Method, device and equipment for determining inductance of filter inductor and medium

Abstract

The invention discloses a method, a device and equipment for determining the inductance of a filter inductor and a medium, and relates to the technical field of inverters. By establishing a target state equation, the dynamic change of the output voltage under different bridge arms of the inverter system and the current of the filter inductor can be known subsequently. And according to the target state equation, determining a branch current of a coupling inductance winding of each bridge arm and a target current corresponding to filtering, so that the branch current and the target current are abstracted into a mathematical expression in a circuit operation process, and the branch current and the target current are deduced and determined through a mathematical mode. And determining the ripple current variation of the filter inductor by taking the determined branch current and the target current as subsequent constraint parameters. Furthermore, the inductance value of the filter inductor is determined based on the ripple current variable quantity of the filter inductor, and is used as an important basis for selecting the filter inductor, so that the specific inductance value is determined on the basis of reducing the inductance value of the filter inductor, and the selection accuracy is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inverters, in particular to a method and device for determining the inductance of a filter inductor, equipment and a medium. BACKGROUND

[0002] In the field of photovoltaic and energy storage technology, traditional three-level system technology is becoming mature. The power of a single photovoltaic inverter or a single energy storage converter corresponding to a single power bridge arm increases, and the output current of the converter also increases. In order to keep the current ripple within an acceptable range, a larger inductance filter inductor is needed to provide sufficient current smoothing capability. The larger the inductance, the larger the space occupied by the filter inductor and the higher the system cost.

[0003] Therefore, how to reduce the inductance of the filter inductor in a high-power inverter system to reduce the occupied space and system cost of the filter inductor is an urgent problem for those skilled in the art. SUMMARY

[0004] The purpose of the present application is to provide a method and device for determining the inductance of a filter inductor, equipment and a medium to solve the problem of high cost and large space occupied by the filter inductor with large inductance in a conventional power inverter system.

[0005] To solve the above technical problems, the present application provides a method for determining the inductance of a filter inductor, which is applied to a multi-level inverter system, the multi-level inverter system comprising a coupling inductor, a filter inductor and at least two bridge arms in parallel connection; the output ends of the at least two bridge arms are connected to the coupling inductor, and the coupling inductor is connected to the filter inductor; the modulation waves of the at least two bridge arms are out of phase by 180°, and the method comprises:

[0006] establishing a target state equation between the coupling inductor corresponding to each bridge arm, the filter inductor and the grid voltage;

[0007] determining the branch current of the coupling inductor output winding of each bridge arm and the target current of the filter inductor according to the target state equation;

[0008] determining the ripple current variation of the filter inductor according to the branch current and the target current;

[0009] determining the inductance of the filter inductor based on the ripple current variation of the filter inductor.

[0010] On the one hand, the establishment of a target state equation between the coupling inductor corresponding to each bridge arm, the filter inductor and the grid voltage comprises:

[0011] establishing a first voltage formula of the coupling inductance corresponding to each bridge arm between a self-inductance coefficient of the coupling inductance, a mutual inductance coefficient of the coupling inductance and a change rate of the current of each bridge arm;

[0012] establishing a second voltage formula of the filter inductance between the unknown inductance parameter of the filter inductance and the sum of the current values of each bridge arm;

[0013] establishing a relationship formula between each bridge arm, the unknown inductance parameter of the filter inductance and the grid voltage;

[0014] taking the first voltage formula, the second voltage formula and the relationship formula as the target state equation.

[0015] On the other hand, determining the branch current of the coupling inductance output winding of each bridge arm and the target current of the filter inductance according to the target state equation, comprising:

[0016] converting the target state equation into an S-domain equation;

[0017] obtaining a first equation by Laplace transform on the S-domain equation;

[0018] determining the initial state quantity of the first equation as 0 in the steady state of the multi-level inverter system;

[0019] determining the branch current and the target current of the filter inductance according to the first equation constructed after the steady state.

[0020] On the other hand, determining the ripple current change amount of the filter inductance according to the branch current and the target current, comprising:

[0021] determining a second equation corresponding to the current change amount of the branch current and the target current by inverse Laplace transform on the first equation corresponding to the branch current and the target current;

[0022] when the mutual inductance coefficient of the coupling inductance is equal to the self-inductance coefficient, simplifying the equation corresponding to the current change amount of the target current in the second equation to obtain the ripple current change amount of the filter inductance.

[0023] On the other hand, after determining the second equation, the method further comprises:

[0024] determining a circulating current equation corresponding to each bridge arm according to the equation of each branch current in the second equation;

[0025] when the mutual inductance coefficient of the coupling inductance is equal to the self-inductance coefficient, simplifying the circulating current equation to obtain a third equation;

[0026] determining the self-inductance value of the coupling inductance based on the third equation.

[0027] In another aspect, determining the inductance of the filter inductor based on the change in the ripple current of the filter inductor comprises:

[0028] obtaining a first relationship between the output voltage duty cycle of the multi-level inverter system and the grid voltage;

[0029] obtaining a second relationship of the corresponding first relationship and time variation at the current peak;

[0030] determining the inductance of the filter inductor according to the first relationship, the second relationship, and the change in the ripple current of the filter inductor.

