Current control method in inverter circuit and inverter circuit

Abstract

The invention provides a current control method in an inverter circuit and the inverter circuit, the inverter circuit comprises a primary side bridge circuit, a coupling inductor and a secondary side bridge circuit, the primary side bridge circuit is connected with the secondary side bridge circuit through the coupling inductor, the coupling inductor comprises a primary side winding and a secondary side winding, the voltage acting on the primary side winding is the primary side voltage, and the voltage acting on the secondary side winding is the secondary side voltage. Voltage acting on the secondary winding is secondary voltage, both the primary bridge circuit and the secondary bridge circuit comprise switching devices, and the current control method comprises the steps that the switching devices of the primary bridge circuit and the switching devices of the secondary bridge circuit are controlled; and the phase angles of the primary side bridge circuit and the secondary side bridge circuit are adjusted, so that the current flowing through the coupling inductor is zero at the turn-off moment of the switching device, and when the current flowing through the coupling inductor is zero, the turn-off current flowing through the switching device is zero. By adjusting the phase angles of the primary side bridge circuit and the secondary side bridge circuit, zero-current turn-off of the switching device is achieved, the hard turn-off phenomenon is avoided, and the system efficiency is remarkably improved.

Description

Technical Field

[0001] This application relates to the field of inverter circuits, and more particularly to a current control method and an inverter circuit. Background Technology

[0002] Currently, inverters are an important power conversion device that can convert direct current (DC) into alternating current (AC) and are widely used in various power supply and electrical equipment.

[0003] Optimizing inverter efficiency is a core issue in engineering applications. Related technologies can optimize inverter efficiency through methods such as reducing the effective current value, reducing return power, and reducing overall system losses. Reducing the effective current value is a relatively direct approach, but the mathematical model used in this optimization scheme is overly complex and inconvenient for real-time calculation. Optimization schemes based on return power have low efficiency under light loads and limited soft-switching range. Hard turn-off, caused by the switching devices' hard turn-off during inverter operation, leads to overall system losses. Hard turn-off occurs when the switching voltage or current is not zero, resulting in significant energy loss and overall system losses. Soft-switching techniques, including zero-voltage turn-on and zero-current turn-off, can reduce these losses. Zero-voltage turn-on or zero-current turn-off can be achieved when the switching devices are turned off, thereby reducing overall losses caused by the switching devices. Currently, zero-voltage turn-on can be achieved based on different circuit topologies; for example, it can be achieved through parallel parasitic capacitance and inductor resonance. However, while this method reduces the overall losses of the inverter, its implementation requires adjustments to the existing circuit topology and the addition of new electronic components. Summary of the Invention

[0004] In view of this, the embodiments of this application aim to provide a current control method and an inverter circuit in an inverter circuit.

[0005] Firstly, a current control method is provided in an inverter circuit. The inverter circuit includes a primary bridge circuit, a coupling inductor, and a secondary bridge circuit. The primary bridge circuit is connected to the secondary bridge circuit through the coupling inductor. The coupling inductor includes a primary winding and a secondary winding. The voltage acting on the primary winding is the primary voltage, and the voltage acting on the secondary winding is the secondary voltage. Both the primary and secondary bridge circuits include switching devices. The current control method includes: controlling the switching devices of the primary bridge circuit and the secondary bridge circuit; adjusting the phase angle of the primary and secondary bridge circuits so that the current flowing through the coupling inductor is zero at the turn-off moment of the switching device, wherein when the current of the coupling inductor is zero, the turn-off current flowing through the switching device is zero.

[0006] According to the first aspect, the primary bridge circuit is a primary full-bridge circuit. Adjusting the phase angle of the primary bridge circuit and the secondary bridge circuit includes: adjusting the inner phase shift angle of the primary bridge circuit and adjusting the outer phase shift angle between the primary bridge circuit and the secondary bridge circuit.

[0007] According to the first aspect, or any implementation of the first aspect above, under soft-switching conditions, the inner phase shift angle and the outer phase shift angle are determined by the margin coefficient, the secondary regulation coefficient, the primary voltage and the secondary voltage. The margin coefficient and the secondary regulation coefficient are related to the output current of the inverter circuit. The soft-switching condition is the condition that the turn-off current flowing through the switching device is zero at the turn-off time.

[0008] According to the first aspect, or any implementation of the first aspect above, the margin coefficient is determined by the inner phase shift angle and the outer phase shift angle, wherein the soft switching condition includes the phase of the primary voltage leading the phase of the secondary voltage.

[0009] According to the first aspect, or any implementation of the first aspect above, under soft-switching conditions, the value of the margin coefficient is greater than the limit threshold, and the limit threshold is zero.

[0010] According to the first aspect, or any implementation of the first aspect above, the secondary modulation coefficient is determined by the external phase shift angle, the primary voltage, and the secondary voltage. The soft-switching condition includes the continuous zero-crossing of the coupled inductor current during the switching cycle of the switching device, and the integral of the primary voltage equals the integral of the secondary voltage during the continuous zero-crossing time of the coupled inductor current.

