discharging of the parasitic capacitors respectively. At this time, the output current i0 = 0. Through the above analysis, the comprehensive expression between the output current i0 of the secondary circuit and the conduction state of the switch tube in the secondary circuit can be obtained: i0 = 0.5i r [(S5&S6)-(S7&S8)].

[0050] Based on the above analysis, the output current i0 and the resonant current i rThe relationship integrates the different states of the bridge arm of the secondary circuit during the conduction time and the dead time, and the working states of the first switch circuit and the second switch circuit set between the sampling circuit and the operation circuit in the present application can be configured so that the working states of the first switch circuit and the second switch circuit depend on the on-off states of the switch tubes in the upper bridge arm and the lower bridge arm of the secondary circuit. Specifically, when the two switch tubes of the upper bridge arm of the secondary bridge arm are both turned on, the first input of the operation circuit receives the sampling voltage, and the second input of the operation circuit receives the reference voltage. The reference voltage can be set to zero voltage, for example, and the operation circuit outputs the difference between the two, so that the reconstructed grid-connected current at this time meets the above relationship. When the two switch tubes of the lower bridge arm of the secondary bridge arm are both turned on, the second input of the operation circuit receives the sampling voltage, and the first input of the operation circuit receives the reference voltage. The operation circuit outputs the difference between the two, so that the reconstructed grid-connected current at this time meets the above relationship. When a switch tube in both the upper bridge arm and the lower bridge arm of the secondary bridge arm is turned on, the first input of the operation circuit receives the reference voltage, the second input of the operation circuit receives the reference voltage, and the operation circuit outputs the difference between the two, that is, zero voltage, so that the reconstructed grid-connected current at this time meets the above relationship. In summary, by configuring the working states of the first switch circuit and the second switch circuit, the output voltage of the operation circuit can meet the characteristics of the actual output current of the bridge arm of the secondary circuit during the conduction time and the dead time, and the accuracy of the reconstructed output current can be improved.

[0051] In the present application, specific circuit topologies of the first switch circuit and the second switch circuit may be configured based on the above formula.

[0052] Reference Figure 4 In some embodiments of the present application, the first switch circuit may specifically include: a first switch K1 connected in series between the output of the sampling circuit and the first input of the operation circuit, and a resistor connected in series between the reference voltage output terminal and the first input of the operation circuit, the reference voltage output terminal being used to output the reference voltage V ref When the two switch tubes of the upper bridge arm of the secondary circuit, namely the fifth switch tube S5 and the sixth switch tube S6, are both turned on, the first switch K1 is turned on, and the input voltage V1 of the first input of the operation circuit is the sampling voltage V i , which can characterize the resonant current i r When at least one of the switch tubes of the upper bridge arm of the secondary circuit, namely the fifth switch tube S5 and the sixth switch tube S6, is turned off, the first switch K1 is turned off, and the input voltage V1 of the first input of the operation circuit is the reference voltage V provided by the reference voltage output terminal. refThe second switch circuit may specifically include: a second switch K2 connected in series between the output of the sampling circuit and the second input of the operation circuit, and a resistor connected in series between the reference voltage output terminal and the second input of the operation circuit. When the two switch tubes of the lower bridge arm of the secondary circuit, namely the seventh switch tube S7 and the eighth switch tube S8, are both turned on, the second switch K2 is turned on, and the input voltage V2 of the second input of the operation circuit is the sampling voltage V i , which can characterize the resonant current i r When at least one of the switch tubes of the lower bridge arm, namely the seventh switch tube S7 and the eighth switch tube S8, is turned off, the second switch K2 is turned off, and the input voltage V2 of the second input of the operation circuit is the reference voltage V provided by the reference voltage output terminal. ref The operation circuit may include a subtractor, and the operation circuit is used to calculate the difference between the input voltage V1 of the first input and the input voltage V2 of the second input, that is, the output voltage V o is the difference between V1 and V2, and the output voltage V o It can represent the output current i0 of the secondary circuit. The output voltage V o After filtering, the grid-connected current i of the power converter can be reconstructed. g .