[0031] In another aspect, after determining the inductance of the filter inductor, the method further comprises:

[0032] obtaining a first inductance of the filter inductor determined by the multi-level inverter system in a preset manner;

[0033] determining a first ratio according to the inductance of the filter inductor and the first inductance;

[0034] if the first ratio is less than 1, selecting a corresponding filter inductor device according to the inductance of the filter inductor.

[0035] To solve the above technical problems, the present application further provides a filter inductor inductance determination device applied to a multi-level inverter system, the multi-level inverter system comprising a coupling inductor, a filter inductor, and at least two bridge arms in parallel; the output ends of the at least two bridge arms are connected to the coupling inductor, and the coupling inductor is connected to the filter inductor; the modulation waves of the at least two bridge arms are out of phase by 180°, and the device comprises:

[0036] a building module for building a target state equation between the corresponding coupling inductor, the filter inductor, and the grid voltage of each bridge arm;

[0037] a first determination module for determining the branch current of the coupling inductor output winding of each bridge arm and the target current of the filter inductor according to the target state equation;

[0038] a second determination module for determining the change in the ripple current of the filter inductor according to the branch current and the target current;

[0039] a third determination module for determining the inductance of the filter inductor based on the change in the ripple current of the filter inductor.

[0040] To solve the above technical problems, the present application further provides an electronic device comprising a memory for storing a computer program;

[0041] A processor is configured to implement the steps of the method for determining the inductance of a filter inductor when the computer program is executed.

[0042] To solve the above technical problems, the application further provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program is configured to implement the steps of the method for determining the inductance of a filter inductor when executed by a processor.

[0043] The application provides a method for determining the inductance of a filter inductor, which is applied to a multi-level inverter system. The output end of a bridge arm of the multi-level inverter system is connected to a coupling inductor, and the coupling inductor is connected to a filter inductor. The modulation waves of at least two bridge arms are 180 degrees out of phase. The combination of the structure of the inverter system and the carrier interleaving technology of the modulation waves of the bridge arms 180 degrees out of phase reduces the inductance of the filter inductor, reduces the occupied space and reduces the system cost. Furthermore, in the structure, the inductance determination method of the filter inductor is established by establishing a target state equation, so as to know the dynamic changes of the output voltage of the inverter system under different bridge arms and the current of the filter inductor. According to the target state equation, the branch current of the coupling inductor winding of each bridge arm and the corresponding target current of the filter are determined, so as to be abstracted into a mathematical expression during the operation of the circuit, and the branch current and the target current are determined by mathematical derivation. The ripple current variation of the filter inductor is determined by taking the determined branch current and target current as the subsequent constraint parameters. Furthermore, the inductance of the filter inductor is determined based on the ripple current variation of the filter inductor, which is an important basis for selecting the filter inductor, so as to determine the specific inductance on the basis of reducing the inductance of the filter inductor and improve the accuracy of selection.

[0044] In addition, the application further provides a filter inductor inductance determination device, electronic equipment and medium, which have the same beneficial effects as the filter inductor inductance determination method. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0046] Figure 1 A flowchart of a filter inductor inductance determination method provided by the embodiments of the application is provided.

[0047] Figure 2 A structure diagram of a single-phase multi-level inverter system with two bridge arms in parallel is provided for the embodiments of the application.

[0048] Figure 3A structural schematic diagram of a single-phase multi-level inverter system with more than two bridge arms in parallel is provided for an embodiment of the present application.

[0049] Figure 4 A structural schematic diagram of a three-phase multi-level inverter system is provided for an embodiment of the present application.

[0050] Figure 5 A carrier and modulation wave schematic diagram corresponding to the first switch tube and the fourth switch tube under the bridge arm A is provided for an embodiment of the present application.

[0051] Figure 6 A carrier and modulation wave schematic diagram corresponding to the fifth switch tube and the eighth switch tube under the bridge arm B is provided for an embodiment of the present application.

[0052] Figure 7 A coupled winding branch current schematic diagram corresponding to the two bridge arms at two time instants is provided for an embodiment of the present application.

[0053] Figure 8 A state equation setting schematic diagram under the two bridge arms is provided for an embodiment of the present application.

[0054] Figure 9 A structural schematic diagram of a single-phase multi-level inverter system with two bridge arms in parallel under a circulating current path is provided for an embodiment of the present application.

[0055] Figure 10 A simulation schematic diagram of a coupled inductor staggered parallel three-level staggered underlay is provided for an embodiment of the present application.

[0056] Figure 11 A detail expansion diagram based on Figure 10 is provided for an embodiment of the present application.

[0057] Figure 12 A simulation schematic diagram of a coupled inductor maximum ripple current is provided for an embodiment of the present application.

[0058] Figure 13 A structural diagram of a filter inductance inductance determination device is provided for an embodiment of the present application.

[0059] Figure 14 A structural diagram of an electronic device is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0060] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0061] The core of the present application is to provide a filter inductance determination method, device, equipment and medium, to solve the problem of high cost and large space occupied by the large inductance of the filter inductance in the conventional power inverter system.

[0062] In order to make the person in the art better understand the present application scheme, the present application is further described in detail below in combination with the drawings and specific embodiments.

