An ac-dc power converter control method and storage medium

Abstract

This application proposes a control method and storage medium for an AC / DC power converter. By acquiring the required output current and input voltage, and based on the transformer circuit, the inner phase shift angle of the DC-side bridge arm or AC-side bridge arm is calculated. The inner phase shift angle includes the inner phase shift angle of the DC-side bridge arm or the inner phase shift angle of the AC-side bridge arm. Based on the inner phase shift angle, the operating frequency of the transformer circuit is determined to linearize the function of the output current with respect to the phase shift angle variable. Based on the inner phase shift angle and the operating frequency, control logic for the switching components in the DC-side bridge arm or AC-side bridge arm is generated. Sinusoidal trajectory tracking can be achieved using simple closed-loop control. The proposed phase shift angle and switching frequency can be obtained analytically, are simple to calculate and easy to implement, achieving zero-voltage turn-on and high-efficiency operation, thereby improving the user experience.

Description

Technical Field

[0001] This application relates to the field of circuit control technology, specifically to an AC / DC power converter control method and storage medium. Background Technology

[0002] Bidirectional AC / DC converters are a key technology in fields such as new energy, microgrids, and electric vehicle charging. Currently, these converters mainly have two topologies: the two-stage topology, which is the mainstream solution for current on-board chargers, consists of a front-end PWM rectifier and a rear-end dual active bridge (DAB) or resonant converter connected in series. Its main advantages are mature technology, stable structure, and reliable control. The single-stage topology, unlike the two-stage topology, directly performs power conversion. The potential advantages of this design are higher efficiency, power density, and lower cost.

[0003] In conceiving and implementing this application, the inventors discovered at least the following problems: existing bidirectional power converter topologies often require complex control algorithms, resulting in low control efficiency and a poor user experience. The foregoing description is intended to provide general background information and does not necessarily constitute prior art. Summary of the Invention

[0004] To alleviate the aforementioned technical problems, this application provides an AC / DC power converter control method. The AC / DC power converter includes a DC-side bridge arm, a transformer circuit, and an AC-side bridge arm connected in sequence. The AC / DC power converter control method includes: Obtain the required output current and input voltage, and calculate the inner phase shift angle of the DC side bridge arm or the AC measuring bridge arm according to the transformer circuit; the inner phase shift angle includes the inner phase shift angle of the DC side bridge arm or the inner phase shift angle of the AC measuring bridge arm; Based on the inner phase shift angle, the operating frequency of the transformer circuit is determined so that the output current is linearized as a function of the phase shift angle variable; Based on the internal phase shift angle and the operating frequency, control logic for the switching components in the DC-side bridge arm or AC-side bridge arm is generated.

[0005] Optionally, the process of obtaining the required output current and input voltage, and calculating the inner phase shift angle of the DC-side bridge arm or AC-side bridge arm based on the transformer circuit, includes: Obtain the number of turns in the transformer circuit to determine the leakage inductance and maximum switching frequency of the power converter; Based on the leakage inductance and maximum switching frequency, the required output current and input voltage are combined to calculate the inner phase shift angle.

[0006] Optionally, the difference between the inner phase shift angle of the DC-side bridge arm and the inner phase shift angle of the AC-side bridge arm is taken as the outer phase shift angle; the process of calculating the inner phase shift angle based on the leakage inductance and the maximum switching frequency, and by integrating the required output current and input voltage, includes: Based on the inner phase shift angle, the input voltage, and the outer phase shift angle between the DC side bridge arm and the AC measuring bridge arm, the nodes of the secondary bridge arm are selected as ports for output current analysis to obtain multiple current change points during the operation of the secondary bridge arm. The multiple current change points are connected sequentially by straight line segments in chronological order to determine the linear equations of the multiple line segments respectively. Based on multiple linear equations and the leakage inductance and maximum switching frequency, the average current expression of the secondary bridge arm output is obtained. Obtain the phase shift ratio of the outer phase shift angle to the inner phase shift angle, and calculate the inner phase shift angle based on the average current expression and the required output current.

[0007] Optionally, the switching device in the DC-side bridge arm and / or the AC-side bridge arm is a MOSFET, and the process of obtaining the phase shift angle ratio of the outer phase shift angle to the inner phase shift angle includes: Based on the current analysis of the multiple current change points, a first constraint condition is established for the phase shift angle ratio, so that when the current of each switch in the AC / DC power converter maintains its original direction (body diode is conducting), the corresponding switch is turned on, thereby determining the first value range of the phase shift angle ratio. Based on the reactive power analysis during the operation of the AC / DC power converter, a second constraint condition is established for the phase shift angle ratio to minimize the total energy of the reverse return flow in each oscillation cycle of the AC / DC power converter, thereby determining the second value range of the phase shift angle ratio. The phase shift angle ratio is determined based on the first value range and the second value range.

[0008] Optionally, determining the operating frequency of the transformer circuit based on the inner phase shift angle, so as to linearize the output current as a function of the phase shift angle variable, includes: Based on the phase shift angle ratio and the inner phase shift angle, a switching frequency function is constructed; The operating frequency of the transformer circuit is calculated based on the switching frequency function, so as to linearize the relationship between the output current and the phase shift angle variable using frequency conversion control.

[0009] Optionally, the AC / DC power converter includes a DC-side bridge arm, a transformer circuit, and an AC measuring bridge arm connected in sequence, wherein: The DC side bridge arm includes a first bridge arm and a second bridge arm, and the AC side bridge arm includes a first directional switch unit, a second directional switch unit, a first capacitor and a second capacitor; The first end of the first bridge arm and the first end of the second bridge arm are connected to the positive terminal of the DC bus, the second end of the first bridge arm and the second end of the second bridge arm are connected to the negative terminal of the DC bus, the switch selection terminal of the first bridge arm is connected to the first terminal of the DC side of the transformer circuit, and the switch selection terminal of the second bridge arm is connected to the second terminal of the DC side of the transformer circuit. The first end of the first directional switch unit is connected to the live wire end of the AC bus, the second end of the first directional switch unit is connected to the second end of the second directional switch unit and the first end of the AC side of the transformer circuit, and the first end of the second directional switch unit is connected to the neutral wire end of the AC bus. The first terminal of the first capacitor is connected to the first terminal of the first directional switch unit, the second terminal of the first capacitor is connected to the second terminal of the second capacitor, the first terminal of the second capacitor is connected to the first terminal of the second directional switch unit, and the second terminal of the AC side of the transformer circuit is connected to the common terminal of the first capacitor and the second capacitor.

[0010] Optionally, the first directional switching unit includes a fifth switching element, a sixth switching element, a first diode, and a second diode D2; The first end of the fifth switching element is connected to the first end of the first directional switching unit, the second end of the fifth switching element is connected to the anode of the first diode, and the cathode of the first diode is connected to the second end of the first directional switching unit. The first end of the sixth switching element is connected to the second end of the first directional switching unit, the second end of the sixth switching element is connected to the anode of the second diode D2, and the cathode of the second diode D2 is connected to the first end of the first directional switching unit.

[0011] Optionally, the second directional switch unit includes a seventh switch element and an eighth switch element, the first end of the seventh switch element is connected to the first end of the second directional switch, the second end of the seventh switch element is connected to the first end of the eighth switch element, and the second end of the eighth switch element is connected to the second end of the second directional switch unit.