[0011] According to the first aspect, or any implementation of the first aspect above, the value of the secondary modulation coefficient is related to one or more of the following: the circuit design of the secondary bridge circuit; the output voltage of the inverter circuit; and the output current of the inverter circuit.

[0012] According to the first aspect, or any implementation of the first aspect above, the inner phase shift angle and the outer phase shift angle are determined by the output current, primary voltage and secondary voltage of the inverter circuit.

[0013] According to the first aspect, or any implementation of the first aspect above, the margin coefficient is k. b The secondary modulation coefficient is k c ,k b =0.309-0.23*i+0.107*i*i-0.027*i*i*i,k c =―0.0172+1.751*i―1.196*i*i+0.27*i*i*i, where i is the output current of the inverter circuit.

[0014] Secondly, this application provides an inverter circuit, comprising a primary bridge circuit including switching devices; a secondary bridge circuit including switching devices; a coupling inductor connecting the primary and secondary bridge circuits, the coupling inductor including a primary winding and a secondary winding, the primary voltage being the voltage acting on the primary winding and the secondary voltage being the voltage acting on the secondary winding; and a controller connected to the primary and secondary bridge circuits to control the switching devices of the primary and secondary bridge circuits, adjusting the phase angle of the primary and secondary bridge circuits so that the current flowing through the coupling inductor is zero when the switching devices are turned off, wherein when the current of the coupling inductor is zero, the turn-off current flowing through the switching devices is zero.

[0015] Thirdly, this application provides a computer-readable storage medium for computer-executable program code, the program code including a current control method for performing an inverter circuit of the first aspect.

[0016] Fourthly, embodiments of this application provide a computer program that includes commands for executing a current control method in an inverter circuit according to the first aspect.

[0017] The current control method in the inverter circuit proposed in this application adjusts the phase angle of the primary bridge circuit and the secondary bridge circuit so that the current flowing through the coupling inductor is zero when the switching device is turned off, thereby achieving zero-current turn-off of the switching device, avoiding hard turn-off phenomenon, effectively reducing switching losses, and thus significantly improving system efficiency. Attached Figure Description

[0018] Figure 1 This application provides a schematic flowchart of a current control method in an inverter circuit.

[0019] Figure 2 This is a circuit topology diagram of an inverter circuit provided in an embodiment of this application.

[0020] Figure 3 An equivalent circuit topology diagram of an inverter circuit provided in an embodiment of this application.

[0021] Figure 4 This is a circuit modeling diagram provided for an embodiment of this application.

[0022] Figure 5 This is another circuit modeling diagram provided for an embodiment of this application.

[0023] Figure 6 This is a schematic diagram of the fitting curve of the secondary modulation coefficient provided in an embodiment of this application.

[0024] Figure 7 This is a schematic diagram of the fitting curve of a margin coefficient provided in an embodiment of this application.

[0025] Figure 8 This is a schematic diagram illustrating the relationship between turn-off current and time, provided as an embodiment of this application.

[0026] Figure 9 This is a schematic diagram of an inverter circuit provided in an embodiment of this application. Detailed Implementation

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0028] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0029] The terms "first" and "second," etc., used in the specification and claims of this application are used to distinguish different objects, not to describe a specific order of objects. For example, "first target object" and "second target object," etc., are used to distinguish different target objects, not to describe a specific order of target objects.

[0030] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0031] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0032] Currently, inverters are important power conversion devices that convert direct current (DC) to alternating current (AC), and are widely used in various power supply and consumption equipment. The DC side of an inverter can be connected to a DC power source, such as a battery or photovoltaic (PV) system. The AC side can be connected to the consumption equipment or the power grid. In some cases, such as when the inverter is grid-connected and has a battery on the DC side, the DC side can supply power to the AC side, and correspondingly, the AC side can also supply power to the DC side. Grid-connected inverters refer to the inverter being connected to the power grid. When the inverter is not connected to the grid, it can be considered in an off-grid state. In some cases, such as when the inverter is grid-connected, the output voltage of the inverter can be kept consistent with the grid voltage. The power can be controlled by adjusting the output current of the inverter, and the output voltage also changes with the grid voltage.

[0033] Inverters can be categorized into different types depending on their application. For example, a microinverter is a miniature inverter used in photovoltaic (PV) power generation systems, typically with a power output of less than or equal to 1000 watts. In some cases, such as when the inverter's DC side is connected to PV, the initial voltage input on the PV DC side can vary according to the PV's irradiance. However, a module-level maximum power point tracking (MPPT) function is generally configured, meaning the input voltage can also change in real time.

[0034] Based on the design of microinverters, such as in traditional photovoltaic inverter systems, the DC power generated by photovoltaic modules is collected onto a DC bus and then converted into AC power by a centralized inverter. This type of microinverter can be called a DC bus-less microinverter. Among them, the dual active bridge (DAB) microinverter is a type of DC bus-less microinverter, which uses fewer switching devices and possesses the wide-range soft-switching characteristics of DAB circuits. The dual active bridge microinverter can also be called a dual active bridge micro-converter.

