Two-level converter frequency domain characteristic analysis method, device, equipment and medium

Abstract

The invention belongs to the field of steady-state and small-signal frequency domain characteristic analysis of two-level current converters, and particularly relates to a frequency domain characteristic analysis method, device and equipment of a two-level current converter and a medium. The method comprises the following steps: respectively constructing a steady-state working point frequency domain model and a small signal component frequency domain model of a main circuit by superposing an alternating-current voltage oscillation component and a small signal component on an alternating-current side, and deriving frequency distribution of a steady-state component transmission path based on a coupling relationship between the oscillation component and an alternating-current fundamental-frequency component, establishing a frequency domain model containing steady-state vectors such as alternating current, direct current voltage, modulation signals and the like; a small signal matrix of AC voltage, current and modulation signals is constructed through a small signal component frequency conversion relation, and frequency distribution characteristics of a small signal transmission path are analyzed. A multi-harmonic interactive coupling mechanism in an oscillation scene is accurately described, and the problem that a traditional model is difficult to describe steady-state offset and multi-frequency interaction is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of two-level converter steady-state and small-signal frequency domain characteristic analysis, and particularly relates to a two-level converter frequency domain characteristic analysis method, device, equipment and medium. BACKGROUND

[0002] With the large-scale promotion of global new energy bases to desert areas, the topology of power systems has changed significantly: the support ability of synchronous power sources in local areas is weakened or even lost, and multi-stage voltage-boosting AC collection systems form extremely weak power grids (short-circuit ratio SCR is in the interval 1.0-1.5), and the problem of wideband oscillation caused by new energy grid connection is becoming increasingly serious. In the extremely weak power grid environment, the oscillation voltage amplitude generated by the coupling of the oscillation current through the grid impedance is significantly higher than the current itself, and the wideband oscillation phenomenon characterized by voltage fluctuation becomes the main threat to the stable operation of the system.

[0003] As the core equipment of new energy grid connection, the mathematical model of the two-level converter contains strong nonlinear links such as IGBT switching, PWM modulation, Park transformation and PLL phase locking, and the DC bus presents a non-ideal voltage source characteristic, and its dynamic process will have a complex influence on the multi-frequency interaction characteristics and stability criterion accuracy in wideband oscillation. When the system enters the oscillation scene, the running state of the converter is disturbed by the superimposed oscillation component, the steady-state operating point and the frequency domain response characteristics change in nature, which leads to serious challenges for traditional frequency domain analysis methods. SUMMARY

[0004] The purpose of the present application is to provide a two-level converter frequency domain characteristic analysis method, device, equipment and medium to at least solve or improve one of the problems mentioned in the background.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: In a first aspect, the present application provides a two-level converter frequency domain characteristic analysis method, the two-level converter frequency domain characteristics including a steady-state operating point frequency domain model of the main circuit and a small-signal component frequency domain model; the method comprising: superimposing an AC voltage oscillation component on the AC side of the two-level converter to obtain an AC voltage steady-state component; obtaining a transfer steady-state component according to the coupling relationship between the AC voltage oscillation component and the AC current fundamental frequency component; determining the frequency of the AC voltage steady-state component and the transfer steady-state component, and determining the steady-state component transfer path frequency distribution according to the frequency of the AC voltage steady-state component and the transfer steady-state component; based on the AC voltage steady-state component, the transfer steady-state component and the steady-state component transfer path frequency distribution, a steady-state vector is constructed; based on the steady-state vector, a steady-state operating point frequency domain model is constructed; wherein the transfer steady-state component includes a DC voltage steady-state component, an AC modulation signal steady-state component and an AC current steady-state component; Superimpose AC voltage small signal component to AC side of two-level converter, get DC voltage small signal component, determine AC modulation voltage small signal component according to DC voltage small signal component and AC modulation signal steady component, determine AC current small signal component according to AC modulation voltage small signal component and AC voltage small signal component; determine the frequency of DC voltage small signal component, AC voltage small signal component, AC modulation voltage small signal component and AC current small signal component respectively, determine small signal component transmission path frequency distribution according to the frequency of DC voltage small signal component, AC voltage small signal component, AC modulation voltage small signal component and AC current small signal component; according to AC voltage small signal component, AC modulation voltage small signal component, AC current small signal component and transmission path frequency distribution, respectively construct DC voltage small signal component, AC voltage small signal matrix, AC current small signal matrix and AC modulation signal small signal matrix, construct main circuit small signal component frequency domain model according to DC voltage small signal component, AC voltage small signal matrix, AC current small signal matrix and AC modulation signal small signal matrix.

