Design Method of Inverter with Separable Phase Output and Its Coupling Inductor

Abstract

An embodiment of the present invention discloses an inverter with separable-phase output and a design method for its coupled inductor. By regarding the sine modulation signal of the inverter topology circuit and the coupling coefficient as variables, a first functional relationship is obtained, and the first functional relationship is analyzed to obtain a second functional relationship between the coupled inductor and the maximum value of the first ripple current and the coupling coefficient under the selected connection mode of the inverter topology circuit. Based on the maximum value of the first ripple current determined by the second functional relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected with a discrete inductor, a target coupling coefficient that satisfies the maximum value of the first ripple current corresponding to each inductor coil being less than the maximum value of the second ripple current is determined, so that the self-inductance of the coupled inductor can be smaller relative to the inverter connected with a discrete inductor by the inverter topology circuit, and further the volume and weight of the coupled inductor can be smaller, which is beneficial to reducing the core loss.

Description

Technical Field

[0001] The present invention relates to the technical field of power conversion, and particularly to an inverter with split-phase output and a design method for its coupled inductor. Background Art

[0002] With the diversification of the requirements of power consumption systems, inverters with split-phase output are increasingly widely used.

[0003] For an inverter with split-phase output, a pair of discrete filter inductors are usually required for output current filtering. The use of discrete filter inductors results in relatively large inductor volume, weight, and core loss.

[0004] Therefore, there is an urgent need to use a coupled inductor for filtering in a split-phase output inverter. Correspondingly, the parameter design of the coupled inductor becomes an urgent problem to be solved. Summary of the Invention

[0005] The present invention provides an inverter with split-phase output and a design method for its coupled inductor, so as to realize the parameter design of the coupled inductor in the inverter with split-phase output, use the coupled inductor for filtering in the inverter, reduce the self-inductance, and reduce the volume, weight, and core loss of the inductor.

[0006] According to one aspect of the present invention, a design method for a coupled inductor in an inverter with split-phase output is provided. The inverter includes an inverter topology circuit and a coupled inductor; the inverter topology circuit includes a topology input end and at least two topology output ends, and the inverter topology circuit is configured to output a split-phase square wave voltage through the topology output ends according to an input signal at the topology input end; the inverter includes at least two split-phase output ends; the coupled inductor includes at least two inductor coils, and the inductor coils are connected between the topology output ends and the split-phase output ends;

[0007] The design method includes:

[0008] According to the connection mode of the selected coupled inductor and the inverter topology circuit, determine the first functional relationship between the ripple current of the inductor coil, the coupling coefficient of the coupled inductor, and the sine modulation signal for pulse width modulation of the inverter topology circuit; the connection mode includes that the like-named ends of each inductor coil are respectively connected to the corresponding topology output end, or respectively connected to the corresponding split-phase output end; or the like-named ends of some inductor coils are connected to the corresponding topology output end, or the like-named ends of some inductor coils are connected to the corresponding split-phase output end;

[0009] Determine the second functional relationship between the maximum value of the first ripple current on the inductor coil and the coupling coefficient of the coupled inductor according to the first functional relationship;

[0010] Determine the target coupling coefficient based on the maximum value of the first ripple current determined according to the second functional relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor; wherein, under the target coupling coefficient, the maximum value of the first ripple current corresponding to each inductor coil is less than the corresponding maximum value of the second ripple current.

[0011] Optionally, according to the connection method of the selected coupled inductor and the inverter topology circuit, determine the first functional relationship between the ripple current of the inductor coil, the coupling coefficient of the coupled inductor, and the sinusoidal modulation signal for pulse width modulation of the inverter topology circuit, including:

[0012] Determine the voltage equation of the coupled inductor according to the selected connection method; the voltage equation of the coupled inductor includes the relationship equation between the inductor voltage on the inductor coil, the current change rate of the inductor coil, the self-inductance value of the inductor coil, and the mutual inductance value.

[0013] According to the voltage equation of the coupled inductor, determine the third functional relationship between the current change rate of the inductor coil and the coupling coefficient.

[0014] According to the third functional relationship and the relationship between the time when the output voltage at the topology output end is not equal to 0 within the power frequency period and the sinusoidal modulation signal, determine the first functional relationship.

[0015] Optionally, according to the voltage equation, determine the third functional relationship between the current change rate of the inductor coil and the coupling coefficient, including:

[0016] Use the difference between the topology output voltage at the topology output end and the split-phase voltage output at the split-phase output end to replace the inductor voltage in the voltage equation to determine the third functional relationship.

[0017] Optionally, according to the first functional relationship, determine the second functional relationship between the maximum value of the first ripple current on the inductor coil and the coupling coefficient of the coupled inductor, including:

[0018] Determine the relationship satisfied between the sinusoidal modulation signal and the coupling coefficient when the ripple current is the largest according to the first functional relationship;

[0019] According to the relationship satisfied between the sinusoidal modulation signal and the coupling coefficient and the first functional relationship, determine the second functional relationship.

[0020] Optionally, according to the second functional relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor, determine the target coupling coefficient, including:

[0021] Determine the target coupling coefficient according to the second function relationship, the maximum value of the second ripple current on the discrete inductor, and the preset conditions under the condition that the inverter topology circuit is connected to the discrete inductor; wherein, the preset conditions include that the ratio of the maximum value of the first ripple current to the maximum value of the second ripple current is greater than 0 and less than 1.

[0022] Optionally, determining the target coupling coefficient according to the second function relationship, the maximum value of the second ripple current on the discrete inductor, and the preset conditions under the condition that the inverter topology circuit is connected to the discrete inductor includes:

[0023] Determine the coupling coefficient corresponding to the minimum maximum value of the first ripple current as the first coupling coefficient according to the second function relationship;

[0024] When the ratio of the minimum maximum value of the first ripple current to the maximum value of the second ripple current is greater than 0 and less than 1, determine the first coupling coefficient as the target coupling coefficient under the selected connection method.