[0035] Optimizing inverter efficiency is a core issue in engineering applications. Related technologies can optimize inverter efficiency through methods such as reducing the effective current value, reducing return power, and reducing overall system losses. Reducing the effective current value is a relatively direct approach, but the mathematical model used in this optimization scheme is overly complex and inconvenient for real-time calculation. Optimization schemes based on return power have low efficiency under light loads and limited soft-switching range. Hard turn-off, caused by the switching devices' hard turn-off during inverter operation, leads to overall system losses. Hard turn-off occurs when the switching voltage or current is not zero, resulting in significant energy loss and overall system losses. Soft-switching techniques, including zero-voltage turn-on and zero-current turn-off, can reduce these losses. Zero-voltage turn-on or zero-current turn-off can be achieved when the switching devices are turned off, thereby reducing overall losses caused by the switching devices. Currently, zero-voltage turn-on can be achieved based on different circuit topologies; for example, it can be achieved through parallel parasitic capacitance and inductor resonance. However, while this method reduces the overall losses of the inverter, its implementation requires adjustments to the existing circuit topology and the addition of new electronic components.

[0036] To address the aforementioned issues, this application proposes a current control method for inverter circuits that enables zero-current shutdown without altering the circuit topology. This allows for optimization of inverter efficiency, significant reduction of overall losses, and improved system efficiency.

[0037] The following is combined Figure 1 The embodiments of this application will be described below. Figure 1 This is a flowchart illustrating a current control method in an inverter circuit provided in an embodiment of this application. Figure 1 The inverter circuit may include a primary bridge circuit, a coupling inductor, and a secondary bridge circuit. The primary bridge circuit can be connected to the secondary bridge circuit via a coupling inductor, which may include a primary winding and a secondary winding. For example, the voltage applied to the primary winding may be the primary voltage, and the voltage applied to the secondary winding may be the secondary voltage. Both the primary and secondary bridge circuits may include switching devices.

[0038] In some embodiments, Figure 1 The inverter circuit in the circuit also includes a DC voltage source and an AC voltage source. The primary bridge circuit can be connected to the DC voltage source, and the secondary bridge circuit can be connected to the AC voltage source.

[0039] For example, when Figure 1When the inverter circuit in the circuit is working, it can receive the DC voltage from the DC voltage source through the primary bridge circuit, and change the waveform of the output voltage by changing the conduction and cutoff of the switching devices, thereby converting the DC power into AC power. The AC power is then transmitted to the secondary bridge circuit through the coupling inductor, and the secondary bridge circuit adjusts the waveform of the received AC power, and finally outputs the AC voltage to the AC voltage source.

[0040] Figure 1 The current control method shown may include steps S110 and S120.

[0041] Step S110: Control the switching devices of the primary bridge circuit and the secondary bridge circuit.

[0042] In some embodiments, Figure 1 The inverter circuit may also include a controller, which can be connected to the primary bridge circuit and the secondary bridge circuit. The controller can control the on and off of the switching devices in the primary bridge circuit to control the phase angle of the primary bridge circuit; the controller can also control the on and off of the switching devices in the secondary bridge circuit to control the phase angle of the primary bridge circuit.

[0043] For example, when Figure 1 When the inverter circuit is operating, the controller can control the switching devices of the primary and secondary bridge circuits according to the switching parameters. Optionally, the controller can also perform other steps in this embodiment.

[0044] In some embodiments, the switching devices in the primary-side bridge circuit and the secondary-side bridge circuit may be insulated-gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0045] Step S120: Adjust the phase angle of the primary bridge circuit and the secondary bridge circuit so that the current flowing through the coupling inductor is zero when the switching device is turned off.

[0046] In some embodiments, the controller described above can be used to control the switching device to adjust the phase angle of the primary bridge circuit; control the switching device to adjust the phase angle of the secondary bridge circuit; or control the switching device to adjust the phase angle between the primary bridge circuit and the secondary bridge circuit.

[0047] For example, when the primary-side bridge circuit is a full-bridge circuit, the phase angle of the primary-side bridge circuit may include the inward phase shift angle of the primary-side bridge circuit. The inward phase shift angle refers to the phase difference between the two bridge arms (such as the first bridge arm and the second bridge arm) in the primary-side full-bridge circuit. Optionally, the first bridge arm and the second bridge arm can be considered as half-bridge structures in the primary-side full-bridge circuit, respectively. The half-bridge circuit can be a circuit structure that includes two switching devices.

[0048] For example, when the secondary bridge circuit is a full-bridge circuit, the phase angle of the secondary bridge circuit may include the inner phase shift angle of the secondary bridge circuit.

[0049] For example, the phase angle between the primary bridge circuit and the secondary bridge circuit may include the outward phase shift angle of the primary and secondary bridge circuits. The outward phase shift angle refers to the phase difference between the primary bridge circuit and the secondary bridge circuit. Optionally, the secondary bridge circuit can be a full-bridge circuit or a half-bridge circuit.

[0050] In some embodiments, by adjusting the phase angles of the primary and secondary bridge circuits, the current flowing through the coupling inductor can be made zero at the turn-off moment of the switching device. That is, when the coupling inductor current is zero, the turn-off current flowing through the switching device is zero.