[0012] Optionally, the first bridge arm includes a first switch and a second switch, and the second bridge arm includes a third switch and a fourth switch. The first end of the first switch is connected to the positive terminal of the DC bus; the first end of the second switch is connected to the second end of the first switch; and the second end of the second switch is connected to the negative terminal of the DC bus. The first end of the third switch is connected to the positive terminal of the DC bus; and the first end of the fourth switch is connected to the second end of the third switch; and the second end of the fourth switch is connected to the negative terminal of the DC bus. The first end of the DC side of the transformer circuit is connected to the common terminal of the first switch and the second switch, and the second end of the DC side of the transformer circuit is connected to the common terminal of the third switch and the fourth switch.

[0013] Optionally, the AC / DC power converter operates during the DC-to-AC conversion process, and the process of generating control logic for the switching elements in the DC-side bridge arm or AC-side bridge arm based on the inner phase shift angle and the operating frequency includes: During the positive half-cycle of the AC bus, the sixth and eighth switches are controlled to be normally on, and the fifth and seventh switches are controlled to operate in a high-frequency complementary switching state.

[0014] Optionally, the process of controlling the sixth and eighth switches to be normally on and controlling the fifth and seventh switches to operate in a high-frequency complementary switching state further includes: From the first moment to the second moment, control the first and fourth switches to be turned on, control the second and third switches to be turned off, control the seventh switch to be turned on, and control the fifth switch to be turned off; From the second time point to the third time point, the first and fourth switches are turned on, the second and third switches are turned off, the fifth switch is turned on, and the seventh switch is turned off. From the third to the fourth moment, the second and fourth switches are turned on, the first and third switches are turned off, the fifth switch is turned on, and the seventh switch is turned off. From the fourth moment to the fifth moment, control the first switch and the fourth switch to be turned on, control the second switch and the third switch to be turned off, control the fifth switch to be turned on, and control the seventh switch to be turned off; From the fifth moment to the sixth moment, control the second and third switches to be turned on, control the first and fourth switches to be turned off, control the seventh switch to be turned on, and control the fifth switch to be turned off; From the sixth to the seventh moment, the second and fourth switches are turned on, the first and third switches are turned off, the seventh switch is turned on, and the fifth switch is turned off.

[0015] This application also provides a storage medium storing a computer program, which, when executed by a processor, implements the steps of the AC / DC power converter control method described above.

[0016] The AC / DC power converter control method and storage medium provided in this application obtain the required output current and input voltage, and calculate the inner phase shift angle of the DC-side bridge arm or AC-side bridge arm according to the transformer circuit. The inner phase shift angle includes the inner phase shift angle of the DC-side bridge arm or the inner phase shift angle of the AC-side bridge arm. Based on the inner phase shift angle, the operating frequency of the transformer circuit is determined to linearize the function of the output current and the phase shift angle variable. Based on the inner phase shift angle and the operating frequency, the control logic of the switching components in the DC-side bridge arm or AC-side bridge arm is generated. The nonlinear function of the phase shift angle can be linearized using a frequency conversion control algorithm, so that sinusoidal trajectory tracking can be achieved with simple closed-loop control. The proposed modulation strategy minimizes reactive power during the switching cycle, significantly reduces current stress and power loss, and thus achieves high-efficiency operation. The proposed phase shift angle and switching frequency can be obtained in analytical form, which is simple to calculate and easy to implement, thereby improving the user experience. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0018] Figure 1 This is a flowchart of an AC / DC power converter control method according to an embodiment of this application.

[0019] Figure 2 This is a schematic diagram of an AC / DC power converter topology according to an embodiment of this application.

[0020] Figure 3 This is a schematic diagram of an AC / DC power converter circuit according to an embodiment of this application.

[0021] Figure 4 This is a timing diagram of the operation of an AC / DC power converter according to an embodiment of this application.

[0022] Figure 5 This is a schematic diagram of the control logic of an embodiment of this application.

[0023] Figure 6This is a schematic diagram of the operating timing of an AC / DC power converter according to an embodiment of this application.

[0024] Figure 7 This is a schematic diagram illustrating the linearization of the output current and control variables according to an embodiment of this application.

[0025] Figure 8 This is a schematic diagram of the waveform generated during simulation verification of an embodiment of this application.

[0026] Figure 9 This is a schematic diagram showing the timing details of a bridge arm switch according to an embodiment of this application.

[0027] Figure 10 This is a schematic diagram of the voltage and current across a transformer according to an embodiment of this application.

[0028] Figure 11 This is a schematic diagram of the voltage across an inductor according to an embodiment of this application.

[0029] The realization of the objectives, functional features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and textual descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concepts of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0030] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0031] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus 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 apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, components, features, and elements with the same names in different embodiments of this application may have the same meaning or different meanings, the specific meaning of which must be determined by its interpretation in that specific embodiment or further in conjunction with the context of that specific embodiment.

[0032] It should be understood that although the terms first, second, third, etc., may be used herein to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this document, a first motor may also be referred to as a second motor, and similarly, a second motor may also be referred to as a first motor. Depending on the context, the word "if," as used herein, can be interpreted as "when," "when," or "in response to determination." Furthermore, as used herein, the singular forms "a," "an," and "the" are intended to also include the plural forms unless the context indicates otherwise. It should be further understood that the terms "comprising," "including," indicate the presence of the stated feature, step, operation, element, component, item, kind, and / or group, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups. The terms "or," "and / or," "including at least one of the following," etc., as used in this application, can be interpreted as inclusive, or mean any one or any combination thereof. For example, "including at least one of the following: A, B, C" means "any one of the following: A; B; C; A and B; A and C; B and C; A and B and C." Similarly, "A, B, or C" or "A, B, and / or C" means "any one of the following: A; B; C; A and B; A and C; B and C; A and B and C." Exceptions to this definition only occur when the combination of elements, functions, steps, or operations is inherently mutually exclusive in some way.

[0033] It should be understood that although the steps in the flowcharts of this application's embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps.

[0034] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”

[0035] It should be noted that step designations such as S10 and S20 are used in this document for the purpose of more clearly and concisely describing the corresponding content, and do not constitute a substantial limitation on the order. In specific implementation, those skilled in the art may execute S20 first and then S10, etc., but these should all be within the protection scope of this application.

[0036] First Embodiment This application provides a control method for an AC / DC power converter. Figure 1 This is a flowchart of an AC / DC power converter control method according to an embodiment of this application.

[0037] like Figure 1 As shown, in one embodiment, the AC / DC power converter includes a DC-side bridge arm, a transformer circuit, and an AC-side bridge arm connected in sequence. The AC / DC power converter control method includes: S10: Obtain the required output current and input voltage, and calculate the inner phase shift angle of the DC side bridge arm or the AC measuring bridge arm according to the transformer circuit; the inner phase shift angle includes the inner phase shift angle of the DC side bridge arm or the inner phase shift angle of the AC measuring bridge arm; S20: Determine the operating frequency of the transformer circuit based on the inner phase shift angle, so as to linearize the function of the output current and the phase shift angle variable; S30: Based on the inner phase shift angle and the operating frequency, generate the control logic for the switching components in the DC side bridge arm or AC side bridge arm.

[0038] A power converter is an electronic device that can convert one type of current into another, including both DC and AC power conversion. For example, a bidirectional AC / DC converter, as a power electronic device capable of bidirectional conversion between AC and DC, involves multiple key components and complex control strategies in its operation. A transformer is a device that uses the principle of electromagnetic induction to change AC voltage. Depending on the number of turns on the source and secondary sides, a transformer circuit can convert an AC waveform on one side into an AC waveform on the other side for output. Transformer circuits can be used to achieve voltage transformation, current transformation, impedance transformation, isolation, and voltage regulation. Transformer circuits can employ magnetic integration technology, using leakage inductance as an energy storage inductor. Using magnetic integration technology, leakage inductance is formed by opening an air gap in the transformer core, serving as the magnetizing inductor to transfer energy. The magnetizing inductor of the transformer circuit is used to achieve zero-voltage switching (ZVS) operation.