[0063] The power of the conventional three-level system single photovoltaic inverter or energy storage converter is getting larger and larger, the required converter output current is getting larger and larger, and the single power topology needs to handle larger power requirements, the power module needs larger packaging and larger filter inductance, which makes the system cost higher. The multi-level inverter system provided by the present application makes the inverter topology parallel, when the carrier wave of the inverter topology is staggered, the working frequency of the filter inductance of the overall inverter output is 2 times the switching frequency of the power tube, which is beneficial to reduce the size and weight of the filter inductance of the inverter topology output, and reduces the system cost. However, in the design process, the inductance value of the filter inductance is specific, and the inductance determination method of the filter inductance provided by the present application can solve the above technical problems.

[0064] Figure 1 A flow chart of a filter inductance determination method provided by an embodiment of the present application is shown in Figure 1 The method is applied to a multi-level inverter system, the multi-level inverter system includes a coupling inductance, a filter inductance and at least two bridge arms in parallel relationship; the output ends of the at least two bridge arms are connected to the coupling inductance, and the coupling inductance is connected to the filter inductance; the modulation waves of the at least two bridge arms are out of phase by 180°, and the method includes:

[0065] S11: establishing a target state equation between the coupling inductance, the filter inductance and the grid voltage corresponding to each bridge arm;

[0066] S12: determining the branch current of the coupling inductance output winding of each bridge arm and the target current of the filter inductance according to the target state equation;

[0067] S13: determining the ripple current variation of the filter inductance according to the branch current and the target current;

[0068] S14: determining the inductance of the filter inductance based on the ripple current variation of the filter inductance.

[0069] Specifically, Figure 2 A structure diagram of a single-phase multi-level inverter system with two bridge arms in parallel is provided for an embodiment of the present application, Figure 2As shown, the multi-level inverter system includes a coupling inductor, a filter inductor and at least two bridge arms in parallel. The output end of the bridge arm is connected to the coupling inductor, and the coupling inductor is further connected to the filter inductor. The coupling inductor enables the current between the at least two bridge arms to be mutually compensated, reducing the amount of current change that each bridge arm needs to handle, which means that the filter inductor of each bridge arm can be reduced. Through the carrier interleaving technology of the modulation waves of the bridge arms with a phase difference of 180°, the ripple current of the output current is reduced. While achieving the reduction of the inductance of the filter inductor, the occupied space is reduced and the system cost is reduced. Figure 3 A structural diagram of a single-phase multi-level inverter system with more than two bridge arms in parallel is provided for an embodiment of the present application, as shown in Figure 3 As shown, a coupling inductor is connected to the output end of each two bridge arms in parallel, and all the coupling inductors are connected to the same filter inductor.

[0070] Based on this structure, taking two bridge arms in parallel as an example, Figure 2 The structure corresponding to the dashed box in is that the DC+ side, the DC- side and the DCN side of the A bridge arm and the B bridge arm are connected in parallel, and the bridge arm outputs of the two bridge arms are connected to the two input windings of the coupling inductor Lcouple. The output windings of Lcouple are connected in parallel and then connected to the filter inductor Lfilter in series. The two are connected in series, and the connection point of the two is connected to the filter capacitor Cfilter. The other end of the filter capacitor Cfilter is connected to the DCN. The other end of the filter capacitor Cfilter is connected to the DCN. The other end of the filter capacitor Cfilter is connected to the DCN. Figure 4 A structural diagram of a three-phase multi-level inverter system is provided for an embodiment of the present application, as shown in Figure 4 As shown, there are three groups of AB modules and Lcouple, , which constitute a three-phase inverter circuit. The inverter output AC filter circuit is composed of and, which realizes the overall AC output current as a power frequency sine wave current output.

[0071] In the 180° phase difference of the modulation waves of the two bridge arms, the modulation waves of the output currents of the two bridge arms in parallel are the same, and the power frequency phases are the same, Figure 5 A carrier and modulation wave diagram corresponding to the first switch tube and the fourth switch tube under the bridge arm A is provided for an embodiment of the present application, as shown in Figure 5 As shown, the phase shift is viewed as a triangular wave, and the modulation wave is a sine line. If the sine line is greater than the triangular wave, it is determined that the corresponding PWM wave output is high. Figure 6 ​​​A schematic diagram of the carrier and modulation waves corresponding to the fifth and eighth switches under bridge arm B is provided for an embodiment of the present invention, as shown below. Figure 6 As shown, if the sine wave is greater than the triangular wave, the corresponding PWM wave output is high. Combined with... Figure 5 and Figure 6 Notice that the first switch in bridge arm A and the fifth switch in bridge arm B have their respective carriers, carry1 and carry3, phase-shifted by 180°. Similarly, the fourth switch in bridge arm A and the eighth switch in bridge arm B have their respective carriers, carry2 and carry4, phase-shifted by 180°. The modulated wave and carriers intersect, generating PWM waves for the first and fourth switches in bridge arm A, and for the fifth and eighth switches in bridge arm B, based on the area equivalence principle and natural sampling. The PWM waves of the second and third switches in bridge arm A are complementary to the PWM waves of the fourth and first switches in their respective modules, respectively. The relationship between the switches in bridge arm B is similar. Considering the risk of simultaneous switching, a dead time is inserted between the complementary switches.