[0006] Further, the steady-state operating point frequency domain model comprises: Determine the relationship between the three-phase modulation voltage steady-state vector of the two-level converter , the DC voltage steady-state vector , the three-phase AC modulation signal steady-state vector :

[0007] Two-level converter AC circuit frequency domain steady-state model:

[0008]

[0009] In the formula, is the AC voltage steady-state vector; is the modulation voltage steady-state vector; is the AC filter inductance impedance under steady-state frequency sequence; is the AC current steady-state vector; L f is the AC filter inductance; j is the imaginary unit; is the fundamental frequency; is the oscillation frequency; , , wherein g is the highest iteration number considered; DC bus frequency domain steady-state model:

[0010]

[0011]

[0012] Where, is the DC voltage steady-state matrix; is the DC current steady-state vector; is the DC capacitance steady-state vector; l is the phase sequence, a, b, c represent the three phases respectively; is the steady-state component of DC current; is the DC bus capacitor.

[0013] Furthermore, the steady-state vector includes an AC current steady-state vector, a DC voltage steady-state vector, an AC modulated signal steady-state vector, and an AC voltage steady-state vector.

[0014] Furthermore, the AC voltage small signal matrix is ​​expressed as:

[0015] Where, The frequency is The small signal component of the AC voltage; The AC current small signal matrix is ​​expressed as:

[0016] Where, The frequency is The small signal component of the AC current; The small signal matrix of the AC modulated signal is expressed as:

[0017] Where, The frequency is The small signal component of the AC modulated signal.

[0018] Furthermore, the frequency domain model of the small signal component of the main circuit includes: Frequency domain small signal model of two-level converter modulation voltage:

[0019] AC circuit frequency domain small signal model:

[0020]

[0021] DC bus frequency domain small signal model:

[0022]

[0023] Where, is a voltage small signal vector; K m is a PWM gain; is a three-phase AC modulation signal steady-state vector; is a DC voltage small signal matrix; is an AC modulation signal small signal matrix; is an AC voltage small signal vector; is an AC filter inductance impedance under a small signal frequency sequence; is an AC current small signal matrix; is a DC bus capacitance admittance under a small signal frequency sequence.

[0024] In a second aspect, the present application provides a two-level converter frequency domain characteristic analysis device, the two-level converter frequency domain characteristics including a steady-state operating point frequency domain model of a main circuit and a small signal component frequency domain model; the device includes: a first analysis module, configured to superimpose an AC voltage oscillation component to an AC side of the two-level converter to obtain an AC voltage steady-state component; obtain a transfer steady-state component according to a coupling relationship between the AC voltage oscillation component and an AC current fundamental component; determine frequencies of the AC voltage steady-state component and the transfer steady-state component, and determine a steady-state component transfer path frequency distribution according to the frequencies of the AC voltage steady-state component and the transfer steady-state component; construct a steady-state vector based on the AC voltage steady-state component, the transfer steady-state component and the steady-state component transfer path frequency distribution; construct a steady-state operating point frequency domain model based on the steady-state vector; wherein the transfer steady-state component includes a DC voltage steady-state component, an AC modulation signal steady-state component and an AC current steady-state component; a second analysis module, configured to superimpose an AC voltage small signal component to the AC side of the two-level converter to obtain a DC voltage small signal component, determine an AC modulation voltage small signal component according to the DC voltage small signal component and the AC modulation signal steady-state component, and determine an AC current small signal component according to the AC modulation voltage small signal component and the AC voltage small signal component; determine frequencies of the DC voltage small signal component, the AC voltage small signal component, the AC modulation voltage small signal component and the AC current small signal component respectively, and determine a small signal component transfer path frequency distribution according to the frequencies of the DC voltage small signal component, the AC voltage small signal component, the AC modulation voltage small signal component and the AC current small signal component; construct a DC voltage small signal matrix, an AC voltage small signal matrix, an AC current small signal matrix and an AC modulation signal small signal matrix respectively according to the AC voltage small signal component, the AC modulation voltage small signal component, the AC current small signal component and the transfer path frequency distribution, and construct a main circuit small signal component frequency domain model according to the DC voltage small signal matrix, the AC voltage small signal matrix, the AC current small signal matrix and the AC modulation signal small signal matrix.