[0051] Figure 2 This is a circuit topology diagram of an inverter circuit provided in an embodiment of this application, wherein L in the inverter circuit 200 m It is a coupled inductor. Figure 2 In the circuit topology diagram shown, S210 can be the primary bridge circuit, which is a full-bridge structure and includes switching devices S1, S2, S3, and S4. S220 is the secondary bridge circuit, which includes switching devices S5, S6, S7, and S8. S230 can be a filter used to filter the signal output by the secondary bridge circuit.

[0052] When inverter circuit 200 starts working, the controller can control switches S1, S2, S3, S4, S5, S6, S7, and S8 to adjust the phase angle of the primary and secondary bridge circuits, thereby adjusting the coupling inductor L. m The current is zero when the coupling inductor L... m When the current is zero, the turn-off current of the switching device is also zero, thus avoiding hard turn-off and significantly reducing overall losses.

[0053] In some embodiments, Figure 2 Equivalent transformations such as Figure 3 The DC voltage source V is described above. dc The primary bridge circuit and the coupled inductor can be equivalent to a DC voltage source.

[0054] The current control method in the inverter circuit proposed in this application adjusts the phase angle of the primary and secondary bridge circuits so that the current flowing through the coupling inductor is zero at the turn-off moment of the switching device, i.e., the turn-off current is also zero. This achieves zero-current turn-off of the switching device, avoids hard turn-off, effectively reduces switching losses, and significantly improves system efficiency. Furthermore, this application does not alter the original circuit topology and does not require the addition of new electronic components, making its implementation more convenient.

[0055] In some embodiments, when the primary bridge circuit is a primary full-bridge circuit, adjusting the phase angle between the primary bridge circuit and the secondary bridge circuit can be done by adjusting the inward phase shift angle of the primary bridge circuit and adjusting the outward phase shift angle between the primary bridge circuit and the secondary bridge circuit.

[0056] In some embodiments, the secondary bridge circuit can be a full-bridge structure or a half-bridge structure.

[0057] In some embodiments, by adjusting the inner phase shift angle of the primary-side full-bridge circuit and the outer phase shift angle of the primary-side bridge circuit, the coupling current can be made zero, and the turn-off current of the switching devices can be made zero, thereby avoiding hard turn-off and significantly reducing overall losses.

[0058] For example, when the switching device is turned off, the turn-off current flowing through the switching device in the inverter circuit is zero, that is, the current flowing through the coupling inductor in the inverter circuit is zero. Figure 4 For example, Figure 4 It can be based on Figure 2 The circuit model diagram generated from the circuit topology diagram. Figure 4 The top image shows the model of the inductor current, with the horizontal axis representing time and the vertical axis representing the current value of the coupled inductor. The bottom image shows the primary voltage V. p and secondary voltage V s The model diagram shows the time on the horizontal axis and the voltage amplitude on the vertical axis.

[0059] exist Figure 4 In this context, times t1 and t2 can be considered as the moments within a switching cycle when the coupled inductor current continuously crosses zero. At time t1, the primary voltage V... p Leading secondary voltage V s It is understandable that the primary voltage V can be adjusted by changing the inner phase shift angle of the primary-side full-bridge circuit and the outer phase shift angle of the primary-side bridge circuit. p Leading secondary voltage V sThis ensures that the current flowing through the coupling inductor is zero when the switching device is turned off, and consequently, the turn-off current flowing through the switching device in the inverter circuit is also zero. It should be understood that in the inverter circuit of this embodiment, a switching cycle refers to the time interval from the start of one switching action to the start of the next identical switching action.

[0060] Again Figure 5 For example, Figure 5 Also based on Figure 2 The circuit model diagram generated from the circuit topology diagram.

[0061] exist Figure 5 In the circuit model diagram S510, the vertical axis is V. p The voltage value, V p The x-axis represents the primary voltage, and the y-axis represents the time variable. The circuit model diagram is S520, with the y-axis representing V. s The voltage value, V s The horizontal axis represents the secondary voltage, and the vertical axis represents the time variable. The circuit model diagram S530 shows the current value of iL on the vertical axis, where iL is the current value of the coupled inductor, and the horizontal axis represents the time variable. D1 is the inner phase shift angle of the primary-side full-bridge circuit, and D2 is the outer phase shift angle of the primary and secondary-side bridge circuits.

[0062] As can be seen from circuit model diagrams S510 and S520, the primary voltage V p Leading secondary voltage V s As can be seen from the circuit model diagram S530, the coupling inductor current is related to the primary voltage V. p Leading secondary voltage V s During the time period t1, the coupled inductor current is negative, reaching zero at time t1, and then becomes positive and continuously increases. It is understandable that the primary voltage V can be adjusted by changing the inner phase shift angle D1 and the outer phase shift angle D2 of the primary-side full-bridge circuit. p Leading secondary voltage V s This ensures that the current flowing through the coupling inductor is zero when the switching device is turned off, and the turn-off current flowing through the switching device of the inverter circuit is also zero at this time, thus avoiding hard turn-off.

[0063] In some embodiments, under soft-switching conditions, the inner and outer phase shift angles can be determined by the margin factor, the secondary modulation factor, the primary voltage, and the secondary voltage.