[0072] because The inductance is small, and its voltage drop is low; for ease of calculation, it is negligible. The impact on high-frequency computing, i.e., the effect of filter capacitors voltage on equal to grid voltage . Figure 7 This invention provides a schematic diagram of the coupled winding branch currents of two bridge arms at two different times, as shown in the embodiment of the invention. Figure 7 As shown, during the period t1-t2, the output state of bridge arm A is P, and the output state of bridge arm B is O. Analysis is performed during this period; the bus voltage is defined as... The voltage across the coupling inductor of bridge arm A is The current in the coupled winding branch is The voltage across the coupling inductor of bridge arm B is The current in the coupled winding branch is ; Filter inductor The voltage across the terminals is Combining Figure 7 Let's look at the bus voltage. The voltage marked between DC+ and DC- in the diagram represents the DC power input for the entire circuit. The voltage across the coupling inductor of bridge arm A is also shown. This is the voltage across the coupled inductor of the Lcoupler, specifically the voltage between one end of the inductor (connected to point P) and the other end (connected to point O). The coupled winding branch current. , is the current flowing through the coupled inductor Lcouple, which flows from point P to point O. The voltage across the coupled inductor of bridge arm B. , is the voltage across the coupled inductor Lcouple. The current in the coupled winding branch. This is the current flowing through the coupling inductor Lcouple, from point P to point O. Since both bridge arms share the same coupling inductor, it is actually the same current, only the setting is for different bridge arms and different times. (Filter inductor) voltage across the two ends It is a filter inductor. The voltage across the two ends of the inductor is the voltage between one end (connected to point O) and the other end (connected to the AC side).

[0073] Step S11 establishes the target state equations relating the coupled inductors, filter inductors, and mains voltage for each bridge arm. This is achieved by combining Kirchhoff's voltage and current laws. By combining Kirchhoff's laws with the characteristics of inductors, a precise dynamic model of the circuit can be established. This model accurately describes the interaction between the coupled inductors, filter inductors, and mains voltage, providing a theoretical basis for circuit design and optimization. Based on the established state equations, circuit parameters (such as inductance, capacitance, and resistance values) can be optimized. By adjusting these parameters, circuit performance can be improved, such as enhancing filtering effectiveness, reducing voltage fluctuations, and improving the power factor.

[0074] In some embodiments, establishing the target state equations between the coupling inductance, filter inductance, and grid voltage corresponding to each bridge arm includes:

[0075] Establish the first voltage formula for each bridge arm corresponding to the coupled inductor, relating the self-inductance coefficient, mutual inductance coefficient, and rate of change of current in each bridge arm.

[0076] Establish a second voltage formula for the filter inductor between the unknown inductance parameters of the filter inductor and the sum of the current values ​​of each bridge arm;

[0077] Establish the relationship formula between the unknown inductance parameters of each bridge arm and filter inductor and the grid voltage;

[0078] The first voltage formula, the second voltage formula, and the relational formula are used as the target state equations.

[0079] Specifically, taking two bridge arms as an example, Figure 8 This is a schematic diagram illustrating the state equation setting under two bridge arms, as provided in an embodiment of the present invention. Figure 8 As shown, the first voltage formula includes the formula for bridge arm A corresponding to the coupled inductor and the formula for bridge arm B corresponding to the coupled inductor. The specific formula for bridge arm A corresponding to the coupled inductor is as follows:

[0080] (1);

[0081] in, Let be the voltage across the coupled inductor in bridge arm A. Let be the self-inductance coefficient of the coupled inductor. For coupling winding branch current The rate of change of current Rate of change over time; is the mutual inductance coefficient of the coupled inductors, representing the effect of current changes between inductors on the coupling of the inductors. For coupling winding branch current The rate of change of current Rate of change over time.

[0082] Similarly, the formula for the coupling inductance corresponding to bridge arm B is as follows:

[0083] (2);

[0084] in, This is the voltage across the coupled inductor in bridge arm B.

[0085] In establishing the second voltage formula, the unknown inductance parameter of the filter inductor is a parameter that needs to be calculated. The sum of the current values ​​of each bridge arm is the rate of change of the total current flowing through the filter inductor in all bridge arms. Based on these two values, taking two bridge arms as an example, the corresponding specific formula is as follows:

[0086] (3);

[0087] in, For the unknown inductance parameters of the filter inductor, This is the voltage across the filter inductor;

[0088] Establish the relationship formulas between the unknown inductance parameters of each bridge arm and the filter inductor and the mains voltage. The relationship formula for bridge arm A is as follows:

[0089] (4);

[0090] in, DC bus voltage Half of Let be the voltage across the coupled inductor in bridge arm A. This is the voltage under the second voltage formula. This is the grid voltage.

[0091] The relationship formula corresponding to bridge arm B is as follows:

[0092] (5);

[0093] in, This is the voltage across the coupled inductor in bridge arm B.

[0094] The first voltage formula, the second voltage formula and the corresponding relationship formula established above are all target state equations.

[0095] The process of establishing state equations by Kirchhoff's voltage law and current law provided by the embodiment describes the relationship between the voltage and current of different parts in the circuit, especially the role of the filter inductor in the circuit. Through these formulas, it is convenient to analyze and calculate the voltage and current of each part in the circuit, so as to further analyze the operation of the whole circuit.