[0039] Figure 2 This is a schematic diagram of an AC / DC power converter topology according to an embodiment of this application.

[0040] Please also refer to Figure 1 and Figure 2For example, the AC / DC power converter topology can achieve bidirectional operation, and it can be assumed that forward operation is inversion and reverse operation is rectification.

[0041] For example, during forward operation, the phase shift relationship between the AC and DC sides of the AC-DC power converter can be changed to make the DC-side bridge arm voltage lead the AC-side bridge arm. Similarly, during reverse operation, the phase shift relationship between the AC and DC sides can be changed to make the AC-side bridge arm voltage lead the DC-side bridge arm. This application uses the forward operation process, i.e., inversion, as an example for explanation. The control degrees of freedom of this topology can be defined as the switching frequency, the inward phase shift angle of the primary side, and the outward phase shift angle between the primary and secondary sides.

[0042] The voltage across the inductor varies depending on the operating phase. Based on the voltage applied to the inductor and its duration at each phase, the expression for the output current versus the phase shift angle can be calculated.

[0043] In one embodiment, by fixing the outer phase shift angle and controlling the output current with the switching frequency and the inner phase shift angle as control variables, the function between the output current and the control variables is highly linearized.

[0044] In this embodiment, a frequency conversion control algorithm is used to linearize the nonlinear function of the phase shift angle, so that sinusoidal trajectory tracking can be achieved with simple closed-loop control, thus achieving high-efficiency operation.

[0045] Optionally, the process of obtaining the required output current and input voltage, and calculating the inner phase shift angle of the DC-side bridge arm or AC-side bridge arm based on the transformer circuit, includes: Obtain the number of turns in the transformer circuit to determine the leakage inductance and maximum switching frequency of the power converter; Based on the leakage inductance and maximum switching frequency, the required output current and input voltage are combined to calculate the inner phase shift angle.

[0046] For example, using the transformer turns ratio as the conversion benchmark and leakage inductance and maximum switching frequency as physical constraints, analytical expressions for the required output current, input voltage, and inner phase shift angle are established through inductor volt-second balance and average current matching. Finally, the inner phase shift angle that satisfies the control objective is obtained by solving this equation. The advantage of this calculation process is that all parameters are measurable or designable physical quantities, the analytical equations are simple to solve and easy to implement in engineering, and it lays the foundation for subsequent frequency conversion control and linearization processing.

[0047] Optionally, the difference between the inner phase shift angle of the DC-side bridge arm and the inner phase shift angle of the AC-side bridge arm is taken as the outer phase shift angle; the process of calculating the inner phase shift angle based on the leakage inductance and the maximum switching frequency, and by integrating the required output current and input voltage, includes: Based on the inner phase shift angle, the input voltage, and the outer phase shift angle between the DC side bridge arm and the AC measuring bridge arm, the nodes of the secondary bridge arm are selected as ports for output current analysis to obtain multiple current change points during the operation of the secondary bridge arm. The multiple current change points are connected sequentially by straight line segments in chronological order to determine the linear equations of the multiple line segments respectively. Based on multiple linear equations and the leakage inductance and maximum switching frequency, the average current expression of the secondary bridge arm output is obtained. Obtain the phase shift ratio of the outer phase shift angle to the inner phase shift angle, and calculate the inner phase shift angle based on the average current expression and the required output current.

[0048] For example, the core logic of the entire process is linearization modeling, parameter constraints, and target matching. This process revolves around the calculation of the inner phase shift angle. First, combining the inner phase shift angle, input voltage, and outer phase shift angle, and using the secondary bridge arm node as the analysis port, multiple points of change in the output current during operation are captured. Then, these points of change are connected by straight line segments in chronological order, and the equations of each line segment are determined. The average current expression of the secondary bridge arm output is derived by combining leakage inductance and the maximum switching frequency. Finally, by obtaining the phase shift angle ratio between the outer and inner phase shift angles, this ratio, the average current expression, and the required output current are combined to complete the calculation of the inner phase shift angle. The entire process takes into account both the current variation law and key parameter constraints, ensuring the accuracy and applicability of the calculation results.

[0049] By capturing current change points to achieve piecewise linearization, the complex current dynamics are transformed into a calculable linear equation. An average current model is derived by combining hardware parameters such as leakage inductance and switching frequency. The model is then simplified through phase shift angle proportional constraints, and finally, the inner phase shift angle is solved based on the required output current. This process closely aligns with the actual operating characteristics of the circuit, ensuring model accuracy, simple analytical solution, clear parameter constraints, and engineering feasibility. It lays a crucial foundation for subsequent frequency conversion control and linearization adjustment.

[0050] Optionally, the switching device in the DC-side bridge arm and / or the AC-side bridge arm is a MOSFET, and the process of obtaining the phase shift angle ratio of the outer phase shift angle to the inner phase shift angle includes: Based on the current analysis of the multiple current change points, a first constraint condition is established for the phase shift angle ratio, so that when the current of each switch in the AC / DC power converter maintains its original direction (body diode is conducting), the corresponding switch is turned on, thereby determining the first value range of the phase shift angle ratio. Based on the reactive power analysis during the operation of the AC / DC power converter, a second constraint condition is established for the phase shift angle ratio to minimize the total energy of the reverse return flow in each oscillation cycle of the AC / DC power converter, thereby determining the second value range of the phase shift angle ratio. The phase shift angle ratio is determined based on the first value range and the second value range.

[0051] For example, in the control scheme of AC / DC power converters, the reasonable determination of the phase shift ratio (the ratio of the outer phase shift angle to the inner phase shift angle) is a key link to achieve efficient and stable operation. Its core logic is to establish dual constraints through current characteristic analysis and reactive power optimization, and finally lock in the effective range of the phase shift ratio.

[0052] The switching devices (MOSFETs) in AC / DC power converters contain a body diode structure. The conduction characteristics of the body diode directly affect the operational safety and losses of the switching devices. When the current direction of the switching device is consistent with the conduction direction of the body diode, the body diode can conduct naturally. Controlling the conduction of the switching device at this time can avoid problems such as a surge in switching losses and excessive device stress caused by reverse current (e.g., reverse recovery losses, voltage spikes). The core objective of the first constraint is to ensure that, by limiting the phase shift angle ratio, the current direction of all switching devices is always consistent with the conduction direction of the body diode at the moment of conduction, that is, the current "maintains its original direction," avoiding faults caused by reverse current passing through the switching device or reverse conduction of the body diode.

[0053] Analysis of the output current at the secondary arm nodes reveals "multiple current change points." These change points are essentially critical moments within the switching cycle when the current direction and amplitude undergo abrupt changes (such as the moment of arm commutation or phase shift switching). Considering the power converter topology—a DC-side dual-arm + transformer + AC-side directional switching unit—the generation of current change points is directly related to the relative relationship between the inner and outer phase shift angles: the inner phase shift angle determines the conduction sequence of the internal switching components within the arm, while the outer phase shift angle determines the voltage phase difference between the primary and secondary arms. The proportional relationship between these two factors alters the current flow path and direction within the switching cycle.

[0054] For example, a mathematical relationship between the current direction of each switching device and the phase shift angle ratio can be established by traversing the intervals corresponding to all current change points.

[0055] Specifically, for each switching device, the critical value of the phase shift angle ratio that ensures the current maintains its original direction is derived. For example, when the phase shift angle ratio is less than a certain threshold, the current direction of a certain switching device on the DC side is consistent with that of the body diode; when the phase shift angle ratio is greater than a certain threshold, the current direction of a certain switching device on the AC side meets the requirements.