[0053] Reference Figure 5 In some other embodiments of the present application, the first switch circuit may specifically include: a first switch K1 and a resistor connected in parallel between the output of the sampling circuit and the first input of the operation circuit. When the two switch tubes of the upper bridge arm of the secondary circuit, namely the fifth switch tube S5 and the sixth switch tube S6, are both turned on, the first switch K1 is turned on, and the input voltage V1 of the first input of the operation circuit is the sampling voltage V i , which can characterize the resonant current i r When at least one of the switch tubes of the upper bridge arm of the secondary circuit, namely the fifth switch tube S5 and the sixth switch tube S6, is turned off, the first switch K1 is turned off, and the input voltage V1 of the first input of the operation circuit is equivalent to the reference voltage V ref The second switch circuit may specifically include: a second switch K2 and a resistor connected in parallel between the output of the sampling circuit and the second input of the operation circuit. When the two switch tubes of the lower bridge arm of the secondary circuit, namely the seventh switch tube S7 and the eighth switch tube S8, are both turned on, the second switch K2 is turned on, and the input voltage V2 of the second input of the operation circuit is the sampling voltage V i , which can characterize the resonant current i r When at least one of the switch tubes of the lower bridge arm, namely the seventh switch tube S7 and the eighth switch tube S8, is turned off, the second switch K2 is turned off, and the input voltage V2 of the second input of the operation circuit is equivalent to the reference voltage V refThe operation circuit is used to calculate the difference between the input voltage V1 of the first input and the input voltage V2 of the second input, that is, the output voltage V o is the difference between V1 and V2, and the output voltage V o It can represent the output current i0 of the secondary circuit. The output voltage V o After filtering, the grid-connected current i of the power converter can be reconstructed. g .

[0054] Reference Figure 6 In some other embodiments of the present application, the first switch circuit may specifically include: a first switch K1 and a capacitor connected in parallel between the reference voltage output terminal and the first input of the operation circuit, and a resistor connected in series between the output of the sampling circuit and the first input of the operation circuit. When the two switch tubes of the upper bridge arm of the secondary circuit, namely the fifth switch tube S5 and the sixth switch tube S6, are both turned on, the first switch K1 is turned off, and the input voltage V1 of the first input of the operation circuit is the sampling voltage V i , which can characterize the resonant current i r When at least one of the switch tubes of the upper bridge arm of the secondary circuit, namely the fifth switch tube S5 and the sixth switch tube S6, is turned off, the first switch K1 is turned on, and the input voltage V1 of the first input of the operation circuit is the reference voltage V provided by the reference voltage output terminal. ref The second switch circuit may specifically include: a second switch K2 and a capacitor connected in parallel between the reference voltage output terminal and the second input of the operation circuit, and a resistor connected in series between the output of the sampling circuit and the second input of the operation circuit. When the two switch tubes of the lower bridge arm of the secondary circuit, namely the seventh switch tube S7 and the eighth switch tube S8, are both turned on, the second switch K2 is turned off, and the input voltage V2 of the second input of the operation circuit is the sampling voltage V i , which can characterize the resonant current i r When at least one of the switch tubes of the lower bridge arm, namely the seventh switch tube S7 and the eighth switch tube S8, is turned off, the second switch K2 is turned on, and the input voltage V2 of the second input of the operation circuit is the reference voltage V provided by the reference voltage output terminal. ref The operation circuit is used to calculate the difference between the input voltage V1 of the first input and the input voltage V2 of the second input, that is, the output voltage V o is the difference between V1 and V2, and the output voltage V o It can represent the output current i0 of the secondary circuit. The output voltage V o After filtering, the grid-connected current i of the power converter can be reconstructed. g .