[0025] Further, the steady-state operating point frequency domain model includes: Determine the steady-state vector of three-phase modulation voltage of two-level converter , DC voltage steady-state vector , steady-state vector of three-phase AC modulation signal The relationship between them is:

[0026] Frequency domain steady-state model of the two-level converter AC circuit:

[0027]

[0028] Where, is the steady-state AC voltage vector; is the steady-state vector of the modulation voltage; is the AC filter inductor impedance under steady-state frequency sequence; is the steady-state vector of AC current; L f is the AC filter inductor; j is the imaginary unit; is the fundamental frequency; is the oscillation frequency; , ,in g is the highest number of iterations considered; DC bus frequency domain steady-state model:

[0029]

[0030]

[0031] Where, is the DC voltage steady-state matrix; is the DC current steady-state vector; is the DC capacitance steady-state vector; l is the phase sequence, a, b, c represent the three phases respectively; is the steady-state component of DC current; is the DC bus capacitor.

[0032] Furthermore, the frequency domain model of the small signal component of the main circuit includes: Frequency domain small signal model of two-level converter modulation voltage:

[0033] AC circuit frequency domain small signal model:

[0034]

[0035] Direct current bus frequency domain small signal model:

[0036]

[0037] In the formula, The modulation voltage small signal vector is K m The PWM gain is K The three-phase alternating current modulation signal steady-state vector is K The direct current voltage small signal matrix is K The alternating current modulation signal small signal matrix is K The alternating current voltage small signal vector is K The alternating current filter inductance impedance under the small signal frequency sequence is K The alternating current current small signal matrix is K The direct current bus capacitance admittance under the small signal frequency sequence is K

[0038] In a third aspect, the application provides an electronic device, comprising a processor and a memory, wherein the processor is configured to execute a computer program stored in the memory to implement the two-level converter frequency domain characteristic analysis method as described above.

[0039] In a fourth aspect, the application provides a computer readable storage medium, wherein the computer readable storage medium stores at least one instruction, and the at least one instruction is executed by a processor to implement the two-level converter frequency domain characteristic analysis method as described above.

[0040] The application aims at the problem of frequency domain characteristic analysis of two-level converters caused by superimposed oscillation components in extremely weak power grid environment, and realizes accurate description of the dynamic characteristics of the converter by constructing a steady-state and small signal frequency domain model, and the technical effects are as follows: The traditional frequency domain analysis method cannot consider the interference of the oscillation component on the steady-state working point of the converter, resulting in insufficient model accuracy. The application superimposes an oscillation component on the alternating current side, deduces the frequency distribution of the steady-state component transmission path based on the coupling relationship, constructs a frequency domain model including alternating current, direct current voltage, modulation signal and other steady-state vectors, accurately describes the offset characteristics of the steady-state working point of the converter in the oscillation scenario, solves the interference problem of the non-linear link and the non-ideal direct current bus on the steady-state model, and provides an accurate model basis for the steady-state characteristic analysis of the converter in the wide frequency oscillation scenario.

[0041] Aiming at the multi-frequency interaction problem of oscillation component and fundamental component in wide frequency oscillation, the present application deduces the frequency distribution of each component transmission path through superimposing small signal component and combining frequency conversion relationship, constructs the small signal matrix model of alternating voltage, current and modulation signal, and accurately analyzes the coupling law of oscillation frequency and fundamental frequency in Park transformation, PLL phase locking and other links. The method effectively solves the problem that the traditional model cannot characterize the multi-frequency interaction caused by the coupling of oscillation voltage through grid impedance, and realizes the fine description of the small signal frequency domain response characteristics of the converter.

[0042] By analyzing the transmission path frequency distribution of steady state and small signal component through iterative modulation, the present application breaks through the technical bottleneck that multi-harmonic components are difficult to clarify under extremely weak grid, and can quantitatively describe the influence path of oscillation component on the frequency domain characteristics of the converter. The present application lays a theoretical foundation for establishing a converter impedance analysis model considering the oscillation scenario, and can be directly applied to the stability criterion optimization under the wide frequency oscillation scenario, and provides key technical support for the wide frequency oscillation suppression control strategy design of the new energy grid-connected system.