[0025] Optionally, before determining the first function relationship between the ripple current of the inductor coil, the coupling coefficient of the coupled inductor, and the sine modulation signal for pulse width modulation of the inverter topology circuit according to the connection method of the selected coupled inductor and the inverter topology circuit, it further includes: selecting the connection method of the coupled inductor and the inverter topology circuit;

[0026] Determining the target coupling coefficient according to the second function relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor includes:

[0027] Determine the target coupling coefficient under the selected connection method according to the second function relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor;

[0028] The design method further includes:

[0029] According to the magnitude relationship of the maximum values of the first ripple currents corresponding to each inductor coil under the target coupling coefficients of different connection methods, determine the target connection method and the target coupling coefficient corresponding to the target connection method.

[0030]

[0031] Optionally, after determining the target coupling coefficient according to the second function relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor, it further includes:

[0032] Substitute the target coupling coefficient into the second function relationship to determine the ratio of the maximum value of the first ripple current to the maximum value of the second ripple current;

[0033] Determine the self-inductance value of the inductance coil by multiplying the ratio of the maximum value of the first ripple current to the maximum value of the second ripple current by the self-inductance value of the discrete inductor;

[0034] Determine the mutual inductance value of the coupled inductor according to the self-inductance value of the inductance coil and the target coupling coefficient.

[0035] Optionally, before the maximum value of the second ripple current on the discrete inductor under the condition that the discrete inductor is connected to the inverter topology circuit according to the second function relationship, it further includes:

[0036] Determine the fourth function relationship between the ripple current corresponding to the discrete inductor and the sine modulation signal for pulse width modulation of the inverter topology circuit under the condition that the discrete inductor is connected to the inverter topology circuit;

[0037] Determine the maximum value of the second ripple current according to the fourth function relationship.

[0038] According to another aspect of the present invention, there is provided an inverter capable of split-phase output, characterized in that it includes a coupled inductor, and the coupled inductor is designed by using the design method of the coupled inductor in the inverter capable of split-phase output according to any embodiment of the present invention.

[0039] The technical solution of the embodiment of the present invention obtains the first function relationship by regarding the sine modulation signal of the inverter topology circuit and the coupling coefficient as variables, and analyzes the first function relationship to obtain the second function relationship between the maximum value of the first ripple current and the coupling coefficient when the coupled inductor and the inverter topology circuit are in the selected connection mode. Based on the maximum value of the first ripple current determined by the second function relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the discrete inductor is connected to the inverter topology circuit, the target coupling coefficient that satisfies the maximum value of the first ripple current corresponding to each inductance coil being less than the maximum value of the second ripple current is determined, so that the self-inductance of the coupled inductor can be smaller relative to the inverter with a discrete inductor connected to the inverter topology circuit, and further the volume and weight of the coupled inductor can be smaller, which is beneficial to reducing the core loss.

[0040] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0042] Figure 1It is a schematic structural diagram of an inverter with split-phase output provided by an embodiment of the present invention;

[0043] Figure 2 It is a schematic structural diagram of an inverter topology circuit in the related art;

[0044] Figure 3 It is a flowchart of a method for designing a coupled inductor in an inverter with split-phase output provided by an embodiment of the present invention;

[0045] Figure 4 It is a flowchart of another method for designing a coupled inductor in an inverter with split-phase output provided by an embodiment of the present invention;

[0046] Figure 5 is Figure 1 The modal analysis simulation diagram of the shown inverter;

[0047] Figure 6 It is a schematic structural diagram of another inverter with split-phase output in the related art;

[0048] Figure 7 is Figure 6 The modal analysis simulation diagram of the shown inverter;

[0049] Figure 8 It is a schematic structural diagram of another inverter with split-phase output provided by an embodiment of the present invention;

[0050] Figure 9 It is a flowchart of another method for designing a coupled inductor in an inverter with split-phase output provided by an embodiment of the present invention;

[0051] Figure 10 It is a photovoltaic characteristic curve graph;

[0052] Figure 11 It is a schematic diagram of the simulation result of the inverter topology circuit connected with discrete inductors;

[0053] Figure 12 is an intercept of Figure 11 The schematic diagram of the simulation result at a certain power frequency period;

[0054] Figure 13 It is a schematic diagram of the simulation result of the inverter topology circuit connected with a coupled inductor;

[0055] Figure 14 is an intercept of Figure 14 A schematic diagram of a simulation result at a certain power frequency period;

[0056] Figure 15 is an intercept of Figure 14 Another schematic diagram of the simulation result at a certain power frequency period. Detailed implementation manners

[0057] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0058] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the term "comprising" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0059] The embodiment of the present invention provides a design method for a coupling inductor in an inverter with split-phase output. Figure 1 is a schematic structural diagram of an inverter with split-phase output provided by an embodiment of the present invention. Refer to Figure 1 , the inverter includes an inverter topology circuit 10 and a coupling inductor 20; the inverter topology circuit 10 includes a topology input end and at least two topology output ends, and the inverter topology circuit 10 is used to output a split-phase square wave voltage through the topology output ends according to the input signal at the topology input end; the inverter includes at least two split-phase output ends. Optionally, the topology input end of the inverter topology circuit is connected to a photovoltaic panel. The coupling inductor 20 includes at least two inductor coils, and the inductor coils are connected between the topology output ends of the inverter topology circuit 10 and the split-phase output ends of the inverter. Figure 2 is a schematic structural diagram of an inverter topology circuit in the related art. Figure 2 An optional structure of the inverter topology circuit 10 is exemplarily shown in Figure 2 , the photovoltaic panel PV is connected to the H-bridge full-bridge conversion topology through a capacitor, and the output high-frequency transformer Tra1 is used for boosting. The secondary side of the high-frequency transformer has two windings for output, and each winding output is respectively connected to a set of half-wave conversion circuit topologies to connect to the corresponding topology output ends of the inverter topology circuit 10 ( Figure 1 and Figure 2 exemplarily show the first topology output end A1 and the second topology output end B1), combined with Figure 1 , the voltage output by the inverter topology circuit 10 is connected to the power grid Grid after LC filtering.Figure 1 the second load form 2) or connect the load separately ( Figure 1 the first load form 1) in, and the grid voltage is Vg. The inverter topology circuit 10 can also be any inverter topology circuit 10 in the related art that satisfies split-phase output. The embodiment of the present invention does not limit the specific structure of the inverter topology circuit 10. Combining Figure 1 and Figure 2 , the inverter topology circuit 10 is also connected to the neutral line, and the neutral line is connected to the grounding point n, where the voltage between the split-phase output terminal and the neutral line is the split-phase voltage. Figure 1 and Figure 2 Taking the inverter with split-phase output as a single-phase inverter as an example, a pair of split-phase voltages that the inverter can output are voltages with equal amplitudes and opposite phases.