[0055] Reference Figures 4 to 6In some embodiments of the present application, the output of the sampling circuit can be divided into two, connected to the first switch circuit and the second switch circuit respectively.

[0056] Reference Figure 7 In some other embodiments of the present application, the sampling circuit may have a first output and a second output, and the first output is used to output a first sampling voltage V i1 The second output is used to output the second sampling voltage V i2 , the first sampling voltage V i1 and the second sampling voltage V i2 The first switch circuit is connected between the first output of the sampling circuit and the first input of the operation circuit, and the second switch circuit is connected between the second output of the sampling circuit and the second input of the operation circuit. The first switch circuit is used to output the first sampling voltage to the operation circuit when both switch tubes of the upper bridge arm are turned on; the second switch circuit is used to output the second sampling voltage to the operation circuit when both switch tubes of the lower bridge arm are turned on.

[0057] Reference Figures 4 to 6 In some embodiments of the present application, the operational circuit includes an operational amplifier, and a plurality of resistors and a plurality of capacitors. The plurality of resistors and the plurality of capacitors include: a resistor R connected in series between the first input of the operational circuit and the positive input terminal of the operational amplifier; i , a resistor R connected in series between the second input of the operational circuit and the negative input terminal of the operational amplifier i , a resistor R connected in parallel between the reference voltage output and the positive input of the operational amplifier o and capacitor C o , a resistor R connected in parallel between the negative input terminal of the operational amplifier and the output terminal of the operational amplifier o and capacitor C o , the capacitors in parallel can achieve a certain filtering effect. The output of the operational amplifier is used as the output of the operational circuit.

[0058] Reference Figure 7 In some other embodiments of the present application, the operational circuit includes an operational amplifier, and a plurality of resistors and a plurality of capacitors. The plurality of resistors and the plurality of capacitors include: a resistor R connected in series between the first input of the operational circuit and the positive input terminal of the operational amplifier; i , a resistor R connected in series between the second input of the operational circuit and the non-inverting input terminal of the operational amplifier i , a resistor R connected in parallel between the reference voltage output and the negative input of the operational amplifier o and capacitor C o , a resistor R connected in parallel between the negative input terminal of the operational amplifier and the output terminal of the operational amplifier o and capacitor Co , the capacitors in parallel can achieve a certain filtering effect. The output of the operational amplifier is used as the output of the operational circuit.

[0059] Based on the same inventive concept, the embodiment of the present application also provides an output current reconstruction method of a power conversion circuit, comprising the following steps:

[0060] The sampling circuit is controlled to collect the resonant current of the transformer of the power converter and output a sampled voltage. The sampling circuit can be located between the transformer and the secondary circuit, or between the transformer and the primary circuit.

[0061] When both switch tubes of the upper bridge arm of the secondary circuit are turned on, the first switch circuit can be controlled to output a sampling voltage to the operation circuit; when any switch tube of the upper bridge arm of the secondary circuit is turned off, the first switch circuit can be controlled to output a reference voltage to the operation circuit, and the reference voltage is a fixed value. The first switch circuit is connected between the output of the sampling circuit and the first input of the operation circuit.

[0062] When both switch tubes of the lower bridge arm of the secondary circuit are turned on, the second switch circuit can be controlled to output a sampling voltage to the operation circuit; when any switch tube of the lower bridge arm of the secondary circuit is turned off, the second switch circuit can be controlled to output a reference voltage to the operation circuit. The second switch circuit is connected between the output of the sampling circuit and the second input of the operation circuit.

[0063] The control operation circuit outputs the voltage difference between the first input and the second input receiving voltage of the operation circuit, and controls the filter circuit to filter the voltage difference output by the operation circuit to filter out the high-frequency signal. The output voltage of the filter circuit can reconstruct the output current i after passing through the EMI filter of the power converter. g .

[0064] In the present application, the control controller may also reconstruct the output current i of the power converter output and the AC grid connection point according to the filtered voltage difference. g .