[0056] Summarize the critical value constraints of all switching devices, take the intersection of all constraints, that is, the phase shift angle ratio must simultaneously meet the current direction requirements of all switching devices, and finally obtain the first value range.

[0057] In typical engineering scenarios, this range needs to avoid bridge arm current overlap caused by an excessively small phase shift angle ratio, and reverse current in the directional switching unit caused by an excessively large phase shift angle ratio. Usually, the first value range will limit the phase shift angle ratio to a certain value. The specific value can be adjusted in combination with hardware parameters such as transformer turns ratio and leakage inductance. The document emphasizes that it is "based on measurable or designable physical quantities", so this range is a parameter-dependent interval.

[0058] For example, in phase-shift control mode, the voltage phase difference between the primary and secondary arms of an AC / DC power converter (determined by the external phase shift angle) leads to "reverse backflow energy," meaning energy flows back from the secondary side to the primary side during the switching cycle, or forms a reactive power cycle within the arm. The essence of this reverse backflow energy is the reverse release of inductor-stored energy caused by voltage mismatch between the primary and secondary sides. This reverse backflow energy is the main source of reactive power, increasing device current stress, power loss, and reducing conversion efficiency. The core objective of the second constraint is to minimize the total reverse backflow energy within each oscillation cycle (switching cycle) by optimizing the phase shift angle ratio, thereby minimizing reactive power.

[0059] For example, the first value range focuses on "safe conduction of switching components" to achieve zero-voltage conduction, which is the bottom-line constraint to ensure reliable and efficient operation of the circuit hardware; the second value range focuses on "minimizing reactive power," which is the performance optimization constraint to achieve efficient operation. The phase shift angle ratio must simultaneously meet the two major goals of "safety" and "efficiency," so the final value range is the intersection of the first and second value ranges.

[0060] Optionally, determining the operating frequency of the transformer circuit based on the inner phase shift angle, so as to linearize the output current as a function of the phase shift angle variable, includes: Based on the phase shift angle ratio and the inner phase shift angle, a switching frequency function is constructed; The operating frequency of the transformer circuit is calculated based on the switching frequency function, so as to linearize the relationship between the output current and the phase shift angle variable using frequency conversion control.

[0061] For example, in the control scheme of AC / DC power converters, constructing a switching frequency function and implementing frequency conversion control is the core step in linearizing the relationship between output current and phase shift angle. Essentially, it utilizes frequency adjustment to compensate for the inherent nonlinearity of phase shift control, enabling a stable linear mapping between the control variable (phase shift angle) and the output quantity (output current), thus providing a foundation for subsequent simple closed-loop control to achieve sinusoidal trajectory tracking.

[0062] In phase-shift control mode, the relationship between output current and phase angle is nonlinear, influenced by factors such as circuit topology, leakage inductance, and switching frequency (e.g., current initially rises rapidly with increasing phase angle and then levels off). The core objective of constructing the switching frequency function is to establish a quantitative relationship between the switching frequency and the ratio of phase angle to the inner phase angle. By dynamically adjusting the switching frequency, the influence of nonlinear factors is offset, ultimately ensuring that the output current and phase angle satisfy a linear equation. The nonlinearity of the output current and phase angle stems from the energy storage effect of the leakage inductance. During the switching cycle, the integral of the voltage across the leakage inductor (volt-second value) determines the change in current, while the phase relationship between voltage and phase angle, as well as the switching frequency, jointly influence the distribution of the volt-second value. To achieve linearization, the change in output current corresponding to a unit change in phase angle can be kept constant through switching frequency adjustment.

[0063] The linearization effect of frequency converter control is mainly reflected in the following aspects: improved linearity reduces the nonlinear error of output current and phase shift angle, ensuring the accuracy of sinusoidal trajectory tracking; dynamic adjustment of switching frequency avoids the surge in switching losses caused by fixed high frequency, and combined with reactive power optimization of phase shift angle ratio, significantly reduces overall power loss. The function model is built based on measurable hardware parameters, making it more adaptable to disturbances such as input voltage fluctuations and leakage inductance tolerance, ensuring stable linearization performance under different operating conditions.

[0064] The core value of constructing the switching frequency function and frequency conversion control lies in offsetting nonlinearity through frequency adjustment. Based on the determined phase shift ratio and analytical relationship of the inner phase shift angle, a targeted frequency function is constructed in conjunction with the circuit hardware parameters. By dynamically adjusting the transformer operating frequency, a stable linear mapping is formed between the output current and the phase shift angle variable. This process not only conforms to the circuit topology characteristics of AC / DC power converters (leakage inductance energy storage, phase shift control mechanism) but also takes into account the simplicity of engineering implementation (analytical solution, measurable parameters), ultimately providing key technical support for simple closed-loop control, high-efficiency operation, and sinusoidal trajectory tracking.

[0065] Figure 3 This is a schematic diagram of an AC / DC power converter circuit according to an embodiment of this application.

[0066] like Figure 3 As shown, optionally, the AC / DC power converter includes a DC-side bridge arm, a transformer circuit N1, and an AC-side bridge arm connected in sequence, wherein: The DC side bridge arm includes a first bridge arm B1 and a second bridge arm B2, and the AC side bridge arm includes a first directional switch unit K1, a second directional switch unit K2, a first capacitor C1 and a second capacitor C2. The first end of the first bridge arm B1 and the first end of the second bridge arm B2 are connected to the positive terminal of the DC bus, the second end of the first bridge arm B1 and the second end of the second bridge arm B2 are connected to the negative terminal of the DC bus, the switch selection terminal of the first bridge arm B1 is connected to the first terminal of the DC side of the transformer circuit N1, and the switch selection terminal of the second bridge arm B2 is connected to the second terminal of the DC side of the transformer circuit N1.

[0067] The first end of the first directional switch unit K1 is connected to the live wire end of the AC bus, the second end of the first directional switch unit K1 is connected to the second end of the second directional switch unit K2 and the first end of the AC side of the transformer circuit N1, and the first end of the second directional switch unit K2 is connected to the neutral wire end of the AC bus.

[0068] The first end of the first capacitor C1 is connected to the first end of the first directional switch unit K1, the second end of the first capacitor C1 is connected to the second end of the second capacitor C2, the first end of the second capacitor C2 is connected to the first end of the second directional switch unit K2, and the second end of the AC side of the transformer circuit N1 is connected to the common terminal of the first capacitor C1 and the second capacitor C2.

[0069] For example, the AC / DC power converter topology adopts a core architecture in which the DC-side bridge arm, transformer circuit N1, and AC-side bridge arm are connected in sequence. The DC side is connected to the positive and negative terminals of the DC bus through the first bridge arm B1 and the second bridge arm B2, and achieves a precise connection with the DC side of the transformer circuit N1, providing stable DC-side support for power conversion. The AC side innovatively integrates the first directional switch unit K1, the second directional switch unit K2, and two capacitors. The directional switch units are respectively connected to the live wire and neutral wire of the AC bus, and the capacitors are connected to the AC side of the transformer circuit N1 through a common terminal. This not only ensures the directional flow and phase matching of the AC side current, but also optimizes the voltage distribution and filtering performance of the circuit through capacitor configuration. The overall topology design takes into account the needs of bidirectional power conversion.

[0070] For example, a MOSFET switch, also known as a MOS transistor, has three pins, typically a gate, a source, and a drain. The conduction and cutoff of the drain and source can be changed by applying a control signal between the gate and source. Optionally, the switch in the bridge arm can be an N-type MOS transistor. A MOS transistor has a body diode.