[0060] Figure 3 is a flowchart of a method for designing a coupling inductor in an inverter with split-phase output provided by an embodiment of the present invention. Referring to Figure 3 , this design method includes:

[0061] S110. According to the connection mode of the selected coupling inductor and the inverter topology circuit, determine the first functional relationship between the ripple current of the inductor coil, the coupling coefficient of the coupling inductor, and the sine modulation signal for pulse width modulation of the inverter topology circuit.

[0062] Among them, considering the symmetry of the split-phase output of the inverter, the self-inductance values of the inductor coils in the coupling inductor 20 should be the same, and the only thing that can be changed in the connection mode of the coupling inductor 20 and the inverter topology circuit 10 is the same-name ends of the inductor coils. Specifically, the connection modes include connecting the same-name ends of the inductor coils to the corresponding topology output terminals respectively, or connecting the same-name ends of the inductor coils to the corresponding split-phase output terminals respectively; or connecting the same-name ends of some inductor coils to the corresponding topology output terminals, or connecting the same-name ends of some inductor coils to the corresponding split-phase output terminals. Exemplarily, for Figure 1 and Figure 2The single-phase inverter shown has an inverter topology circuit 10 including a first topology output terminal A1 and a second topology output terminal B1. The coupled inductor 20 includes a first inductor coil 21 and a second inductor coil 22. The inverter includes a first split-phase output terminal PhaseA and a second split-phase output terminal PhaseB. The connection mode between the coupled inductor 20 and the inverter topology circuit 10 can include four types: The first type is that the same-named terminal of the first inductor coil 21 is connected to the first topology output terminal A1, and the same-named terminal of the second inductor coil 22 is connected to the second topology output terminal B1; the second type is that the same-named terminal of the first inductor coil 21 is connected to the first split-phase output terminal PhaseA, and the same-named terminal of the second inductor coil 22 is connected to the second split-phase output terminal PhaseB; the third type is that the same-named terminal of the first inductor coil 21 is connected to the first topology output terminal A1, and the same-named terminal of the second inductor coil 22 is connected to the second split-phase output terminal PhaseB; the fourth type is that the same-named terminal of the first inductor coil 21 is connected to the first split-phase output terminal PhaseA, and the same-named terminal of the second inductor coil 22 is connected to the second topology output terminal B1. Among them, a first capacitor C is connected between the first split-phase output terminal PhaseA and the neutral line o1 , and a second capacitor C is connected between the second split-phase output terminal PhaseB and the neutral line o2 . Define the current reference direction of the split-phase output of the inverter. For example, taking the direction from the topology output terminal to the split-phase output terminal as the current reference direction. Then, in the first connection mode, the first reference current flows into the same-named terminal of the first inductor coil 21, and the second reference current flows into the same-named terminal of the second inductor coil 22; in the second connection mode, the first reference current flows out of the same-named terminal of the first inductor coil 21, and the second reference current flows out of the same-named terminal of the second inductor coil 22; in the third connection mode, the first reference current flows into the same-named terminal of the first inductor coil 21, and the second reference current flows out of the same-named terminal of the second inductor coil 22; in the fourth connection mode, the first reference current flows out of the same-named terminal of the first inductor coil 21, and the second reference current flows into the same-named terminal of the second inductor coil 22. Thus, the connection method of the coupled inductor 20 is analyzed according to the determined reference directions of voltage and current in the inverter topology circuit 10

[0063] When designing the coupled inductor 20, based on the selected connection mode between the coupled inductor 20 and the inverter topology circuit 10, the ripple current calculation formula of the inductor coil can be determined. This calculation formula can be expressed as the first functional relationship between the ripple current of the inductor coil, the coupling coefficient of the coupled inductor 20, and the sinusoidal modulation signal for pulse width modulation of the inverter topology circuit 10

[0064] S120. Determine the second functional relationship between the maximum value of the first ripple current on the inductor coil and the coupling coefficient of the coupled inductor according to the first functional relationship

[0065] Specifically, in the first functional relationship, the coupling coefficient of the coupled inductor 20 and the sinusoidal modulation signal for pulse width modulation of the inverter topology circuit 10 are regarded as independent variables, and the ripple current of the inductor coil is the dependent variable. To obtain the coupling coefficient of the coupled inductor 20, it is necessary to express the sinusoidal modulation signal in terms of the coupling coefficient. Optionally, based on the first functional relationship, when solving for the maximum value of the ripple current that appears in the inductor coil under the selected connection method, the relationship between the sinusoidal modulation signal and the coupling coefficient is obtained, and then the sinusoidal modulation signal in the first functional relationship is eliminated to obtain the second functional relationship between the maximum value of the first ripple current and the coupling coefficient of the coupled inductor 20. Among them, the maximum value of the first ripple current is the maximum value of the ripple current of the inductor coil when the inverter topology circuit 10 and the coupled inductor 20 are under the selected connection method.

[0066] S130. Determine the target coupling coefficient based on the maximum value of the first ripple current determined according to the second functional relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor; among them, under the target coupling coefficient, the maximum value of the first ripple current corresponding to each inductor coil is less than the maximum value of the corresponding second ripple current.