[0065] In some embodiments of the present application, when the first switch circuit and the second switch circuit adopt Figure 4 and Figure 5When the circuit topology is , when both switch tubes of the upper bridge arm of the secondary circuit are turned on, the first switch tube in the first switch circuit is controlled to be turned on, and when any switch tube of the upper bridge arm of the secondary circuit is turned off, the first switch tube is controlled to be turned off, and the first switch tube is connected in series between the output of the sampling circuit and the first input of the operation circuit. When both switch tubes of the lower bridge arm of the secondary circuit are turned on, the second switch tube in the second switch circuit is controlled to be turned on, and when any switch tube of the upper bridge arm of the secondary circuit is turned off, the second switch tube is controlled to be turned off, and the second switch tube is connected in series between the output of the sampling circuit and the second input of the operation circuit.

[0066] In some other embodiments of the present application, when the first switch circuit and the second switch circuit adopt a method such as Figure 6 When the circuit topology is , when both switch tubes of the upper bridge arm of the secondary circuit are turned on, the first switch tube in the first switch circuit is controlled to be turned off, and when any switch tube of the upper bridge arm of the secondary circuit is turned off, the first switch tube is controlled to be turned on, and the first switch tube is connected in series between the reference voltage output terminal and the first input of the operation circuit. When both switch tubes of the lower bridge arm of the secondary circuit are turned on, the second switch tube in the second switch circuit is controlled to be turned off, and when any switch tube of the lower bridge arm of the secondary circuit is turned off, the second switch tube is controlled to be turned on, and the second switch tube is connected in series between the reference voltage output terminal and the second input of the operation circuit.

[0067] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A power converter, characterized in that: include: A transformer, a primary circuit, a secondary circuit, a sampling circuit, a first switch circuit, a second switch circuit, an operation circuit and a filter circuit; The input of the power converter is used to be connected to a DC power supply, the output of the power converter is used to be connected to an AC power grid, the primary circuit is connected between the input of the power converter and the transformer, and the secondary circuit is connected between the transformer and the output of the power converter; The secondary circuit includes a bridge arm, a first capacitor and a second capacitor, the bridge arm includes an upper bridge arm and a lower bridge arm, the upper bridge arm includes two switch tubes with opposite freewheeling directions, the lower bridge arm includes two switch tubes with opposite freewheeling directions, the connection point of the upper half bridge arm and the lower half bridge arm is connected to one end of the secondary winding of the transformer, the first capacitor and the second capacitor are connected in series and then connected in parallel with the bridge arm, and the connection point of the first capacitor and the second capacitor is connected to the other end of the secondary winding of the transformer; The sampling circuit is located between the transformer and the secondary circuit, or the sampling circuit is located between the transformer and the primary circuit, and the sampling circuit is used to collect the resonant current of the transformer and output a sampling voltage; The first switch circuit is connected between the output of the sampling circuit and the first input of the operation circuit, and is used to output the sampling voltage to the operation circuit when both switch tubes of the upper bridge arm are turned on, and output a reference voltage to the operation circuit when any switch tube of the upper bridge arm is turned off, and the reference voltage is a fixed value; The second switch circuit is connected between the output of the sampling circuit and the second input of the operation circuit, and is used to output the sampling voltage to the operation circuit when both switch tubes of the lower bridge arm are turned on, and output the reference voltage to the operation circuit when any switch tube of the lower bridge arm is turned off; The operation circuit is used to output a voltage difference between a first input and a second input receiving voltage of the operation circuit; The filter circuit is connected to the operation circuit, and the filter circuit is used to filter the voltage difference.