[0096] In step S12, the branch currents of the coupled inductor output windings of each bridge arm and the target current of the filter inductor are determined according to the target state equation, the target state equation is converted into an algebraic equation for solving each current, and the time domain equation is transformed by Laplace transform to simplify the analysis and calculation of the circuit.

[0097] In some embodiments, determining the branch currents of the coupled inductor output windings of each bridge arm and the target current of the filter inductor according to the target state equation comprises:

[0098] Converting the target state equation into an S-domain equation;

[0099] Obtaining a first equation by Laplace transform of the S-domain equation;

[0100] In the steady state of the multi-level inverter system, the initial state quantity of the first equation is determined to be 0;

[0101] The target current of the branch current and the filter inductor is determined according to the first equation constructed after the steady state.

[0102] Specifically, in order to facilitate calculation, the differential equation of the target state equation is converted into an S-domain equation, and after Laplace transform, a first equation is obtained. Taking two bridge arms as an example, the formula is as follows:

[0103] (6);

[0104] (7);

[0105] (8);

[0106] (9);

[0107] (10);

[0108] wherein, and are the Laplace transforms of and , respectively, and is the initial current value, is the Laplace transform of, is the initial current value.

[0109] In the steady state of the multi-level inverter system, the initial current change has no effect, so the initial state quantity is ignored, that is, 0, and the first equation after the steady state can be solved to determine the branch equation and the target current of the filter inductance. The formula is as follows:

[0110] (11);

[0111] (12);

[0112] (13);

[0113] wherein, and is the branch circuit, is the target current.

[0114] The simplification process of the time domain equation (differential equation) provided in the embodiment can analyze the dynamic characteristics of the system in the S domain, the Laplace transform is convenient for processing the transient response of the system, and the response of the system can be directly solved by the algebraic method without complex differential equation solving skills. Not only simplifies the calculation process, but also provides intuitive system characteristic analysis, which is convenient for system design and optimization, and also provides a powerful tool for fault diagnosis and prediction.

[0115] The step S13 of determining the ripple current change of the filter inductance according to the branch current and the target current needs to obtain the time domain expressions of the corresponding devices, branch currents and target currents at t1 and t2 to ensure the corresponding changes at the two times. Here, it can be realized by Laplace inverse transform, and in some embodiments, the determination of the ripple current change of the filter inductance according to the branch current and the target current comprises:

[0116] According to the first equation corresponding to the branch current and the target current, the second equation corresponding to the current change of the branch current and the target current is determined by Laplace inverse transform;

[0117] When the mutual inductance coefficient and the self-inductance coefficient of the coupled inductance are the same, the equation corresponding to the current change of the target current in the second equation is simplified to obtain the ripple current change of the filter inductance.

[0118] Specifically, taking the two-bridge-arm parallel scheme as an example, the first equation corresponds to the first equation after the above steady state, and the second equation is realized by inverse Laplace transform. It should be noted that the first equation and the second equation here are collectively referred to, not for a specific equation setting. The second equation formula is as follows:

[0119] (14);

[0120] (15);

[0121] (16);

[0122] wherein, , , , respectively represent the branch current of bridge arm A, the branch current of bridge arm B and the target current corresponding to the change of the filter inductance.

[0123] When the mutual inductance and the self-inductance are the same, some parameters will cancel out, making the formula more concise, facilitating analysis and calculation, such as formula:

[0124] (17).

[0125] It should be noted that the ripple current change of the filter inductance corresponding to more than two bridge arms in parallel is:

[0126] (18);

[0127] wherein, is the number of bridge arms, .

[0128] In the case of the largest ripple current change, the required minimum inductance of the filter inductance can be calculated, and the inductance formula corresponding to formula (18) is as follows:

[0129] (19).

[0130] The embodiment of the present application provides a kind of inductance determination method of filter inductor, it is applied to multi-level inverter system, the output end of the bridge arm of multi-level inverter system is connected coupling inductor, coupling inductor connects filter inductor;The modulation wave of at least two bridge arms is 180 ° out of phase, in the structure of this inverter system and the modulation wave of bridge arm 180 ° out of phase carrier interleaving technique, realize the inductance reduction of filter inductor, reduce the space occupied and reduce system cost.Furthermore, the inductance determination mode of filter inductor in this structure, by establishing target state equation, to facilitate subsequent knowing the dynamic change of the output voltage of different bridge arms of the inverter system and the current of filter inductor.According to target state equation, the branch current of the coupling inductor winding of each bridge arm and the corresponding target current of filter are determined, so that it is abstracted into mathematical expression during circuit operation, to determine the branch current and target current by mathematical method.Determine the ripple current variation of filter inductor by taking the determined branch current and target current as subsequent constraint parameter.Furthermore, the inductance of filter inductor is determined based on the ripple current variation of filter inductor, as an important basis for selecting filter inductor, to ensure that the specific inductance is determined on the basis of reducing the inductance of filter inductor, improve the accuracy of selection.