[0067] Specifically, the second functional relationship is the relationship between the maximum value of the first ripple current and the coupling coefficient. When the coupling coefficient changes, the maximum value of the first ripple current will also change accordingly. In this step, based on the second functional relationship, the maximum value of the first ripple current determined under different set coupling coefficients can be compared with the maximum value of the ripple current on the discrete inductor (i.e., the maximum value of the second ripple current) under the condition that the inverter topology circuit 10 is connected to the discrete inductor. According to the relationship between the maximum value of the first ripple current and the maximum value of the second ripple current on each inductor coil, the target coupling coefficient is obtained. The target coupling coefficient needs to satisfy that under the target coupling coefficient, the maximum value of the first ripple current corresponding to each inductor coil is less than the maximum value of the second ripple current, that is, under the target coupling coefficient, the maximum value of the first ripple current of each inductor coil of the coupled inductor 20 is less than the maximum value of the second ripple current under the condition that the inverter topology circuit 10 is connected to the discrete inductor. In this way, under the same ripple index, the self-inductance of the coupled inductor 20 is reduced relative to the self-inductance of the discrete inductor, so that the volume and weight of the coupled inductor 20 can be reduced relative to the discrete inductor, which is beneficial to reducing the core loss.

[0068] In the design method of the coupled inductor in the inverter with separable phase output of this embodiment, by regarding the sine modulation signal of the inverter topology circuit and the coupling coefficient as variables, a first functional relationship is obtained, and the first functional relationship is analyzed to obtain a second functional relationship between the coupled inductor and the maximum value of the first ripple current and the coupling coefficient under the selected connection mode of the inverter topology circuit. Based on the maximum value of the first ripple current determined by the second functional relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected with discrete inductors, a target coupling coefficient is determined such that the self-inductance of the coupled inductor is smaller than that of the inverter connected with discrete inductors for the inverter topology circuit. Furthermore, the volume and weight of the coupled inductor can be smaller, which is beneficial to reducing the core loss.

[0069] Figure 4 is a flowchart of another design method of the coupled inductor in the inverter with separable phase output provided by the embodiment of the present invention. Refer to Figure 4 , this design method includes:

[0070] S210. Determine the voltage equation of the coupled inductor according to the selected connection mode.

[0071] Among them, the voltage equation of the coupled inductor includes the relationship equation between the inductance voltage on the inductance coil, the current change rate of the inductance coil, the self-inductance value of the inductance coil, and the coupled mutual inductance value.

[0072] Exemplarily, for Figure 1 under the first connection mode shown, the voltage equation of the coupled inductor can be expressed as the following formula (1):

[0073]

[0074] Among them, u Lf1 represents the inductance voltage of the first inductance coil, u Lf2 represents the inductance voltage of the second inductance coil, L f represents the self-inductance value of the inductance coil, M is the coupled mutual inductance value, represents the current change rate on the first inductance coil, represents the current change rate on the second inductance coil.

[0075] S220. Determine a third functional relationship between the current change rate of the inductance coil and the coupling coefficient according to the voltage equation of the coupled inductor.

[0076] Specifically, matrix transformation can be performed on the voltage equation of the coupled inductor to obtain a third functional relationship between the current change rate of the inductance coil and the coupling coefficient. Exemplarily, for Figure 1Under the first connection method shown, through matrix transformation according to formula (1) of the voltage equation of the above-mentioned coupled inductor, the following formula (2) can be obtained:

[0077]

[0078] where M = kL f , where k is the coupling coefficient.

[0079] Optionally, according to the relationship between the output voltage of the topology output terminal and the split-phase voltage, that is, the following formula (3), the difference between the topology output voltage of the topology output terminal and the split-phase voltage output by the split-phase output terminal is used to replace the inductor voltage in the voltage equation to determine the third functional relationship, that is, the following formula (4).

[0080]

[0081] where u an represents the first output voltage between the first topology output terminal and the neutral line, u bn represents the second output voltage between the second topology output terminal and the neutral line, u o1 is the first split-phase voltage output by the inverter, u o2 is the second split-phase voltage output by the inverter.

[0082] S230. Determine the first functional relationship according to the third functional relationship and the relationship between the time when the output voltage of the topology output terminal is not equal to 0 within the power frequency period and the sine modulation signal.

[0083] Figure 5 is Figure 1 the modal analysis simulation diagram of the inverter shown, where Figure 5 shows the carrier wave v saw for pulse width modulation of the inverter topology circuit, the sine reference wave v ref1 and v ref2 , the first output voltage u an , the second output voltage u bn , the inductor voltage u Lf1 of the first inductor coil, the inductor voltage u Lf2 of the second inductor coil, the first split-phase voltage u o1 and the second split-phase voltage u o2 , and the waveforms of the current on the first inductor coil (denoted as the first inductor current i Lf1 ). It should be noted that Figure 5 only the first inductor current i Lf1 within one power frequency period corresponding to the area boxed by the dotted line is shown. It should be noted that Figure 1Under the shown connection mode, the ripple current on the second inductance coil is equal to that on the first inductance coil. Therefore, in this embodiment, only the ripple current on the first inductance coil is analyzed.

[0084] According to Figure 5 it is known that the maximum value of the first ripple current of the first inductance coil is generated during the period when the first output voltage u an is not 0. Therefore, only the period when the first output voltage u an is not 0 needs to be analyzed, and the first functional relationship can be expressed by the following formula (5):

[0085]

[0086] In the case of split-phase output of the inverter, the first output voltage and the second output voltage satisfy the following formula (9):

[0087]

[0088] Accordingly, the first functional relationship can be expressed as the following formula (10):

[0089]

[0090] Among them, T on represents the time when the first output voltage u an is not equal to 0 within a power frequency period; u anmax represents the amplitude of the first output voltage; ω g is the power grid power frequency, f s is the carrier frequency, T s is the carrier period, m is the modulation ratio, is the power factor, represents the sine modulation signal.

[0091] S240. Determine the relationship satisfied between the sine modulation signal and the coupling coefficient when the ripple current is the largest according to the first functional relationship.

[0092] Specifically, in the first functional relationship, the product of the modulation ratio m and the sine modulation signal can be recorded as a variable. For example, let Since the modulation ratio m is greater than 0 and less than 1, is also greater than 0 and less than or equal to 1, then x is a variable that changes between [0-1).

[0093] Let:

[0094]

[0095] Combined with formula (10), formula (11) and The first functional relationship can be expressed by the following formula (12).