2. The power converter according to claim 1, characterized in that The first switch circuit comprises: a first switch tube connected in series between the output of the sampling circuit and the first input of the operation circuit, and a resistor connected in series between a reference voltage output terminal and the first input of the operation circuit, wherein the reference voltage output terminal is used to output the reference voltage; when both the switch tubes of the upper bridge arm are turned on, the first switch tube is turned on, and when any of the switch tubes of the upper bridge arm is turned off, the first switch tube is turned off; The second switching circuit includes: a second switching tube connected in series between the output of the sampling circuit and the second input of the operation circuit, and a resistor connected in series between the reference voltage output terminal and the second input of the operation circuit; when both switching tubes of the lower bridge arm are turned on, the second switching tube is turned on, and when any switching tube of the lower bridge arm is turned off, the second switching tube is turned off.

3. The power converter according to claim 1, characterized in that: The first switch circuit comprises: a first switch tube and a resistor connected in parallel between the output of the sampling circuit and the first input of the operation circuit; when both the switch tubes of the upper bridge arm are turned on, the first switch tube is turned on, and when any switch tube of the upper bridge arm is turned off, the first switch tube is turned off; The second switch circuit includes: a second switch tube and a resistor connected in parallel between the output of the sampling circuit and the second input of the operation circuit; when both switch tubes of the lower bridge arm are turned on, the second switch tube is turned on, and when any switch tube of the lower bridge arm is turned off, the second switch tube is turned off.

4. The power converter according to claim 1, characterized in that: The first switch circuit comprises: a first switch tube and a capacitor connected in parallel between a reference voltage output terminal and a first input of the operation circuit, and a resistor connected in series between the output of the sampling circuit and the first input of the operation circuit, and the reference voltage output terminal is used to output the reference voltage; when both switch tubes of the upper bridge arm are turned on, the first switch tube is turned off, and when any switch tube of the upper bridge arm is turned off, the first switch tube is turned on; The second switch circuit includes: a second switch tube and a capacitor connected in parallel between the reference voltage output terminal and the second input of the operation circuit, and a resistor connected in series between the output of the sampling circuit and the second input of the operation circuit; when both switch tubes of the lower bridge arm are turned on, the second switch tube is turned off, and when any switch tube of the lower bridge arm is turned off, the second switch tube is turned on.

5. The power converter according to any one of claims 1 to 4, characterized in that: The sampling circuit has a first output and a second output, the first output is used to output a first sampling voltage, the second output is used to output a second sampling voltage, and the first sampling voltage and the second sampling voltage are differential voltages; The first switch circuit is connected between the first output of the sampling circuit and the first input of the operation circuit, and the second switch circuit is connected between the second output of the sampling circuit and the second input of the operation circuit.

6. The power converter according to any one of claims 1 to 5, characterized in that: The operational circuit includes an operational amplifier, a plurality of resistors and a plurality of capacitors; The multiple resistors and multiple capacitors include: a resistor connected in series between the first input of the operational circuit and the positive input terminal of the operational amplifier, another resistor connected in series between the second input of the operational circuit and the negative input terminal of the operational amplifier, another resistor and a capacitor connected in parallel between the reference voltage output terminal and the positive input terminal of the operational amplifier, another resistor and a capacitor connected in parallel between the negative input terminal of the operational amplifier and the output terminal of the operational amplifier, the output terminal of the operational amplifier serves as the output of the operational circuit, and the reference voltage output terminal is used to output the reference voltage.

7. The power converter according to any one of claims 1 to 5, characterized in that: The operational circuit includes: an operational amplifier, a plurality of resistors and a plurality of capacitors; The multiple resistors and multiple capacitors include: a resistor connected in series between the first input of the operational circuit and the positive input terminal of the operational amplifier, another resistor connected in series between the second input of the operational circuit and the positive input terminal of the operational amplifier, another resistor and a capacitor connected in parallel between the reference voltage output terminal and the negative input terminal of the operational amplifier, another resistor and another capacitor connected in parallel between the negative input terminal of the operational amplifier and the output terminal of the operational amplifier, the output terminal of the operational amplifier serves as the output of the operational circuit, and the reference voltage output terminal is used to output the reference voltage.