[0131] In some embodiments, as shown in Figure 2 Three-level INPC under corresponding modulation mode, its bridge arm output P, O, N three states, since using carrier interleaving modulation mode, the output state of AB bridge arm is inconsistent at the same time, then it will lead to circulating current, taking positive half cycle as an example, Figure 9 The structure diagram of the single-phase multi-level inverter system of the embodiment of the present application is provided, as shown in Figure 9 The output state of bridge arm A is P, and the output state of bridge arm B is O, forming a circulating current path as indicated by the arrow. In order to suppress the size of the circulating current and reduce the switching tube conduction loss caused by the circulating current, a coupling inductor is connected to the output end of the two bridge arms, the self-inductance of the coupling inductor is , and the mutual inductance is Since the same name end is not on the same side, the inductance of the circulating current is enhanced, that is, the inductance of the circulating current is increased to suppress the size of the circulating current.

[0132] After determining the second equation, the method further comprises:

[0133] According to the equation of each branch current in the second equation, the corresponding circulating current equation in each bridge arm is determined.

[0134] When the mutual inductance coefficient and the self-inductance coefficient of the coupling inductor are the same, the circulating current equation is simplified to obtain a third equation.

[0135] The self-inductance value of the coupling inductor is determined based on the third equation.

[0136] Specifically, the equations of each branch current in the second equation (formula (14) to formula (16)) determine the corresponding circulating current equations in each bridge arm.

[0137] Taking the structure of two bridge arms in parallel as an example, the circulating current formula of the two bridge arms is:

[0138] (20);

[0139] Wherein, when the mutual inductance and the self-inductance are equal, formula (20) can be further simplified as the following formula:

[0140] (21);

[0141] When , there is the maximum circulating current maximum, wherein, is the switching period of the high-frequency switch tube, and the formula is as follows:

[0142] (22);

[0143] It can be seen that, in the t1-t2 time, the bridge arm freewheeling of the bridge arm B, but the current change is negative, the first switch tube and the third switch tube of the bridge arm A, the fifth switch tube and the seventh switch tube of the bridge arm B are turned on at the same time to form circulating current, after defining the maximum circulating current, the self-inductance and mutual inductance of the required coupling inductance can be calculated.

[0144] The self-inductance of the coupling inductance can be obtained from formula (22) as follows:

[0145] (23);

[0146] It can be seen that, when it is extended to bridge arms, the circulating current formula is:

[0147] (24);

[0148] Wherein, .

[0149] The self-inductance of the coupling inductance can be obtained from formula (24) as follows:

[0150] (25);

[0151] The embodiment provided determines the self-inductance of the coupling inductance, suppresses the circulating current size caused by the output state of the interleaved parallel inverter bridge arm, reduces the switching tube conduction loss caused by the circulating current, and improves the inverter efficiency.

[0152] In some embodiments, determining the inductance of the filter inductance based on the ripple current change of the filter inductance comprises:

[0153] obtaining a first relationship between an output voltage duty cycle of the multi-level inverter system and a grid voltage;

[0154] obtaining a second relationship of the first relationship corresponding to a time variation at a current peak value;

[0155] determining an inductance of the filter inductor according to the first relationship, the second relationship, and a ripple current variation of the filter inductor.

[0156] Specifically, the filter inductor At a power frequency sinusoidal peak current, a certain inductance needs to be met to achieve a ripple current . is a peak value of an output current sinusoid. Since the topology is an inverter INPC, and SPWM modulation is adopted, the first relationship of the output voltage duty cycle is ; therefore, at the current peak value, the second relationship is , , is a peak value of an output voltage sinusoid. is a switching period of a high-frequency switch tube, and the corresponding inductance formula is:

[0157] (19).

[0158] The determination process provided by the embodiment based on the ripple current variation of the filter inductor to determine the inductance of the filter inductor can effectively filter out the high-frequency ripple current, improve the output quality of the circuit, reduce the inductance of the filter inductor of the inverter output, and reduce the system cost.

[0159] In some embodiments, after the inductance of the filter inductor is determined, the method further comprises:

[0160] obtaining a first inductance of the filter inductor determined by a preset manner of the multi-level inverter system;

[0161] determining a first ratio according to the inductance of the filter inductor and the first inductance;

[0162] if the first ratio is less than 1, selecting a corresponding filter inductor device according to the inductance of the filter inductor.

[0163] Specifically, the first inductance of the filter inductor determined by the preset manner is , and the formula is as follows:

[0164] (26).

[0165] Let the ripple currents be the same, i.e. .

[0166] The first ratio is obtained by setting the ratio of the inductance of the filter inductor to the first inductance, that is, the formula is as follows:

[0167] (27).

[0168] The interleaved parallel inductance is smaller than the traditional three-level inverter inductance. , For example, the first ratio is 0.356, and the filter inductance of the interleaved parallel inverter topology is 0.356 times the required inductance of the traditional three-level inverter inductance.

[0169] The multi-level inverter system provided by the embodiment is compared with the inductance corresponding to the traditional three-level inverter to determine that the inductance determined by the embodiment is smaller, thereby saving the system cost.