[0096]

[0097] It can be seen that the above formula is a quadratic function of one variable and has a unique maximum value. The solution is as follows:

[0098] Taking the differential of formula (12), we can obtain:

[0099]

[0100] Based on this, we can get

[0101]

[0102] Therefore, when the relationship between the sine modulation signal and the coupling coefficient satisfies the above formula (14) according to the first functional relationship, the ripple current is the largest.

[0103] S250. Determine the second functional relationship according to the relationship satisfied between the sine modulation signal and the coupling coefficient, and the first functional relationship.

[0104] Specifically, after obtaining the relationship satisfied between the sine modulation signal and the coupling coefficient, substituting this relationship into the first functional relationship, the second functional relationship can be obtained.

[0105] Exemplarily, substituting formula (14) into formula (12), we can obtain:

[0106]

[0107] where, Δi Lf1max1 represents the maximum value of the first ripple current.

[0108] S260. Determine the target coupling coefficient according to the second functional relationship, the maximum value of the second ripple current on the discrete inductor, and the preset conditions under the condition that the inverter topology circuit is connected to the discrete inductor; wherein, the preset conditions include that the ratio of the maximum value of the first ripple current to the maximum value of the second ripple current is less than 1.

[0109] In this step, the maximum value of the first ripple current under the condition that the inverter topology circuit is connected to the coupled inductor is compared with the maximum value of the second ripple current under the condition that the inverter topology circuit is connected to the discrete inductor. Therefore, it is necessary to obtain the maximum value of the second ripple current. Optionally, in the above embodiments, before S110 and S21O, it may include: determining the fourth functional relationship between the ripple current corresponding to the discrete inductor and the sine modulation signal for pulse width modulation of the inverter topology circuit under the condition that the inverter topology circuit is connected to the discrete inductor; determining the maximum value of the second ripple current according to the fourth functional relationship. Figure 6It is a schematic structural diagram of another inverter with split-phase output in the related art. Refer to Figure 6 , in this inverter, the inverter topology circuit 10 is connected to discrete inductors. Taking the first topology output terminal A1 of the inverter topology circuit 10 connected to the third inductor coil 30 and the second topology output terminal B1 connected to the fourth inductor coil 40 as an example, the third inductor coil 30 and the fourth inductor coil 40 are discrete inductors, and their self-inductance values are equal.

[0110] According to Figure 6 , the second ripple current under the condition that the inverter topology circuit is connected to discrete inductors is analyzed.

[0111] The analysis of the current change value on the discrete inductor is as follows:

[0112]

[0113] represents the current change rate of the third inductor coil 30, represents the current change rate of the fourth inductor coil 40, u Lf3 represents the inductor voltage of the third inductor coil 30, u Lf4 represents the inductor voltage of the fourth inductor coil 40, L f represents the self-inductance of the third inductor coil 30 and also represents the self-inductance of the fourth inductor coil 40.

[0114] Figure 7 is Figure 6 the modal analysis simulation diagram of the shown inverter. One power frequency period is selected in the mode, where Figure 7 shows the carrier wave v for pulse width modulation of the inverter topology circuit saw , the sine reference wave v ref1 and v ref2 , the first output voltage u an , the second output voltage u bn , the inductor voltage u of the third inductor coil 30 Lf3 , the inductor voltage u of the fourth inductor coil 40 Lf4 , the first split-phase voltage u o1 and the second split-phase voltage u o2 , and the waveforms of the current on the third inductor coil 30 (denoted as the first inductor current i Lf3 ). It should be noted that Figure 7 only the first inductor current i corresponding to the power frequency period within the area framed by the dotted line is shown Lf3 .

[0115] According to the topology mode, according to u o1 , u o2 , u an , u bn , and calculate uLf3 , u Lf4 , and finally, the current i of the third inductance coil 30 is calculated through Equation (16). Lf3 The waveform of i Lf3 Here, only two carrier periods are selected for distance analysis. Considering that u o1 =-u o2 =0.5u o , then the fourth functional relationship is:

[0116]

[0117] where m is the modulation ratio, ω g is the power grid power frequency, f s is the carrier frequency, T s is the carrier period, is the power factor, and u o represents the voltage between the first split-phase output terminal and the second split-phase output terminal.

[0118] It is easy to obtain that the maximum value is When it is close to 1, the above formula has the maximum value. Based on this, the maximum value of the second ripple current △i on the third inductance coil 30 can be obtained as: Lf3max It can be expressed as:

[0119]

[0120] According to the preset condition, that is, the ratio of the maximum value of the first ripple current to the maximum value of the second ripple current is less than 1, and combined with the formula (15) of the maximum value of the first ripple current obtained according to the second functional relationship, the ratio p of the maximum value of the first ripple current to the maximum value of the second ripple current is:

[0121]

[0122] According to formula (19), the coupling coefficient that satisfies p greater than 0 and less than 1 is obtained as the target coupling coefficient.

[0123] In some alternative embodiments, the above step 260 includes: according to the second functional relationship, determining the coupling coefficient corresponding to the minimum maximum value of the first ripple current as the first coupling coefficient; when the ratio of the minimum maximum value of the first ripple current to the maximum value of the second ripple current is greater than 0 and less than 1, determining the first coupling coefficient as the target coupling coefficient under the selected connection mode.

[0124] Specifically, for the above formula (15), the denominator is taken as:

[0125] g(k)=(1-k)(k + 1) 2 (20);

[0126] If the maximum value of the denominator is obtained, the maximum value of the first ripple current can be taken as the minimum value. Similarly, taking the derivative:

[0127] g′(k) = -3k 2 -2k + 1 = 0 (21);

[0128] We get:

[0129]

[0130] Among them, when k = k2, it is the maximum value of g(k) within the range of k ∈ [0, 1]. At this time, the maximum value of the first ripple current is the smallest, that is:

[0131]

[0132] At this time, x = 0.75, then the maximum value of the first ripple current is:

[0133]

[0134] It can be seen that when k = 1 / 3, the maximum current ripple of the coupled inductor is 1 / 1.185 of that of the discrete inductor. It can also be considered that under the same ripple index, the self-inductance can be selected as 1 / 1.185 of the original discrete value, that is, the self-inductance is reduced by 15.612%. Considering that the coupled inductor itself is also limited by volume and weight, therefore, according to the design method of the coupled inductor in this embodiment, the volume and weight of the filter inductor can be reduced to a certain extent, and it is beneficial to reduce magnetic loss.