[0064] In some embodiments, the margin factor can be considered as a safety margin introduced to ensure stable operation of the system under operating conditions. Exemplarily, the margin factor can compensate for changes in system parameters, the influence of environmental conditions, and uncertainties in the design. Optionally, the value of the margin factor can be related to the primary and secondary bridge circuits. Optionally, the value of the margin factor can be related to the output current of the inverter circuit.

[0065] In some embodiments, the secondary modulation factor can be considered a factor related to the secondary bridge circuit. For example, the value of the secondary modulation factor can be related to the circuit design of the secondary bridge circuit. Alternatively, the secondary modulation factor can also be considered a factor related to the inverter circuit; for example, the secondary modulation factor can be related to the output voltage or the output current of the inverter circuit.

[0066] In some embodiments, the soft-switching condition is the condition that, at the turn-off moment, the turn-off current flowing through the switching device is zero. Alternatively, the soft-switching condition can be understood as ensuring that, in the inverter circuit, at the turn-off moment, the current flowing through the coupling inductor is zero.

[0067] For example, the soft-switching condition may include the phase of the primary voltage leading the phase of the secondary voltage. In some embodiments, when the phase of the primary voltage leads the phase of the secondary voltage, the margin factor may be determined by the inner phase shift angle and the outer phase shift angle.

[0068] For example, the soft-switching condition may include the coupled inductor current continuously crossing zero during the switching cycle of the switching device, assuming the zero-crossing times are t1 and t2. Then, during the time intervals t1 and t2, the integral of the primary voltage is equal to the integral of the secondary voltage. It should be understood that in this application, the discussion is based on one switching cycle. In some embodiments, when the coupled inductor current continuously crosses zero at times t1 and t2 within one switching cycle, and the integrals of the voltages acting on the coupled inductor at times t1 and t2 are equal, the secondary modulation coefficient can be determined by the external phase shift angle, the primary voltage, and the secondary voltage.

[0069] In some embodiments, under soft-switching conditions, the margin factor k b The value is greater than the limit threshold, so that after introducing the margin coefficient, the system can be guaranteed to operate stably under various operating conditions. Optionally, the limit threshold can be zero.

[0070] by Figure 4 , Figure 5 Taking an example, we will continue to describe the embodiments of this application.

[0071] Figure 5 In the circuit model diagram S510, the vertical axis is V. p The voltage value, V pThe x-axis represents the primary voltage, and the y-axis represents the time variable. The y-axis of the S520 circuit model diagram represents V. s The voltage value, V s The horizontal axis represents the secondary voltage, and the vertical axis represents the time variable. In the circuit model diagram S530, the vertical axis represents the current value of iL, where iL is the current value of the coupled inductor, and the horizontal axis represents the time variable. D1 is the inner phase shift angle of the primary-side full-bridge circuit, and D2 is the outer phase shift angle of the primary and secondary-side bridge circuits.

[0072] Figure 5 One of the waveform periods is a switching period T, V s and V p The change period is the same, which can also be understood as V s and V p The switching cycles are the same. If we only consider one switching cycle, then V s and V p The difference at the highest phase is 2πD², therefore it can be deduced that V s and V p If the difference at the zero point is 2πD2, then when establishing a coordinate system with Y = -πD1, V p The zero-crossing point is 2πD1, V s The zero-crossing point is π*D1+2*π*D2, t1 is π*D1+2*π*D2, and t2 is π*D1+2*π*D2+π. In the time domain, this is expressed as:

[0073] After obtaining the time-domain expressions for t1 and t2, integrating the primary and secondary voltages at times t1 and t2, we obtain the following expression: f refers to the switching frequency, such as a frequency converter between 50kHz and 200kHz. Where k... c k is the secondary modulation coefficient. c It can be related to the circuit design of the secondary bridge circuit.

[0074] Under the condition of ensuring soft switching, within one switching cycle, the integral of the voltage across the coupled inductor is equal during the consecutive zero-crossing moments of the current flowing through the coupled inductor at the turn-off moment. Therefore, the expression can be obtained: Combined expression: Formula 1 can be obtained: (1-4D2)V p =k c V s .

[0075] To ensure soft switching, the phase of the primary voltage leads the phase of the secondary voltage. In some embodiments, to ensure the phase of the primary voltage leads the phase of the secondary voltage, and that D1 and D2 have solutions, then from... Figure 5 From this, we can obtain:

[0076] Here, a margin coefficient k can be introduced. b Formula 2 is obtained:

[0077] It is understandable that 0 in Formula 2 represents a limiting threshold, and under soft-switching conditions, the margin coefficient k b The value is greater than the limit threshold so that after introducing the margin coefficient, the system can be guaranteed to operate stably under various operating conditions.

[0078] Substituting the formula into Formula 2, we can obtain the expressions for the inner phase shift angle D1 and the outer phase shift angle D2:

[0079] Therefore, from the above expression, it can be seen that, under the condition of ensuring soft switching, the inner phase shift angle D1 and the outer phase shift angle D2 can be determined by the margin coefficient k. b Secondary modulation coefficient k c Primary voltage V p and secondary voltage V s Sure.