[0170] Figure 10 A simulation schematic diagram of the coupled inductor interleaved parallel three-level staggered paving provided by the embodiment of the application is shown in Figure 10 , from which it can be seen that the simulation current macroscopic waveform and the driving waveform can be seen. Figure 11 A detail expansion diagram based on Figure 10 provided by the embodiment of the application is shown in Figure 11 , from which it can be seen that the influence on the current in the actual application process at t1 to t2 can be intuitively reflected. Figure 12 A simulation schematic diagram of the coupled inductor maximum ripple current provided by the embodiment of the application is shown in Figure 12 , which is based on a special case in Figure 11 , at 75% duty ratio, the maximum ripple current value of the coupled inductor. In Figure 10 , 11 , 12, the upper sub-diagram of the simulation schematic diagram, mark 1 is the current waveform of the coupled inductor branch corresponding to the bridge arm A, and mark 2 is the current waveform of the coupled inductor branch corresponding to the bridge arm B. The lower sub-diagram of the simulation schematic diagram is the driving waveform of the first switch tube in the bridge arm A and the fifth switch tube in the bridge arm B corresponding to the interleaved parallel circuit switch tube.

[0171] The above detailed description of the inductance determination method of the filter inductor corresponds to each embodiment, and on this basis, the application also discloses a filter inductor inductance determination device corresponding to the above method, which is applied to a multi-level inverter system, the multi-level inverter system comprising a coupled inductor, a filter inductor and at least two bridge arms in parallel relationship; the output ends of the at least two bridge arms are connected to the coupled inductor, and the coupled inductor is connected to the filter inductor; the modulation waves of the at least two bridge arms are 180° out of phase, Figure 13 A structure diagram of the filter inductor inductance determination device provided by the embodiment of the application is shown in Figure 13 , the filter inductor inductance determination device comprises:

[0172] The establishing module 11 is configured to establish a target state equation between the coupled inductor, the filter inductor and the grid voltage corresponding to each bridge arm;

[0173] The first determining module 12 is configured to determine a branch current of the coupled inductor output winding and a target current of the filter inductor of each bridge arm according to the target state equation;

[0174] The second determining module 13 is configured to determine a ripple current variation of the filter inductor according to the branch current and the target current;

[0175] The third determining module 14 is configured to determine an inductance of the filter inductor based on the ripple current variation of the filter inductor.

[0176] Since the embodiments of the device part correspond to the above-mentioned embodiments, the embodiments of the device part are described with reference to the embodiments of the above-mentioned method part, and will not be described here.

[0177] For the filter inductor inductance determination device provided by the present application, please refer to the above-mentioned method embodiments, and the present application will not be described here, which has the same beneficial effects as the above-mentioned filter inductor inductance determination method.

[0178] Figure 14 A structural diagram of an electronic device provided by an embodiment of the present application is shown in FIG. 1, which includes: Figure 14

[0179] The memory 21 is configured to store a computer program;

[0180] The processor 22 is configured to execute the computer program to realize the steps of the filter inductor inductance determination method.

[0181] The electronic device provided by the present embodiment can include but is not limited to a smart phone, a tablet computer, a notebook computer or a desktop computer, etc.

[0182] ​The processor 22 can include one or more processing cores, such as a 4-core processor, an 8-core processor, etc. The processor 22 can be implemented in at least one of a hardware form of a digital signal processor (DSP), a field-programmable gate array (FPGA), a programmable logic array (PLA), etc. The processor 22 can also include a main processor and a coprocessor. The main processor is a processor for processing data in a wake-up state, also referred to as a central processing unit (CPU). The coprocessor is a low-power processor for processing data in a standby state. In some embodiments, the processor 22 can be integrated with a graphics processing unit (GPU) for rendering and drawing content required to be displayed by the display screen. In some embodiments, the processor 22 can further include an artificial intelligence (AI) processor for processing computing operations related to machine learning.

[0183] The memory 21 can include one or more computer-readable storage media that can be non-transitory. The memory 21 can further include a high-speed random access memory, and a nonvolatile memory such as one or more disk storage devices, flash storage devices. In this embodiment, the memory 21 is at least used to store a computer program 211, wherein the computer program is loaded and executed by the processor 22, and can implement the related steps of the filter inductance determination method disclosed in any of the preceding embodiments. In addition, the resources stored by the memory 21 can further include an operating system 212 and data 213, etc., and the storage manner can be temporary storage or permanent storage. The operating system 212 can include Windows, Unix, Linux, etc. The data 213 can include but is not limited to data related to the filter inductance determination method, etc.

[0184] In some embodiments, the electronic device can further include a display screen 23, an input / output interface 24, a communication interface 25, a power supply 26, and a communication bus 27.

[0185] Those skilled in the art can understand that the structure shown in the above embodiments does not constitute a limitation on the electronic device, and can include more or fewer components than those shown. Figure 14 The structure shown in the above embodiments does not constitute a limitation on the electronic device, and can include more or fewer components than those shown.

[0186] The processor 22 calls instructions stored in the memory 21 to implement the filter inductance inductance determination method provided by any of the above embodiments.

[0187] For the electronic device provided by the present application, refer to the above method embodiments, and the present application will not be described here again, which has the same beneficial effects as the filter inductance inductance determination method described above.

[0188] Further, the present application also provides a computer readable storage medium, and the computer readable storage medium stores a computer program, and the computer program is executed by the processor 22 to implement the steps of the filter inductance inductance determination method.

[0189] It can be understood that if the method in the above embodiments is implemented in the form of a software function unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and executes all or part of the steps of the method of each embodiment of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (Read-Only Memory, ROM), a random access memory (Random Access Memory, RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0190] For the computer readable storage medium provided by the present application, refer to the above method embodiments, and the present application will not be described here again, which has the same beneficial effects as the filter inductance inductance determination method described above.