[0135] It should be noted that in this embodiment, the above analysis process analyzes the maximum value of the first ripple current of the inductor coil in the first connection mode between the coupled inductor and the inverter topology circuit, and obtains the target coupling coefficient. In the second connection mode and the first connection mode, the first ripple current of the inductor coil is the same as the maximum value of the first ripple current in the first connection mode, which will not be elaborated here.

[0136] The above analysis process analyzes the target coupling coefficient in the first connection mode. Next, the maximum value of the first ripple current of the inductor coil in the third connection mode between the coupled inductor and the inverter topology circuit will be analyzed. Figure 8 is a schematic structural diagram of another split-phase output inverter provided by an embodiment of the present invention. Refer to Figure 8 , the connection mode between the coupled inductor 20 and the inverter topology circuit 10 in this inverter is the third connection mode.

[0137] In the third connection mode, the coupled voltage equation can be expressed as the following formula (23).

[0138]

[0139] The matrix transformation yields formula (24):

[0140]

[0141] Furthermore, formula (25) can be obtained:

[0142]

[0143] Correspondingly, in the third connection mode, the first functional relationship between the ripple current of the first inductance coil 21, the coupling coefficient of the coupled inductor 20, and the sine modulation signal of the pulse width modulation of the inverter topology circuit 10 is:

[0144]

[0145] It can be obtained that the ripple current of the first inductance coil 21 in the third connection mode is the same as that in the first connection mode, and no further analysis is required. Although the third connection mode does not have complete symmetry, even when the ripple current of the second inductance coil 22 is small, since the ripple current of the first inductance coil 21 is the same as that in the first connection mode, and the self-inductance of the coupled inductor 20 needs to be designed according to the maximum self-inductance value of each inductance coil, the ripple current of the second inductance coil 22 can no longer be analyzed. The analysis process of the fourth connection mode is the same as that of the third connection mode, and will not be elaborated here. In addition, the structural requirements of the split-phase output require that the inductance coils of the coupled inductor 20 also have symmetry to avoid affecting the output current and harmonic content.

[0146] Figure 9 is a flowchart of another method for designing a coupled inductor in a split-phase output inverter provided by an embodiment of the present invention. Refer to Figure 9 , optionally, the method for designing a coupled inductor in a split-phase output inverter includes:

[0147] S310. Select the connection mode of the coupled inductor and the inverter topology circuit.

[0148] Specifically, in this step, one of the four connection modes between the coupled inductor and the inverter topology circuit in the above embodiments can be selected.

[0149] S320. According to the selected connection mode of the coupled inductor and the inverter topology circuit, determine the first functional relationship between the ripple current of the inductance coil, the coupling coefficient of the coupled inductor, and the sine modulation signal of the pulse width modulation of the inverter topology circuit; this step is the same as the process of S110 in the above embodiments and will not be elaborated here.

[0150] S330. Determine the second functional relationship between the maximum value of the first ripple current on the inductance coil and the coupling coefficient of the coupled inductor according to the first functional relationship; this step is the same as the process of S120 in the above embodiment and will not be elaborated here.

[0151] S340. Determine the maximum value of the second ripple current on the discrete inductor under the condition of the maximum value of the first ripple current determined according to the second functional relationship and the discrete inductor being connected to the inverter topology circuit, and determine the target coupling coefficient for the selected connection method.

[0152] In this step, to determine the target coupling coefficient for the selected connection method, the method for determining the target coupling coefficient in step 260 above can be adopted and will not be elaborated here.

[0153] S350. Determine the target connection method and the target coupling coefficient corresponding to the target connection method according to the magnitude relationship of the maximum values of the first ripple currents corresponding to each inductance coil under the target coupling coefficients of different connection methods.

[0154] Specifically, in this embodiment, the target connection method can be determined according to the magnitude relationship of the maximum values of the first ripple currents corresponding to the inductance coils connected to the same topology output end of the inverter circuit under the target coupling coefficients of different connection methods. Among them, under the target connection method, the maximum value of the first ripple current on the inductance coil connected to each topology output end is smaller than the maximum value of the first ripple current on the inductance coil connected to the corresponding topology output end under other connection methods.

[0155] In this embodiment, by comparing the maximum values of the first ripple currents of each inductance coil under the target coupling coefficients of different connection methods, the target connection method with the minimum maximum value of the first ripple current can be obtained, so that the self-inductance of the coupled inductor can be reduced more relative to the discrete inductor, further reducing the volume and weight of the coupled inductor.

[0156] Based on the above embodiments, optionally, after S130, S260, and S350, it further includes: substituting the target coupling coefficient into the second functional relationship to determine the ratio of the maximum value of the first ripple current to the maximum value of the second ripple current; multiplying the ratio of the maximum value of the first ripple current to the maximum value of the second ripple current by the self-inductance value of the discrete inductor to determine the self-inductance value of the inductance coil; determining the mutual inductance value of the coupled inductor according to the self-inductance value of the inductance coil and the target coupling coefficient.

[0157] Specifically, for an inverter that connects discrete inductors based on an inverter topology circuit, if the self-inductance value of the discrete inductor is known, the self-inductance value of the inductor coil and the mutual inductance value of the coupled inductor can be determined based on the known self-inductance value of the discrete inductor and the product of the ratio of the maximum value of the first ripple current to the maximum value of the second ripple current under the target coupling coefficient, thereby realizing the parameter design of the coupled inductor.

[0158] The design method of the coupled inductor in the above embodiments of the present invention can quantitatively calculate the coupling coefficient, and is applicable to single-phase separable voltage source inverters and can theoretically reduce the self-inductance by about 15.6% compared with discrete inductors, reduce the weight and volume of the filter inductors of the voltage source inverter, and improve the power density. The proposed design method of the coupled inductor analyzes through the inductor voltage mode after coupling, so that only the current fluctuation value when the split-phase voltage part is not zero needs to be analyzed. When analyzing the maximum ripple current, the proposed design method of the coupled inductor regards the sine modulation signal and the coupling coefficient as variables for function analysis. The proposed design method of the coupled inductor is independent of the phase difference between voltage and current and is applicable to inverters with reactive power support.