[0080] It is understandable that the inner phase shift angle D1 and the outer phase shift angle D2 are related to the margin coefficient k. b Secondary modulation coefficient k c Primary voltage V p and secondary voltage V s Under the premise of conforming to the established expression model, it can be ensured that the soft switching condition is realized, that is, the turn-off current flowing through the switching device is zero at the turn-off time, thus avoiding the hard turn-off phenomenon and reducing the power consumption of the whole machine.

[0081] In some embodiments, the margin factor and the secondary regulation factor can be determined by the output current of the inverter circuit. Optionally, when the margin factor and the secondary regulation factor are determined by the output current of the inverter circuit, the inner phase shift angle and the outer phase shift angle can be determined by the output current, primary voltage, and secondary voltage of the inverter circuit.

[0082] For example, a fitting model for the margin coefficient and the secondary regulation coefficient can be constructed under soft-switching conditions. During the model fitting process, the output current of the inverter circuit is adjusted to generate fitting expressions for the margin coefficient and the secondary regulation coefficient. Optionally, the margin coefficient can be k. b The secondary coefficient can be k c Then k b and k c It can be expressed using the output current i, and the specific expression is: k b=0.309-0.23*i+0.107*i*i-0.027*i*i*i,k c =0.0172+1.751*i―1.196*i*i+0.27*i*i*i.

[0083] In some embodiments, based on Figure 2 The circuit topology of the inverter circuit can be used to construct fitting models for the margin coefficient and secondary regulation coefficient under soft-switching conditions. During the fitting process, by fixing the output current of the inverter circuit and adjusting the output voltage, different output powers can be obtained, thus yielding fitting curves for the margin coefficient and secondary regulation coefficient, as shown below. Figure 6 , Figure 7 As shown.

[0084] For example, when the inverter circuit is in grid-connected mode, this fitting model, under soft-switching conditions, can fix the value of the inverter circuit's output current i, and, combined with Formula 1 above, generate the secondary modulation coefficient k. c The fitted curve.

[0085] The fitting model can fix the output current i at 4A. Taking a single-phase AC voltage of 220V as an example, the output power of the inverter circuit can be continuously changed by adjusting the output voltage from 0V to 220V. This is combined with Formula 1: (1-4D²)V p =k c V s Under soft-switching conditions, adjusting D2 yields k. c The fitted curve, such as Figure 6 k in c1 When the voltage is adjusted to 220V, the first round of fitting simulation test can be considered complete.

[0086] The fitting model can fix the output current i at 2A, and then adjust the output voltage from 0V to 220V. Under soft-switching conditions, D2 is adjusted to obtain k. c2 The fitting model can keep the output current i fixed at 1A, adjust the output voltage from 0V to 220V, and under soft-switching conditions, adjust D2 to obtain k. c3 .

[0087] For example, when the inverter circuit is in grid-connected mode, this fitting model, under soft-switching conditions, can fix the value of the inverter circuit's output current i, and, combined with Formula 2 above, generate the margin coefficient k. b The fitted curve.

[0088] The fitting model can fix the output current i at 4A. Taking a single-phase AC voltage of 220V as an example, the output power of the inverter circuit is continuously changed by adjusting the output voltage from 0V to 220V. This is combined with Formula 2: Under soft-switching conditions, D1 and D2 can be adjusted to obtain k. b The fitted curve, such as Figure 7 k in b1 When the voltage was adjusted to 220V, the first round of fitting simulation test ended.

[0089] The fitting model can fix the output current i at 2A, and then adjust the output voltage from 0V to 220V. Under soft-switching conditions, D1 and D2 are adjusted to obtain k. b2 The fitting model can keep the output current i fixed at 1A, adjust the output voltage from 0V to 220V, and under soft-switching conditions, adjust D1 and D2 to obtain k. b3 .

[0090] By using the constructor method, targeting Figure 6 and Figure 7 From the fitted curve, the margin coefficient k can be obtained. b and secondary modulation coefficient k c The expression is: k c =―0.0172+1.751*i―1.196*i*i+0.27*i*i*i,k b =0.309-0.23*i+0.107*i*i-0.027*i*i*i.

[0091] Alternatively, k can also be... c and k b Substituting the expression into the expressions for the inner phase shift angle D1 and the outer phase shift angle D2, the expressions for the inner phase shift angle D1 and the outer phase shift angle D2 are: k c and k b Substituting the expressions into the given expressions, we can obtain the new expressions for D1 and D2 as follows:

[0092]

[0093] As can be seen from the above, the inner phase shift angle D1 of the primary bridge circuit and the outer phase shift angle D2 of the primary and secondary bridge circuits can be determined by the inverter circuit's output current i and primary voltage V. p and secondary voltage V s Determined. When the inner phase shift angle D1 and the outer phase shift angle D2 are related to the inverter circuit's output current i and primary voltage V... p and secondary voltage V sWhen the above expression is satisfied, it can be ensured that the turn-off current of the switching devices in the inverter circuit is zero, avoiding hard turn-off and thus reducing the functional loss of the system.