[0071] For example, the first directional switching unit K1 can be switched on towards the AC grid during the positive half-cycle of the AC bus and towards the transformer during the negative half-cycle. The second directional switching unit K2 can be switched on towards the AC source during the negative half-cycle of the AC bus and towards the transformer during the positive half-cycle. This allows the circuit control to flexibly control the direction of the current under different conditions. For example, the first capacitor C1 and the second capacitor C2 can store or release electrical charge during different oscillation cycles, thereby forming electromagnetic oscillations with the inductive component in the circuit. For example, the transformer circuit N1 using magnetic integration technology has leakage inductance due to its magnetic flux characteristics, which can act as an energy storage inductor. By directionally controlling the first directional switching unit K1 and the second directional switching unit K2 under different half-cycle currents, a suitable AC waveform can be provided to the transformer circuit N1 during AC-to-DC conversion, or a suitable AC waveform can be output during DC-to-AC conversion.

[0072] Optionally, the first directional switch unit K1 includes a fifth switch element S5, a sixth switch element S6, a first diode D1, and a second diode D2; The first end of the fifth switching element S5 is connected to the first end of the first directional switching unit K1, the second end of the fifth switching element S5 is connected to the anode of the first diode D1, and the cathode of the first diode D1 is connected to the second end of the first directional switching unit K1. The first end of the sixth switch S6 is connected to the second end of the first directional switch unit K1, the second end of the sixth switch S6 is connected to the anode of the second diode D2, and the cathode of the second diode D2 is connected to the first end of the first directional switch unit K1.

[0073] For example, a diode is an electronic device made of semiconductor materials (silicon, selenium, germanium, etc.). A diode has two electrodes: a positive electrode, also called the anode, and a negative electrode, also called the cathode. When a forward voltage is applied between the two electrodes, the diode conducts; when a reverse voltage is applied, the diode is cut off. A diode has unidirectional conductivity; when conducting, the current flows from the anode through the diode to the cathode. The conduction and cutoff of a diode are equivalent to the switching on and off of a switch.

[0074] For example, by using a diode and a switching element in series, it is possible to ensure that the current can flow unidirectionally in a predetermined branch. The series connection of the fifth switching element S5 with the first diode D1 can limit the current in this branch to flow from the AC bus toward the transformer. The series connection of the sixth switching element S6 with the second diode D2 can limit the current in this branch to flow from the transformer toward the AC bus.

[0075] Optionally, the second directional switch unit K2 includes a seventh switch element S7 and an eighth switch element S8. The first end of the seventh switch element S7 is connected to the first end of the second directional switch unit K2, the second end of the seventh switch element S7 is connected to the first end of the eighth switch element S8, and the second end of the eighth switch element S8 is connected to the second end of the second directional switch unit K2.

[0076] For example, the first directional switch unit K1 and the second directional switch unit K2 are connected in reverse through two switches, enabling one switch to be controlled to be normally open for a period of time via a control terminal. When the other switch is controlled to be in a cyclic switching state, the direction selection and limitation of the circuit can be achieved.

[0077] Optionally, the first bridge arm B1 includes a first switch S1 and a second switch S2, and the second bridge arm B2 includes a third switch S3 and a fourth switch S4. The first end of the first switch S1 is connected to the positive terminal of the DC bus, the first end of the second switch S2 is connected to the second end of the first switch S1, and the second end of the second switch S2 is connected to the negative terminal of the DC bus; the first end of the third switch S3 is connected to the positive terminal of the DC bus, the first end of the fourth switch S4 is connected to the second end of the third switch S3, and the second end of the fourth switch S4 is connected to the negative terminal of the DC bus. The first end of the DC side of the transformer circuit N1 is connected to the common terminal of the first switch S1 and the second switch S2, and the second end of the DC side of the transformer circuit N1 is connected to the common terminal of the third switch S3 and the fourth switch S4.

[0078] For example, the DC-side dual bridge arms (first and second bridge arms B2) adopt a classic and reliable half-bridge topology. The first bridge arm B1 consists of the first and second switches S2 connected in series, and the second bridge arm B2 consists of the third and fourth switches S4 connected in series. Both bridge arms are connected in parallel between the positive and negative poles of the DC bus, forming a symmetrical layout. The two ends of the DC side of the transformer circuit N1 are respectively connected to the common terminals of the upper and lower switches in the two bridge arms. This connection method can flexibly adjust the voltage amplitude and phase output to the DC side of the transformer by controlling the turn-on and turn-off sequence of the four switches, providing a hardware basis for the realization of the inner phase shift angle. At the same time, the half-bridge topology combined with the symmetrical connection design not only ensures the stable transmission of DC-side energy, but also reduces current stress through the complementary operation of the switches, which meets the bidirectional operation requirements of the AC-DC power converter and supports subsequent phase shift control and frequency conversion control.

[0079] Optionally, the AC / DC power converter operates during the DC-to-AC conversion process, and the process of generating control logic for the switching elements in the DC-side bridge arm or AC-side bridge arm based on the inner phase shift angle and the operating frequency includes: During the positive half-cycle of the AC bus, the sixth switch S6 and the eighth switch S8 are controlled to be normally on, and the fifth switch S5 and the seventh switch S7 are controlled to operate in a high-frequency complementary switching state.

[0080] For example, in the DC-to-AC conversion process of the AC power converter, the control logic design of its switching components is specifically targeted and coordinated for the positive half-cycle of the AC bus. By controlling the sixth switch S6 of the first directional switching unit K1 and the eighth switch S8 of the second directional switching unit K2 on the AC side to remain constantly open, a stable basic path for the current flow on the AC side is provided. At the same time, the fifth switch S5 of the first directional switching unit K1 and the seventh switch S7 of the second directional switching unit K2 are controlled to operate in a high-frequency complementary switching state. Combined with the calculated internal phase shift angle and the transformer operating frequency, precise current regulation and efficient energy transmission are achieved. This control logic not only matches the current phase characteristics of the positive half-cycle of AC, but also meets the requirements of phase shift control and frequency conversion control, ensuring the linearization of the output current and the sinusoidal trajectory tracking effect, while minimizing switching losses and reactive power.

[0081] Figure 4 This is a timing diagram of the operation of an AC / DC power converter according to an embodiment of this application.

[0082] like Figure 4 As shown, optionally, the process of controlling the sixth switch S6 and the eighth switch S8 to be normally on, and controlling the fifth switch S5 and the seventh switch S7 to operate in a high-frequency complementary switching state, further includes: From the first moment to the second moment, control the first switch S1 and the fourth switch S4 to be turned on, control the second switch S2 and the third switch S3 to be turned off, control the seventh switch S7 to be turned on, and control the fifth switch S5 to be turned off; From the second time point to the third time point, the first switch S1 and the fourth switch S4 are turned on, the second switch S2 and the third switch S3 are turned off, the fifth switch S5 is turned on, and the seventh switch S7 is turned off. From the third moment to the fourth moment, control the second switch S2 and the fourth switch S4 to be turned on, control the first switch S1 and the third switch S3 to be turned off, control the fifth switch S5 to be turned on, and control the seventh switch S7 to be turned off. From the fourth moment to the fifth moment, the first switch S1 and the fourth switch S4 are turned on, the second switch S2 and the third switch S3 are turned off, the fifth switch S5 is turned on, and the seventh switch S7 is turned off. From the fifth moment to the sixth moment, control the second switch S2 and the third switch S3 to be turned on, control the first switch S1 and the fourth switch S4 to be turned off, control the seventh switch S7 to be turned on, and control the fifth switch S5 to be turned off. From the sixth to the seventh moment, the second switch S2 and the fourth switch S4 are turned on, the first switch S1 and the third switch S3 are turned off, the seventh switch S7 is turned on, and the fifth switch S5 is turned off.