[0043] The frequency domain characteristic analysis method provided by the present application fully considers the characteristics that the oscillation voltage amplitude is higher than the current under extremely weak grid, and accurately models the frequency domain response of the converter under the oscillation scenario, which can effectively guide the optimization of converter control parameters, reduce the system instability risk caused by wide frequency oscillation, and significantly improve the dynamic stability and engineering practicability of the new energy grid-connected system. BRIEF DESCRIPTION OF DRAWINGS

[0044] The drawings accompanying the specification of the present application are used to provide further understanding of the present application, the illustrative embodiments of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application. In the drawings: Figure 1 A flow chart of a two-level converter frequency domain characteristic analysis method according to an embodiment of the present application; Figure 2 A schematic diagram of a two-level converter topology according to an embodiment of the present application; Figure 3 A schematic diagram of steady state component transmission path and frequency distribution of a two-level converter according to an embodiment of the present application; Figure 4 A schematic diagram of small signal transmission path and frequency distribution of a two-level converter according to an embodiment of the present application; Figure 5 A schematic diagram of alternating voltage steady state waveform and FFT result according to an embodiment of the present application; Figure 6 A schematic diagram of direct current voltage steady state waveform and FFT result according to an embodiment of the present application; Figure 7 A schematic diagram of alternating voltage small signal waveform and FFT result according to an embodiment of the present application; Figure 8 A schematic diagram of a DC voltage small signal waveform and FFT results in an embodiment of the present invention; Figure 9 This is a structural block diagram of a two-level converter frequency domain characteristic analysis device according to an embodiment of the present invention; Figure 10 This is a structural block diagram of an electronic device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0046] The following detailed description is an exemplary description, which is intended to provide further detailed description of the present invention. Unless otherwise indicated, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0047] Example 1 To address the challenges of analyzing VSC frequency-domain characteristics in scenarios with superimposed oscillating components, this paper proposes a method for analyzing VSC frequency-domain characteristics in these scenarios by using frequency conversion relationships to determine the VSC steady-state operating point and small-signal frequency components. This method accurately characterizes the multiharmonic interaction coupling between the oscillating component and the fundamental frequency component, and details the impact of the oscillating component on the VSC frequency-domain characteristics. This method accurately analyzes the frequency-domain characteristics of VSCs in these scenarios, providing key technical support for the impedance modeling, analysis, and control of two-level converters in these scenarios.

[0048] It should be noted that the two-level converter topology includes a DC bus capacitor 1, an IGBT inverter module 2, and a smoothing reactor 3. The DC bus capacitor 1's two ends are connected to the DC side of the IGBT inverter module 2, which consists of a set of six-pulse IGBT inverter valves. The IGBT inverter module outputs three-phase current, which is sent out through the smoothing reactor 3. Figure 2 middle, 、 、 are the AC voltages of phases a, b, and c respectively, 、 、 are the AC currents of phases a, b, and c respectively. 、 、 They are the AC modulation voltages of phases a, b, and c respectively, such as Figure 2 shown.

[0049] like Figure 1 As shown, a method for analyzing the frequency domain characteristics of a two-level converter is provided. The frequency domain characteristics of the two-level converter include a steady-state operating point frequency domain model of the main circuit and a small signal component frequency domain model. The method includes: S1. Superimpose an AC voltage oscillation component on the AC side of the two-level converter to obtain an AC voltage steady-state component; obtain a transfer steady-state component based on the coupling relationship between the AC voltage oscillation component and the AC current fundamental frequency component; determine the frequencies of the AC voltage steady-state component and the transfer steady-state component, and determine the frequency distribution of the steady-state component transfer path based on the frequencies of the AC voltage steady-state component and the transfer steady-state component; construct a steady-state vector based on the AC voltage steady-state component, the transfer steady-state component, and the frequency distribution of the steady-state component transfer path; construct a steady-state operating point frequency domain model based on the steady-state vector; wherein, the transfer steady-state component includes a DC voltage steady-state component, an AC modulation signal steady-state component, and an AC current steady-state component.

[0050] In one embodiment, the steady-state vector includes an AC current steady-state vector, a DC voltage steady-state vector, an AC modulation signal steady-state vector, and an AC voltage steady-state vector.

[0051] In one embodiment, step S1 specifically includes: Step S10: superimpose the oscillation component and analyze the frequency distribution of the first iteration of the steady-state component transmission path.