[0094] In the embodiments of this application, the primary bridge circuit of the inverter circuit can be connected to a DC voltage source, and the secondary bridge circuit can be connected to an AC voltage source. Based on this fitting model, during the operation of the inverter circuit, the primary voltage V p Secondary voltage V s Both the output current i and the voltage i are changing, but at each moment, there will be a corresponding primary voltage V. p Secondary voltage V s The values ​​of the output current i are obtained so that at any given moment, the inner phase shift angle D1 of the primary bridge circuit and the outer phase shift angle D2 of the primary and secondary bridge circuits can be obtained to make the turn-off current zero, thereby reducing the system power consumption.

[0095] In some embodiments, due to partial losses caused by circuit connections, it may be impossible to consistently ensure that the turn-off current is zero. Therefore, the soft-switching condition can also be the condition that the turn-off current flowing through the switching device tends to zero at the turn-off moment. For example, the value of the turn-off current AC_cut of the primary bridge circuit can be set to (0, 0.6), and the value of the turn-off current AC_cut of the secondary bridge circuit can be set to (-0.6, 0). During the fitting process of the above-mentioned margin coefficient and secondary modulation coefficient fitting model, k is continuously adjusted. b and k c The value of is adjusted so that the turn-off current meets the soft-switching condition, while the operating condition record k is changed. b and k c The value of is determined, and a curve is fitted.

[0096] Figure 8 Based on Figure 2 The diagram shows the relationship between the turn-off current AC_cut of the primary bridge circuit and time when the inverter circuit topology is working, as well as the relationship between the turn-off current AC_cut of the secondary bridge circuit and time.

[0097] from Figure 8 As can be seen, under the premise of satisfying the new expressions D1 and D2, the turn-off current of the switching device is almost zero, thus achieving a significant reduction in turn-off current. Taking a power grid frequency of 50Hz as an example, one power frequency cycle is 0.02 seconds (s), which is 20 milliseconds (ms). In 1.5 power frequency cycles, such as Figure 8 Between 10ms and 40ms, the turn-off current of both the primary bridge circuit and the secondary bridge circuit approaches zero, thereby reducing overall losses and improving system efficiency.

[0098] The method embodiments of this application have been described in detail above. Based on the above, this application also proposes an inverter circuit, which will be discussed below in conjunction with... Figure 9 The circuit embodiments of this application are described in detail below. It should be understood that the descriptions of the above method embodiments correspond to the descriptions of the circuit embodiments; therefore, any parts not described in detail can be referred to the foregoing method embodiments.

[0099] Figure 9 This is a schematic diagram of an inverter circuit 900 provided in an embodiment of this application. The inverter circuit 900 may include:

[0100] The primary-side bridge circuit S910 includes switching devices.

[0101] The secondary bridge circuit S930 includes switching devices.

[0102] The coupling inductor S920 connects the primary bridge circuit S910 and the secondary bridge circuit S930. The coupling inductor S920 may include a primary winding and a secondary winding. The primary voltage is the voltage acting on the primary winding, and the secondary voltage is the voltage acting on the secondary winding.

[0103] The controller S940 is connected to the primary bridge circuit S910 and the secondary bridge circuit S930 to control the switching devices of the primary bridge circuit S910 and the secondary bridge circuit S930, and adjust the phase angle of the primary bridge circuit S910 and the secondary bridge circuit S930 so that the current through the coupling inductor S920 is zero. When the current through the coupling inductor S920 is zero, the turn-off current of the switching device is zero.

[0104] In some embodiments, the inverter circuit 900 includes a DC voltage source S950 and an AC voltage source S960.

[0105] In some embodiments, the secondary bridge circuit S930 can be a full-bridge structure or a half-bridge structure.

[0106] In some embodiments, when the primary bridge circuit S910 is a primary full-bridge circuit, the controller S940 can control the switching devices of the primary bridge circuit S910 and the secondary bridge circuit S930, adjust the inner phase shift angle of the primary bridge circuit S910, and adjust the outer phase shift angle between the primary bridge circuit S910 and the secondary bridge circuit S930.

[0107] In some embodiments, under soft-switching conditions, the inner and outer phase shift angles can be determined by the margin coefficient, the secondary regulation coefficient, the primary voltage, and the secondary voltage. The margin coefficient and the secondary regulation coefficient can be related to the output current of the inverter circuit. The soft-switching condition can be the condition that the turn-off current flowing through the switching device is zero at the turn-off time.

[0108] In some embodiments, the margin factor can be determined by the inner phase shift angle and the outer phase shift angle, wherein the soft-switching condition includes the phase of the primary voltage leading the phase of the secondary voltage.

[0109] In some embodiments, under soft-switching conditions, the margin coefficient is greater than the limit threshold, which is zero.

[0110] In some embodiments, the secondary modulation coefficient is determined by the outward phase shift angle, the primary voltage, and the secondary voltage. The soft-switching condition includes the continuous zero-crossing of the coupled inductor current during the switching cycle of the switching device, and the integral of the primary voltage equals the integral of the secondary voltage during the continuous zero-crossing time of the coupled inductor current.

[0111] In some embodiments, the value of the secondary modulation coefficient may be related to one or more of the following: the circuit design of the secondary bridge circuit; the output voltage of the inverter circuit; and the output current of the inverter circuit.