[0083] Under the positive half-cycle operation of the AC bus in the DC-to-AC conversion of the AC-DC power converter, while maintaining the sixth switch (S6) and eighth switch (S8) as normally closed and the fifth switch (S5) and seventh switch (S7) as high-frequency complementary switches, this control logic further refines the switching sequence of the switches from the first to the seventh time interval. It precisely controls the conduction combination of the first to fourth switches on the DC side in time-segmented manner, such as conducting the first and fourth switches from the first to the second time interval, and conducting the second and fourth switches from the third to the fourth time interval. This is synchronized with the alternating conduction and disconnection of the fifth and seventh switches, ensuring that the switch control meets the requirements of the internal phase shift angle and the transformer's operating frequency. Furthermore, the timing subdivision achieves smooth current transition and precise regulation, effectively reducing switching losses and reactive power, and ensuring linearization of the output current and sinusoidal trajectory tracking.

[0084] Second Embodiment Building upon the first embodiment, this application also provides a bidirectional AC / DC power converter using a high-efficiency single-stage dual active bridge (DAB) microinverter. It employs a novel modulation strategy to minimize the reactive power of the dual active bridge converter. Through this modulation strategy, the dual active bridge microinverter achieves good controllability and high efficiency. It aims to achieve the following three objectives: First, the frequency conversion control algorithm linearizes the nonlinear function of the phase shift angle, thus enabling sinusoidal trajectory tracking to be achieved with simple closed-loop control.

[0085] Second, the modulation strategy minimizes reactive power during the switching cycle while ensuring all switches achieve zero-voltage turn-on (ZVS). Due to the minimization of reactive power, current stress and power loss are significantly reduced, thus enabling this dual active bridge microinverter to achieve maximum efficiency.

[0086] Third, the proposed phase shift angle and switching frequency are obtained in analytical form, so the calculation is simple and easy to implement.

[0087] The working principle of the modulation strategy is theoretically analyzed and verified below. Experiments are conducted through simulation to evaluate the performance of the proposed inverter and verify the correctness of the theoretical analysis.

[0088] Please continue to refer to this. Figure 3 This AC / DC power converter circuit topology can operate in both directions: forward rotation for inversion and reverse rotation for rectification. Please refer to [reference needed]. Figure 4 The time series diagram shows that time periods 1–3 and 4–6 are symmetrical.

[0089] The entire switching cycle can be subdivided into six different operating modes: three modes on the positive AC half-axis and three modes on the negative AC half-axis, with the two sides being symmetrical to each other.

[0090] The AC / DC power converter system uses a dual active bridge architecture. A bidirectional switch on the high-voltage side works in conjunction with the power grid to achieve commutation. The first and second capacitors are used to form the other half-bridge, and only one high-voltage bridge arm is used to save costs. Therefore, the control degrees of freedom of this topology are: switching frequency f, primary side inward phase shift angle φ (i.e., the DC side bridge arm inward phase shift angle), and primary-secondary side outward phase shift angle φ (i.e., the difference between the DC side bridge arm inward phase shift angle and the AC side bridge arm inward phase shift angle). Calculations show that the AC side switching device withstands a voltage of 0.5Vg, where Vg is the AC side bus voltage. Therefore, when the AC side MOSFET is connected to the power grid on the AC side, it does not need a high withstand voltage of 230V; a withstand voltage of 115V or higher is sufficient, effectively reducing device costs.

[0091] Please also refer to Figure 3 and Figure 4 The AC / DC power converter can be set to operate for time t and have a cycle of TS. During operation, time intervals are defined as follows: t0-t1 (time interval 1), t1-t2 (time interval 2), t2-t3 (time interval 3), and t3-t4 (time interval 4). The operating voltages of the first switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, sixth switch S6, and eighth switch S8 are Vs1, Vs2, Vs3, Vs4, Vs6, Vs7, and Vs8, respectively. Ppv represents the DC bus input power, and is represents the transformer secondary output current.

[0092] Figure 5 This is a schematic diagram of the control logic of an embodiment of this application.

[0093] Please refer to Figure 5As shown, Io* is the reference current, io is the required output current; vg is the AC bus voltage, i.e., the required output voltage; Vpv is the DC bus voltage. Fs is the operating frequency, fs,max is the maximum operating frequency, k is the phase shift ratio, and D is the duty cycle. The combination of phase shift modulation and frequency conversion modulation in the dual active bridge topology enables soft switching of all switching transistors across the entire AC voltage range.

[0094] The control logic for the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 is as follows: On the DC side, the first switch S1 and the fourth switch S4 are simultaneously turned on, as are the second switch S2 and the third switch S3. The first switch S1 and the second switch S2 provide complementary outputs; these two switches are called the leading arms. The third switch S3 and the fourth switch S4 provide complementary outputs; these two switches are called the lagging arms.

[0095] In this logic, the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 are complementary, and the diagonal switches open together.

[0096] We can define the first switch S1 and the second switch S2 as leading the third switch S3 and the fourth switch S4 by an inward phase shift φ on the primary side. There is a phase shift angle between the AC and DC sides called the outward phase shift φ. The relationship between the two can be established as follows: φ= kφ For example, in the control logic of the fifth switch S5, the sixth switch S6, the seventh switch S7, and the eighth switch S8, Table 1 is the truth table of the control logic during the positive and negative half-axis of the AC circuit.

[0097] When the AC side voltage is operating in the positive half-cycle, the sixth switch S6 and the eighth switch S8 are normally on, and the fifth switch S5 and the seventh switch S7 are operating in the high-frequency switching state. During the negative half-cycle, the fifth switch S5 and the seventh switch S7 are normally on, while the sixth switch S6 and the eighth switch S8 operate in a high-frequency switching state.

[0098] Table 1. Truth Table of Control Logic During AC Positive Half-Shaft Load Half-Shaft Period

[0099] Define the phase shift duty cycle as D = φ1 / π, where φ1 is the phase shift angle inside the AC side bridge arm.

[0100] The voltages across the inductor at different stages are n*Vpv+0.5*vg, n*Vpv-0.5*vg, and 0.5*vg, respectively (Vpv is the DC bus voltage, and vg is the AC bus voltage). Based on the voltages applied to the inductor and their durations at different stages, the formulas for the output current and phase shift angle can be calculated, as can the formulas for the negative half-axis. These are also the voltages corresponding to the six modes mentioned earlier. Due to the symmetrical structure, we will discuss the half-case scenario below.

[0101] Zero-voltage switching (ZVS) is achieved through freewheeling in the body diode. If freewheeling occurs in the body diode of a switching device at a certain moment, the device can send a turn-on signal, thus achieving zero-voltage switching control. The conditions for freewheeling are constrained by relevant formulas. For example, because these are synchronous MOSFETs, each MOSFET has an independent power supply. When freewheeling occurs, the MOSFET is energized and can be controlled. During the freewheeling period, when the voltage is clamped by the body diode, turning on the MOSFET results in a very low voltage, thus achieving zero-voltage switching control.

[0102] Figure 6 This is a schematic diagram of the operating timing of an AC / DC power converter according to an embodiment of this application.