[0191] The filter inductance inductance determination method, device, equipment and medium provided by the present application are described in detail above. The embodiments in the specification are described in a progressive manner, and each embodiment mainly describes the differences from other embodiments. The same or similar parts of each embodiment can be referred to. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be referred to the method part. It should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, the present application can be improved and modified, and these improvements and modifications also fall within the protection scope of the present application.

[0192] It also needs to be explained that in the present specification, the relational terms such as first and second and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

Claims

1. A method for determining the inductance of a filter inductor, characterized in that, This invention is applied to a multilevel inverter system, which includes a coupling inductor, a filter inductor, and at least two bridge arms connected in parallel; the output terminals of the at least two bridge arms are connected to the coupling inductor, and the coupling inductor is connected to the filter inductor. The method includes at least two of the bridge arms having their modulated waves out of phase by 180°. Establish the target state equations between the coupling inductance of each bridge arm, the filter inductance, and the grid voltage; The branch current of the output winding of the coupled inductor of each bridge arm and the target current of the filter inductor are determined according to the target state equation. The ripple current variation of the filter inductor is determined based on the branch current and the target current. The inductance of the filter inductor is determined based on the change in ripple current of the filter inductor.

2. The method for determining the inductance of a filter inductor according to claim 1, characterized in that, The establishment of the target state equations between the coupling inductors of each bridge arm, the filter inductors, and the grid voltage includes: Establish the first voltage formula for each bridge arm corresponding to the coupled inductor, relating the self-inductance coefficient, mutual inductance coefficient, and rate of change of current in each bridge arm. Establish a second voltage formula for the filter inductor between the unknown inductance parameter of the filter inductor and the sum of the current values ​​of each bridge arm; Establish the relationship formula between each bridge arm, the unknown inductance parameters of the filter inductor, and the grid voltage; The first voltage formula, the second voltage formula, and the relational formula are used as the target state equation.

3. The method for determining the inductance of a filter inductor according to claim 2, characterized in that, The branch current of the output winding of the coupled inductor and the target current of the filter inductor of each bridge arm are determined according to the target state equation, including: The target state equation is converted into an S-domain equation; The first equation is obtained by performing a Laplace transform on the S-domain equation. Under the steady-state condition of the multi-level inverter system, the initial state variables of the first equation are determined to be 0; The branch current and the target current of the filter inductor are determined based on the first equation constructed after steady state.

4. The method for determining the inductance of a filter inductor according to claim 3, characterized in that, Determining the ripple current change of the filter inductor based on the branch current and the target current includes: The second equation corresponding to the change in current of the branch current and the target current is determined by performing an inverse Laplace transform based on the first equation corresponding to ... second equation corresponding to the change in current of the branch current and the target current. When the mutual inductance coefficient of the coupled inductor is the same as the self-inductance coefficient, the equation corresponding to the current change of the target current in the second equation is simplified to obtain the ripple current change of the filter inductor.

5. The method for determining the inductance of a filter inductor according to claim 4, characterized in that, After determining the second equation, the method further includes: Determine the corresponding circulating current equation in each bridge arm based on the equation of each branch current in the second equation. When the mutual inductance coefficient of the coupled inductor is the same as the self-inductance coefficient, the circulating current equation is simplified to obtain a third equation; The self-inductance value of the coupled inductor is determined based on the aforementioned third-party process.

6. The method for determining the inductance of a filter inductor according to claim 4, characterized in that, Determining the inductance of the filter inductor based on the change in ripple current of the filter inductor includes: Obtain the first relationship between the output voltage duty cycle of the multilevel inverter system and the grid voltage; Obtain the first relationship corresponding to the current peak value and the second relationship of time variation; The inductance of the filter inductor is determined based on the first relationship, the second relationship, and the change in the ripple current of the filter inductor.

7. The method for determining the inductance of a filter inductor according to claim 1, characterized in that, After determining the inductance of the filter inductor, the method further includes: Obtain the first inductance of the filter inductor determined by a preset method in the multi-level inverter system; A first ratio is determined based on the inductance of the filter inductor and the first inductance; If the first ratio is less than 1, then the corresponding filter inductor device is selected according to the inductance of the filter inductor.

8. A device for determining the inductance of a filter inductor, characterized in that, This invention is applied to a multilevel inverter system, which includes a coupling inductor, a filter inductor, and at least two bridge arms connected in parallel; the output terminals of the at least two bridge arms are connected to the coupling inductor, and the coupling inductor is connected to the filter inductor. The modulation waves of at least two of the bridge arms are out of phase by 180°, and the device includes: A module is established to establish the target state equation between the coupling inductor, the filter inductor, and the grid voltage for each bridge arm. The first determining module is used to determine the branch current of the output winding of the coupled inductor of each bridge arm and the target current of the filter inductor according to the target state equation. The second determining module is used to determine the ripple current change of the filter inductor based on the branch current and the target current. The third determining module is used to determine the inductance of the filter inductor based on the change in the ripple current of the filter inductor.

9. An electronic device, characterized in that, Includes memory used to store computer programs; A processor, configured to execute the computer program to implement the steps of the method for determining the inductance of a filter inductor as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the method for determining the inductance of a filter inductor as described in any one of claims 1 to 7.

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