8. The power converter according to any one of claims 1 to 7, characterized in that: Also includes: A controller connected to the filter circuit, the controller is used to reconstruct the output of the power converter and the current of the AC power grid connection point according to the filtered voltage difference.

9. The power converter according to claim 8, characterized in that: The filter circuit is integrated in the controller.

10. The power converter according to claim 8, characterized in that The filter circuit and the controller are located in different circuit boards.

11. The power converter according to any one of claims 1 to 10, characterized in that: The primary circuit comprises: a first bridge arm and a second bridge arm connected in parallel, the first bridge arm and the second bridge arm both comprise an upper bridge arm and a lower bridge arm, the connection point of the upper bridge arm and the lower bridge arm of the first bridge arm is the midpoint of the first bridge arm, and the connection point of the upper bridge arm and the lower bridge arm of the second bridge arm is the midpoint of the second bridge arm; The midpoint of the first bridge arm is connected to one end of the primary winding of the transformer, and the midpoint of the second bridge arm is connected to the other end of the primary winding of the transformer.

12. A method for reconstructing output current of a power converter, characterized in that: include: Controlling the sampling circuit to collect the resonant current of the transformer of the power converter and outputting a sampling voltage; The sampling circuit is located between the transformer and the secondary circuit, or the sampling circuit is located between the transformer and the primary circuit; When both switch tubes of the upper bridge arm of the secondary circuit are turned on, the first switch circuit is controlled to output the sampling voltage to the operation circuit; when any switch tube of the upper bridge arm of the secondary circuit is turned off, the first switch circuit is controlled to output a reference voltage to the operation circuit, wherein the reference voltage is a fixed value, and the first switch circuit is connected between the output of the sampling circuit and the first input of the operation circuit; When both switch tubes of the lower bridge arm of the secondary circuit are turned on, the second switch circuit is controlled to output the sampling voltage to the operation circuit; when any switch tube of the lower bridge arm of the secondary circuit is turned off, the second switch circuit is controlled to output the reference voltage to the operation circuit, and the second switch circuit is connected between the output of the sampling circuit and the second input of the operation circuit; Controlling the operation circuit to output a voltage difference between a first input and a second input receiving voltage of the operation circuit; The control filter circuit filters the voltage difference output by the operation circuit.

13. The method according to claim 12, characterized in that Specifically include: When both switch tubes of the upper bridge arm of the secondary circuit are turned on, the first switch tube in the first switch circuit is controlled to be turned on; when any switch tube of the upper bridge arm of the secondary circuit is turned off, the first switch tube is controlled to be turned off, and the first switch tube is connected in series between the output of the sampling circuit and the first input of the operation circuit; When both switch tubes of the lower bridge arm of the secondary circuit are turned on, the second switch tube in the second switch circuit is controlled to be turned on; when any switch tube of the upper bridge arm of the secondary circuit is turned off, the second switch tube is controlled to be turned off, and the second switch tube is connected in series between the output of the sampling circuit and the second input of the operation circuit.

14. The method according to claim 12, characterized in that Specifically include: When both switch tubes of the upper bridge arm of the secondary circuit are turned on, the first switch tube in the first switch circuit is controlled to be turned off, and when any switch tube of the upper bridge arm of the secondary circuit is turned off, the first switch tube is controlled to be turned on, and the first switch tube is connected in series between the reference voltage output terminal and the first input of the operation circuit; When both switch tubes of the lower bridge arm of the secondary circuit are turned on, the second switch tube in the second switch circuit is controlled to be turned off; when any switch tube of the lower bridge arm of the secondary circuit is turned off, the second switch tube is controlled to be turned on, and the second switch tube is connected in series between the reference voltage output terminal and the second input of the operational circuit.

15. The method according to any one of claims 12 to 14, characterized in that: Also includes: The control controller reconstructs the current at the connection point between the output of the power converter and the AC grid according to the filtered voltage difference.

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