[0103] like Figure 6 As shown, in one embodiment, the current at each time node is analyzed based on the circuit topology principle. The nodes of the secondary bridge are selected as ports for analysis; based on the known point coordinates and time nodes t1, t2, and t3, the equations of lines AB, BC, and CD in the timing diagram are determined respectively. At least the peak currents at the three nodes in the diagram can be determined as follows: I1 =(T*(vg - 4*Vpv*φ*n + 8*k*Vpv*φ*n)) / (8*L) I2 =(T*( vg - 4* vg *φ+ 4*k* vg *φ + 4*Vpv*φ*n)) / (8*L) I3 =(T*(4*k* vg *φ- vg + 4*Vpv*φ*n)) / (8*L) Where I1 is the peak current at time t1, I2 is the peak current at time t2, I3 is the peak current at time t3, n is the number of transformer turns, and L is the magnetizing inductance. Therefore, in this circuit topology, the average current is a linear function of two variables with respect to the direction shift angle.

[0104] Furthermore, in the control algorithm proposed in this embodiment, the expression for the switching frequency function fs(φ) is: fs(φ)=(1-mφ)fs,max m=2*(2k)2 -2k+1) Where fs,max is the maximum switching frequency.

[0105] For example, in order to determine the relationship between the external phase shift of the control variable and the output current, the internal phase shift angle φ of the primary side can be calculated according to the following expression:

[0106] Figure 7 This is a schematic diagram illustrating the linearization of the output current and control variables according to an embodiment of this application.

[0107] like Figure 7 As shown, to achieve a high degree of linearity between the output current and the control variable, the outer phase shift angle can be fixed, and control can be achieved through the switching frequency and the inner phase shift angle. This facilitates determining the primary side inner phase shift angle based on the required output current.

[0108] Where io is the required output current.

[0109] For example, before the switching transistor is turned on, the current maintains its original direction, that is, the body diode remains on, which can achieve zero-voltage conduction. This requires that the peak currents I1, I2, and I3 at the three moments be greater than 0. At this time, the value of k reasonably exists within the first range, ensuring that when the current is greater than 0, freewheeling can be achieved, thus realizing zero-voltage conduction.

[0110] On the other hand, at a given grid voltage, increasing the phase shift index k will increase reactive power Qre. Therefore, the phase shift index k should be adjusted to a small value to minimize reactive power Qre.

[0111] For example, reactive power Qre can be calculated according to the following expression: Qre=n*Vpv((n*Vpv+k*vg)*φ-0.25*vg) 2 / 4*L*fs(4*L*fs(φ)+0.5*vg) Reducing the value of k limits the zero-voltage turn-on range of the switches. Zero-voltage turn-on is crucial for improving power conversion efficiency. Therefore, the zero-voltage turn-on condition should be considered when adjusting the phase shift index k. From the polarity of the leakage current, the zero-voltage turn-on condition for the dual active bridge (DAB) microinverter can be calculated as follows: when the current I1 > 0 at time t1, ZVS turn-on of switches S5-S8 is possible. At this point, a smaller second value range can be found within the first value range.

[0112] In other words, the proposed control method requires a trade-off between zero-voltage conduction and unwanted power, ensuring that zero-voltage conduction can be achieved while minimizing unwanted power.

[0113] Figure 8 This is a schematic diagram of the waveform generated during simulation verification of an embodiment of this application.

[0114] like Figure 8 As shown, the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 continuously emit high-frequency waves, while the fifth switch S5 and the seventh switch S7 on the positive half-axis of AC perform high-frequency chopping. By adjusting k according to the input voltage, the proposed modulation scheme can minimize reactive power and improve power conversion efficiency.

[0115] Figure 9 This is a schematic diagram showing the timing details of a bridge arm switch according to an embodiment of this application.

[0116] like Figure 9 As shown, there is an internal phase shift of φ between the first switch S1 and the fourth switch S4, and an external phase shift of φ between the fourth switch S4 and the fifth switch S5. The relationship between the two is: φ = kφ.

[0117] Figure 10 This is a schematic diagram of the voltage and current across a transformer according to an embodiment of this application. Figure 11 This is a schematic diagram of the voltage across an inductor according to an embodiment of this application.

[0118] like Figure 10 As shown, the top is the current waveform, and the bottom is the voltage waveform. Figure 11 As shown, the voltage across the inductor is different at different stages, and can be calculated separately.

[0119] Third Embodiment This application also provides a storage medium storing a computer program, which, when executed by a processor, implements the steps of the AC / DC power converter control method described above.

[0120] The AC / DC power converter control method and storage medium provided in this application obtain the required output current and input voltage, and calculate the inner phase shift angle of the DC-side bridge arm or AC-side test bridge arm according to the transformer circuit. The inner phase shift angle includes the inner phase shift angle of the DC-side bridge arm or the inner phase shift angle of the AC-side test bridge arm. Based on the inner phase shift angle, the operating frequency of the transformer circuit is determined to linearize the function of the output current and the phase shift angle variable. Based on the inner phase shift angle and the operating frequency, the control logic of the switching devices in the DC-side bridge arm or AC-side test bridge arm is generated. The nonlinear function of the phase shift angle can be linearized using a frequency conversion control algorithm, so that sinusoidal trajectory tracking can be achieved with simple closed-loop control. The proposed modulation strategy minimizes reactive power during the switching cycle while ensuring that all switches achieve zero-voltage turn-on (ZVS). Due to the minimization of reactive power, current stress and power loss are significantly reduced, thus achieving high-efficiency operation of the dual active bridge (DAB) micro-inverter. The proposed phase shift angle and switching frequency can be obtained in analytical form, which is simple to calculate and easy to implement, thereby improving the user experience.

[0121] In the embodiments of the smart terminal and storage medium provided in this application, all the technical features of any of the above-described method embodiments may be included. The extended and explanatory content of the specification is basically the same as that of the embodiments of the above methods, and will not be repeated here.

[0122] This application also provides a computer program product, which includes computer program code. When the computer program code is run on a computer, it causes the computer to perform the methods described in the various possible implementations above.

[0123] This application also provides a chip, including a memory and a processor. The memory is used to store a computer program, and the processor is used to call and run the computer program from the memory, so that a device with the chip installed performs the methods described in the various possible implementations above.

[0124] It is understood that the above scenarios are merely examples and do not constitute a limitation on the application scenarios of the technical solutions provided in the embodiments of this application. The technical solutions of this application can also be applied to other scenarios. For example, as those skilled in the art will know, with the evolution of system architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0125] 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.

[0126] The steps in the method of this application embodiment can be adjusted, combined, or deleted according to actual needs.

[0127] The units in the device of this application embodiment can be merged, divided, and deleted according to actual needs.

[0128] In this application, the same or similar terms, concepts, technical solutions and / or application scenario descriptions are generally described in detail only when they appear for the first time. When they appear again, they are generally not repeated for the sake of brevity. When understanding the technical solutions and other contents of this application, the same or similar terms, concepts, technical solutions and / or application scenario descriptions that are not described in detail later can be referred to their previous relevant detailed descriptions.

[0129] In this application, the descriptions of the various embodiments have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0130] The technical features of the present application can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the present application.

[0131] 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, controlled terminal, or network device, etc.) to execute the methods of each embodiment of this application.

[0132] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a storage medium or transmitted from one storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line) or wireless (e.g., infrared, wireless, microwave, etc.) means. The storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, storage disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid state disk (SSD)).

[0133] The above are merely preferred 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 control method for an AC / DC power converter, characterized in that, The AC / DC power converter includes a DC-side bridge arm, a transformer circuit, and an AC-side bridge arm connected in sequence. The control method for the AC / DC power converter includes: Obtain the required output current and input voltage, and calculate the inner phase shift angle of the DC side bridge arm or the AC measuring bridge arm according to the transformer circuit; the inner phase shift angle includes the inner phase shift angle of the DC side bridge arm or the inner phase shift angle of the AC measuring bridge arm; Based on the inner phase shift angle, the operating frequency of the transformer circuit is determined so that the output current is linearized as a function of the phase shift angle variable; Based on the internal phase shift angle and the operating frequency, control logic for the switching components in the DC-side bridge arm or AC-side bridge arm is generated.