[0159] An embodiment of the present invention also provides a separable output inverter, combined with Figure 1 , the inverter includes a coupled inductor 20, and the coupled inductor 20 is designed by using the design method of the coupled inductor in any of the above embodiments of the present invention for the separable output inverter, and has the beneficial effects of the separable output inverter in any of the above embodiments of the present invention, which will not be elaborated here. The inverter further includes an inverter topology circuit 10, the inverter topology circuit includes a topology input end and at least two topology output ends, and the inverter topology circuit is used to output a split-phase square wave voltage through the topology output end according to the input signal at the topology input end. Specifically, the inverter topology circuit 10 can output a split-phase square wave voltage after pulse width modulation. The separable output inverter of the embodiment of the present invention can be applied to new energy power generation fields such as photovoltaic power generation systems.

[0160] In specific implementation, a micro photovoltaic inverter is used for simulation verification. The maximum output power of the micro photovoltaic inverter is 600W, the input voltage Vpv is 22 - 55V, and the grid voltage Vg is 240Vac ± 10%.

[0161] The above design method is simulated and verified in simulation software. The selected photovoltaic parameters are shown in Table 1.

[0162] Table 1 Photovoltaic parameters used in simulation (illumination 1000W / m^2, temperature 25°C)

[0163]

[0164] Correspondingly,Figure 10 It is a photovoltaic characteristic curve graph.

[0165] Figure 10 It is the output waveforms when the light intensity is 1000 W / m² and the temperature is 25°C, and the photovoltaic voltage reference values are 22 V and 55 V. Among them, the abscissa U is the voltage with the unit of V; the ordinates are the current and power respectively, and the units are A and W respectively.

[0166] The following analyzes two working conditions where the inverter topology circuit is connected with a discrete inductor and a coupled inductor respectively.

[0167] Condition 1: Connection method of discrete filter inductor

[0168] Figure 11 It is a schematic diagram of the simulation result when the inverter topology circuit is connected with a discrete inductor. Figure 12 It is an intercepted Figure 11 Schematic diagram of the simulation result under a certain power frequency cycle. Combining Figure 6 、 Figure 11 and Figure 12 , Figure 11 and Figure 12 show the waveforms of the first split-phase output voltage u o1 and the second split-phase output voltage u o2 , the voltage between the first topology output terminal and the neutral line is u ab1 and the voltage between the second topology output terminal and the neutral line is u ab2 , the waveform of the third inductor current i Lf3 of the third inductor coil 30 and the waveform of the fourth inductor current i Lf4 of the fourth inductor coil 40, the waveform of the sinusoidal modulation signal, the waveform of the third inductor voltage u Lf3 of the third line inductor coil and the waveform of the fourth inductor voltage u Lf4 of the fourth inductor coil 40, and the grid-connected current i g . In this simulation, the self-inductance L f of the inductor coil is uniformly used as 3.6 mH, and the capacitance C f is 3.3 μF. In addition, in the simulation, u ab1 , u ab2 is equivalent to u an , u bn of this patent.

[0169] According to the simulation results, the waveforms of the voltages and currents of the third inductor coil 30 and the fourth inductor coil 40 are in agreement with the theoretical analysis. The ripple analysis is as follows:

[0170] According to formula (18), and f s = 100 kHz, it can be known that the theoretical maximum ripple can be obtained when the sinusoidal modulation signal is 1:

[0171]

[0172] According to Figure 12 , the simulation result is 0.5166 A. Considering the error of the simulation step size and the fact that the sine modulation signal does not reach 1, they are basically in agreement.

[0173] Condition 2: Connection method of the coupled filter inductor

[0174] Figure 13 It is a schematic diagram of the simulation result of the inverter topology circuit connected to the coupled inductor. Figure 14 It is intercepted Figure 13 A schematic diagram of a simulation result under a certain power frequency cycle. Figure 15 It is intercepted Figure 13 Another schematic diagram of the simulation result under a certain power frequency cycle. Combining Figure 1 , Figure 14 and Figure 15 , Figure 14 and Figure 15 show the first split-phase output voltage u o1 and the second split-phase output voltage u o2 . The voltage between the first topology output terminal and the neutral line is u ab1 and the voltage between the second topology output terminal and the neutral line is u ab2 . The waveform of the first inductor current i Lf1 of the first inductor coil and the waveform of the second inductor current i Lf2 of the second inductor coil, the waveform of the sine modulation signal, the waveform of the first inductor voltage u Lf1 of the first inductor coil and the waveform of the second inductor voltage u Lf2 of the second inductor coil, and the grid-connected current i g . In this simulation, the self-inductance L f = 3.6 mH of the inductor coil is uniformly used, and the capacitance C f = 3.3 uF. In addition, in the simulation, u ab1 , u ab2 is equivalent to u an of this patent, and u bn .

[0175] According to the previous analysis, under the condition that the inverter topology circuit is connected to the coupled self-inductance, when is close to 1, the maximum value of the current ripple cannot be obtained. In the figure, 12 obtains the situation of .

[0176] Theoretical calculation shows that:

[0177]

[0178] Combining Figure 14 , the simulation result is 0.41813 A, and the two are basically in agreement.

[0179] According to the analysis process of the above embodiments of the present invention, when the target coupling coefficient k = 1 / 3, the maximum value of the first ripple current is minimized. In this case 15 in the figure reaches the situation, it can be obtained that the minimum value of the maximum value of the first ripple current is:

[0180]

[0181] Combined with Figure 15 , the simulation is 0.43575A, which is basically consistent. Thus, it can be verified that the design method of the coupled inductor in the above embodiments of the present invention is correct.

[0182] It should be understood that various forms of the processes shown above can be used, reordering, adding, or deleting steps. For example, the steps recited in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is made herein.