[0112] In some embodiments, the inner phase shift angle and the outer phase shift angle can be determined by the output current, primary voltage, and secondary voltage of the inverter circuit.

[0113] In some embodiments, the margin factor is k b The secondary modulation coefficient is k c ,k b =0.309-0.23*i+0.107*i*i-0.027*i*i*i,k c =―0.0172+1.751*i―1.196*i*i+0.27*i*i*i, where i is the output current of the inverter circuit.

[0114] Furthermore, this application also proposes a computer-readable storage medium storing a computer program. When the computer program is executed by a computer, it implements the operation of the current control method in the inverter circuit provided in the above embodiments. The specific steps will not be described in detail here.

[0115] This application also proposes a computer program that includes commands for executing the current control method in the inverter circuit provided in the above embodiments.

[0116] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity / operation / object from another, and do not necessarily require or imply any such actual relationship or order between these entities / operations / objects; the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0117] For the device embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and relevant details can be found in the description of the method embodiments. The device embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separate. Some or all of the modules can be selected according to actual needs to achieve the purpose of this application. Those skilled in the art can understand and implement this without creative effort.

[0118] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0119] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, television, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0120] The above are merely embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A current control method in an inverter circuit, characterized by, The inverter circuit comprises a primary side bridge circuit, a coupling inductor and a secondary side bridge circuit, the primary side bridge circuit connects the secondary side bridge circuit through the coupling inductor, the coupling inductor comprises a primary side winding and a secondary side winding, a voltage acting on the primary side winding is a primary side voltage, a voltage acting on the secondary side winding is a secondary side voltage, the primary side bridge circuit and the secondary side bridge circuit each comprise a switching device, and the current control method comprises: controlling the switching device of the primary side bridge circuit and the switching device of the secondary side bridge circuit; adjusting phase angles of the primary side bridge circuit and the secondary side bridge circuit, so that a current flowing through the coupling inductor is zero at a turn-off time of the switching device, wherein, when the current flowing through the coupling inductor is zero, a turn-off current flowing through the switching device is zero.

2. The method of claim 1, wherein, The primary side bridge circuit is a primary side full-bridge circuit, and the adjusting of the phase angles of the primary side bridge circuit and the secondary side bridge circuit comprises: adjusting an inner phase shift angle of the primary side bridge circuit, and adjusting an outer phase shift angle between the primary side bridge circuit and the secondary side bridge circuit.

3. The method of claim 2, wherein: under a soft switching condition, the inner phase shift angle and the outer phase shift angle are determined by a margin coefficient, a secondary modulation coefficient, the primary side voltage and the secondary side voltage, the margin coefficient and the secondary modulation coefficient are related to an output current of the inverter circuit, and the soft switching condition is a condition that the turn-off current flowing through the switching device is zero at the turn-off time of the switching device.

4. The method of claim 3, wherein: the margin coefficient is determined by the inner phase shift angle and the outer phase shift angle, and wherein the soft switching condition comprises that a phase of the primary side voltage leads a phase of the secondary side voltage.

5. The method of claim 4, wherein: under the soft switching condition, a value of the margin coefficient is greater than a limit threshold, and the limit threshold is zero.

6. The method of claim 3, wherein: the secondary modulation coefficient is determined by the outer phase shift angle, the primary side voltage and the secondary side voltage, and wherein the soft switching condition comprises that the current flowing through the coupling inductor continuously crosses zero within a switching period of the switching device, and that an integral of the primary side voltage is equal to an integral of the secondary side voltage within a time when the current flowing through the coupling inductor continuously crosses zero.

7. The method of claim 3, wherein: a value of the secondary modulation coefficient is related to one or more of the following: a circuit design of the secondary side bridge circuit; an output voltage of the inverter circuit; an output current of the inverter circuit.

8. The method of claim 3, wherein: the inner phase shift angle and the outer phase shift angle are determined by an output current of the inverter circuit, the primary side voltage and the secondary side voltage.

9. The method of claim 3, wherein, The margin coefficient is k b , the secondary regulation coefficient is k c , k b = 0.309 - 0.23*i + 0.107*i*i - 0.027*i*i*i, k c = -0.0172 + 1.751*i - 1.196*i*i + 0.27*i*i*i, where i is the output current of the inverter circuit.

10. An inverter circuit, characterized by comprising: comprise: a primary side bridge circuit comprising a switching device; a secondary side bridge circuit comprising the switching device; a coupling inductor connecting the primary bridge circuit and the secondary bridge circuit, the coupling inductor comprising a primary winding and a secondary winding, a primary voltage being a voltage acting on the primary winding, a secondary voltage being a voltage acting on the secondary winding; a controller connected to the primary bridge circuit and the secondary bridge circuit to control the switching devices of the primary bridge circuit and the switching devices of the secondary bridge circuit, to adjust phase angles of the primary bridge circuit and the secondary bridge circuit so that a current flowing through the coupling inductor is zero at a turn-off time of a switching device, wherein a turn-off current flowing through the switching device is zero when the current flowing through the coupling inductor is zero.

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