2. The AC / DC power converter control method according to claim 1, characterized in that, The process of obtaining the required output current and input voltage, and calculating the inner phase shift angle of the DC side bridge arm or AC side bridge arm based on the transformer circuit, includes: Obtain the number of turns in the transformer circuit to determine the leakage inductance and maximum switching frequency of the power converter; Based on the leakage inductance and maximum switching frequency, the required output current and input voltage are combined to calculate the inner phase shift angle.

3. The AC / DC power converter control method according to claim 2, characterized in that, The difference between the inner phase shift angle of the DC-side bridge arm and the inner phase shift angle of the AC-side bridge arm is taken as the outer phase shift angle; the process of calculating the inner phase shift angle based on the leakage inductance and the maximum switching frequency, and by integrating the required output current and input voltage, includes: Based on the inner phase shift angle, the input voltage, and the outer phase shift angle between the DC side bridge arm and the AC measuring bridge arm, the nodes of the secondary bridge arm are selected as ports for output current analysis to obtain multiple current change points during the operation of the secondary bridge arm. The multiple current change points are connected sequentially by straight line segments in chronological order to determine the linear equations of the multiple line segments respectively. Based on multiple linear equations and the leakage inductance and maximum switching frequency, the average current expression of the secondary bridge arm output is obtained. Obtain the phase shift ratio of the outer phase shift angle to the inner phase shift angle, and calculate the inner phase shift angle based on the average current expression and the required output current.

4. The AC / DC power converter control method according to claim 3, characterized in that, The switching devices in the DC-side bridge arm and / or the AC-side bridge arm are MOSFETs. The process of obtaining the phase shift angle ratio of the outer phase shift angle to the inner phase shift angle includes: Based on the current analysis of the multiple current change points, a first constraint condition is established for the phase shift angle ratio, so that when the current of each switch in the AC / DC power converter maintains its original direction (body diode is conducting), the corresponding switch is turned on, thereby determining the first value range of the phase shift angle ratio. Based on the reactive power analysis during the operation of the AC / DC power converter, a second constraint condition is established for the phase shift angle ratio to minimize the total energy of the reverse return flow in each oscillation cycle of the AC / DC power converter, thereby determining the second value range of the phase shift angle ratio. The phase shift angle ratio is determined based on the first value range and the second value range.

5. The AC / DC power converter control method according to claim 1, characterized in that, The process of determining the operating frequency of the transformer circuit based on the inner phase shift angle, so as to linearize the function of the output current and the phase shift angle variable, includes: Based on the phase shift angle ratio and the inner phase shift angle, a switching frequency function is constructed; The operating frequency of the transformer circuit is calculated based on the switching frequency function, so as to linearize the relationship between the output current and the phase shift angle variable using frequency conversion control.

6. A control method for an AC / DC power converter according to any one of claims 1-5, characterized in that, The AC / DC power converter includes a DC-side bridge arm, a transformer circuit, and an AC measuring bridge arm connected in sequence, wherein: The DC side bridge arm includes a first bridge arm and a second bridge arm, and the AC side bridge arm includes a first directional switch unit, a second directional switch unit, a first capacitor and a second capacitor; The first end of the first bridge arm and the first end of the second bridge arm are connected to the positive terminal of the DC bus, the second end of the first bridge arm and the second end of the second bridge arm are connected to the negative terminal of the DC bus, the switch selection terminal of the first bridge arm is connected to the first terminal of the DC side of the transformer circuit, and the switch selection terminal of the second bridge arm is connected to the second terminal of the DC side of the transformer circuit. The first end of the first directional switch unit is connected to the live wire end of the AC bus, the second end of the first directional switch unit is connected to the second end of the second directional switch unit and the first end of the AC side of the transformer circuit, and the first end of the second directional switch unit is connected to the neutral wire end of the AC bus. The first terminal of the first capacitor is connected to the first terminal of the first directional switch unit, the second terminal of the first capacitor is connected to the second terminal of the second capacitor, the first terminal of the second capacitor is connected to the first terminal of the second directional switch unit, and the second terminal of the AC side of the transformer circuit is connected to the common terminal of the first capacitor and the second capacitor.

7. The AC / DC power converter control method according to claim 6, characterized in that, The first directional switching unit includes a fifth switching element, a sixth switching element, a first diode, and a second diode D2; The first end of the fifth switching element is connected to the first end of the first directional switching unit, the second end of the fifth switching element is connected to the anode of the first diode, and the cathode of the first diode is connected to the second end of the first directional switching unit. The first end of the sixth switching element is connected to the second end of the first directional switching unit, the second end of the sixth switching element is connected to the anode of the second diode D2, and the cathode of the second diode D2 is connected to the first end of the first directional switching unit; And / or, The second directional switch unit includes a seventh switch element and an eighth switch element. The first end of the seventh switch element is connected to the first end of the second directional switch, the second end of the seventh switch element is connected to the first end of the eighth switch element, and the second end of the eighth switch element is connected to the second end of the second directional switch unit. And / or, The first bridge arm includes a first switch and a second switch, and the second bridge arm includes a third switch and a fourth switch; The first end of the first switch is connected to the positive terminal of the DC bus; the first end of the second switch is connected to the second end of the first switch; and the second end of the second switch is connected to the negative terminal of the DC bus. The first end of the third switch is connected to the positive terminal of the DC bus; and the first end of the fourth switch is connected to the second end of the third switch; and the second end of the fourth switch is connected to the negative terminal of the DC bus. The first end of the DC side of the transformer circuit is connected to the common terminal of the first switch and the second switch, and the second end of the DC side of the transformer circuit is connected to the common terminal of the third switch and the fourth switch.

8. The AC / DC power converter control method according to claim 7, characterized in that, The AC / DC power converter operates during the DC-to-AC conversion process. The process of generating control logic for the switching components in the DC-side bridge arm or AC-side bridge arm based on the internal phase shift angle and the operating frequency includes: During the positive half-cycle of the AC bus, the sixth and eighth switches are controlled to be normally on, and the fifth and seventh switches are controlled to operate in a high-frequency complementary switching state.

9. The AC / DC power converter control method according to claim 8, characterized in that, The process of controlling the sixth and eighth switches to be normally on and controlling the fifth and seventh switches to operate in a high-frequency complementary switching state also includes: From the first moment to the second moment, control the first and fourth switches to be turned on, control the second and third switches to be turned off, control the seventh switch to be turned on, and control the fifth switch to be turned off; From the second time point to the third time point, the first and fourth switches are turned on, the second and third switches are turned off, the fifth switch is turned on, and the seventh switch is turned off. From the third to the fourth moment, the second and fourth switches are turned on, the first and third switches are turned off, the fifth switch is turned on, and the seventh switch is turned off. From the fourth moment to the fifth moment, control the first switch and the fourth switch to be turned on, control the second switch and the third switch to be turned off, control the fifth switch to be turned on, and control the seventh switch to be turned off; From the fifth moment to the sixth moment, control the second and third switches to be turned on, control the first and fourth switches to be turned off, control the seventh switch to be turned on, and control the fifth switch to be turned off; From the sixth to the seventh moment, the second and fourth switches are turned on, the first and third switches are turned off, the seventh switch is turned on, and the fifth switch is turned off.

10. A storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, implements the steps of the AC / DC power converter control method as described in any one of claims 1-9.

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