[0183] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for designing a coupled inductor in an inverter capable of splitting phase output, characterized in that: The inverter comprises an inverter topology circuit and a coupled inductor; the inverter topology circuit comprises a topology input terminal and at least two topology output terminals, and the inverter topology circuit is used to output a split-phase square wave voltage through the topology output terminal according to an input signal of the topology input terminal; the inverter comprises at least two split-phase output terminals; The coupled inductor comprises at least two inductance coils, and the inductance coils are connected between the topology output terminal and the phase-splitting output terminal; The design method comprises: According to the selected connection mode of the coupled inductor and the inverter topology circuit, a first functional relationship between the ripple current of the inductor coil and the coupling coefficient of the coupled inductor and the sinusoidal modulation signal for pulse width modulation of the inverter topology circuit is determined; the connection mode includes connecting the same-name ends of each of the inductor coils to the corresponding topology output end, or to the corresponding split-phase output end; or connecting the same-name ends of some of the inductor coils to the corresponding topology output end, or connecting the same-name ends of some of the inductor coils to the corresponding split-phase output end; Determine a second functional relationship between a maximum value of a first ripple current on the inductor and a coupling coefficient of the coupling inductor according to the first functional relationship; The target coupling coefficient is determined according to the maximum value of the first ripple current determined by the second functional relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor; wherein, under the target coupling coefficient, the maximum value of the first ripple current corresponding to each of the inductor coils is less than the corresponding maximum value of the second ripple current; the first functional relationship between the ripple current of the inductor coil and the coupling coefficient of the coupled inductor and the sinusoidal modulation signal for pulse width modulation of the inverter topology circuit is determined according to the selected connection mode of the coupled inductor and the inverter topology circuit, including: Determine the voltage equation of the coupled inductor according to the selected connection mode; the voltage equation of the coupled inductor includes a relationship equation between the inductor voltage on the inductor coil and the current change rate of the inductor coil, the self-inductance value of the inductor coil, and the coupled mutual inductance value; Determining a third functional relationship between the current change rate of the inductor coil and the coupling coefficient according to the voltage equation of the coupled inductor; The first functional relationship is determined according to the third functional relationship and the relationship between the time during which the output voltage of the topology output terminal is not equal to 0 and the sinusoidal modulation signal within the power frequency cycle.

2. The design method according to claim 1, characterized in that: Determining the third functional relationship between the current change rate of the inductor and the coupling coefficient according to the voltage equation includes: The third functional relationship is determined by using a difference between a topological output voltage at the topological output terminal and a split-phase voltage outputted by the split-phase output terminal to replace the inductor voltage in the voltage equation.

3. The design method according to claim 1, characterized in that: The determining, according to the first functional relationship, a second functional relationship between the maximum value of the first ripple current on the inductor and the coupling coefficient of the coupling inductor comprises: Determine, according to the first functional relationship, a relationship satisfied between the sinusoidal modulation signal and the coupling coefficient when the ripple current is maximum; The second functional relationship is determined according to the relationship satisfied between the sinusoidal modulation signal and the coupling coefficient, and the first functional relationship.

4. The design method according to claim 1, characterized in that: The determining of the target coupling coefficient according to the second functional relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor includes: The target coupling coefficient is determined based on the second functional relationship and the second ripple current maximum value on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor and the preset condition; wherein the preset condition includes that the ratio of the first ripple current maximum value to the second ripple current maximum value is greater than 0 and less than 1.

5. The design method according to claim 4, characterized in that: The determining of the target coupling coefficient according to the second functional relationship and the second ripple current maximum value on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor and the preset condition includes: According to the second functional relationship, determining the coupling coefficient corresponding to the minimum maximum value of the first ripple current as the first coupling coefficient; When the ratio of the minimum first ripple current maximum value to the second ripple current maximum value is greater than 0 and less than 1, the first coupling coefficient is determined as the target coupling coefficient under the selected connection mode.

6. The design method according to claim 1, characterized in that: Before determining the first functional relationship between the ripple current of the inductor coil and the coupling coefficient of the coupling inductor and the sinusoidal modulation signal for pulse width modulation of the inverter topology circuit according to the selected connection mode of the coupling inductor and the inverter topology circuit, the method further includes: selecting the connection mode of the coupling inductor and the inverter topology circuit; The determining of the target coupling coefficient according to the second functional relationship and the maximum value of the second ripple current on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor includes: Determining the target coupling coefficient under the selected connection mode according to the second functional relationship and the second ripple current maximum value on the discrete inductor under the condition that the inverter topology circuit is connected to the discrete inductor; The design method further comprises: According to the magnitude relationship between the maximum values ​​of the first ripple current corresponding to each of the inductor coils under the target coupling coefficients of the different connection modes, a target connection mode and the target coupling coefficient corresponding to the target connection mode are determined.

7. The design method according to claim 1, characterized in that: After determining the target coupling coefficient according to the second functional relationship and the condition that the inverter topology circuit is connected to the discrete inductor, the second ripple current maximum value on the discrete inductor is determined, the method further includes: Substituting the target coupling coefficient into the second functional relationship to determine a ratio of the first ripple current maximum value to the second ripple current maximum value; Determine the self-inductance of the inductor coil by multiplying the ratio of the first ripple current maximum value to the second ripple current maximum value by the self-inductance of the discrete inductor; The mutual inductance value of the coupled inductor is determined according to the self-inductance value of the inductor coil and the target coupling coefficient.

8. The design method according to claim 1, characterized in that: Under the condition that the discrete inductor is connected according to the second functional relationship and the inverter topology circuit, before the second ripple current maximum value on the discrete inductor is reached, the method further includes: Determine a fourth functional relationship between a ripple current corresponding to the discrete inductor and a sinusoidal modulation signal for pulse width modulation of the inverter topology circuit under the condition that the inverter topology circuit is connected to the discrete inductor; The second ripple current maximum value is determined according to the fourth functional relationship.

9. An inverter capable of split-phase output, characterized in that: It comprises a coupled inductor, and the coupled inductor is designed by using the coupled inductor design method in an inverter capable of split-phase output according to any one of claims 1 to 8.

Images