[0052] Step S101: is the fundamental frequency, is the oscillation frequency; according to the instantaneous power balance, the frequency of the a-phase AC voltage is The oscillation component The frequency of the AC current in phase a is The fundamental frequency component Multiplying by, will result in AC power generation frequency of According to the instantaneous power balance relationship, the DC power will generate a frequency of The steady-state component further causes the DC voltage to generate a frequency of The steady-state component ; Step S102: According to the frequency domain relationship between the modulation voltage and the DC voltage, the DC voltage has a frequency of The steady-state component The frequency of the a-phase AC modulation signal is The fundamental frequency component Multiplying them together results in a phase modulation voltage with a frequency of The steady-state component , DC voltage steady-state component The frequency of the a-phase AC modulation signal is The fundamental frequency component Multiplying, the a-phase modulation voltage generates a steady-state component with a frequency of ; ; In step S103, the steady-state component with a frequency of in the a-phase modulation voltage acts on the filter inductance with the oscillation component with a frequency of in the a-phase alternating voltage , resulting in the a-phase alternating current generating a steady-state component with a frequency of ; , the steady-state component with a frequency of in the a-phase alternating modulation voltage acts on the filter inductance, resulting in the a-phase alternating current generating a steady-state component with a frequency of ; ; In step S104, the superimposed alternating voltage oscillation component with a frequency of after Park transformation to the dq rotating coordinate system, the alternating voltage d, q-axis components and the phase-locked angle all generate steady-state components with a frequency of ; , and . At the same time, the alternating current d, q-axis components also generate steady-state components with a frequency of ; , , under the action of alternating current control, the alternating modulation signal d, q-axis components generate steady-state components with a frequency of ; , , after Park inverse transformation, resulting in the a-phase alternating modulation signal generating a steady-state component with a frequency of ; and a steady-state component with a frequency of ; ; In step S11, based on the newly generated frequency steady-state components in the first iteration, the frequency distribution of the second iteration of the transmission path is analyzed; In step S111, the oscillation component with a frequency of in the alternating voltage steady-state component multiplies the steady-state component with a frequency of in the a-phase alternating current , which will result in the alternating power generating a steady-state component with a frequency of , therefore, the direct current power will generate a steady-state component with a frequency of , further resulting in the direct current voltage generating a steady-state component with a frequency of ; ; Step S112: The DC voltage has a frequency of The steady-state component The frequency of the a-phase AC modulation signal is The fundamental frequency component Multiplying them together results in a phase modulation voltage with a frequency of The steady-state component , DC voltage steady-state component The frequency of the a-phase AC modulation signal is The steady-state component Multiplying them together results in a phase modulation voltage with a frequency of The steady-state component ; Step S113, the frequency of the a-phase modulation voltage is The steady-state component Acting on the filter inductor, the frequency of the AC current in phase A is The steady-state component , similarly, the frequency of the a-phase AC modulation voltage is The steady-state component Acting on the filter inductor, it will cause the a-phase AC current to generate a frequency of The steady-state component ; Step S114, the frequency is The steady-state component of the AC voltage After Park transformation to the dq rotating coordinate system, the AC voltage d-axis, q-axis components and phase-locked angle will generate a frequency of The steady-state component 、 and At the same time, the d and q axis components of the AC current will also generate frequency The steady-state component 、 , the d and q axis components of the AC modulation signal generate frequencies The steady-state component 、 After Park inverse transformation, the a-phase AC modulation signal will generate a frequency of The steady-state component and the frequency is The steady-state component ; Step S12: Analyze the steady-state component transmission path h The frequency distribution after the first iteration; h After iterations, the DC voltage will generate a frequency of The steady-state component , a-phase modulation voltage, AC current, AC modulation signal will generate a frequency of The steady-state components, phase-locked angle, AC voltage d, q-axis components and AC current d, q-axis components will produce a frequency of The oscillation component 、 、 、 、 The above process is repeated and finally reaches dynamic balance; the steady-state component transmission path and frequency distribution of the two-level converter are as follows: Figure 3 As shown; Step S13: constructing each steady-state frequency domain vector according to the interactive coupling characteristics of the fundamental frequency component and the oscillation component; A frequency of After the AC voltage oscillation component, the two-level converter not only contains the fundamental frequency and oscillation frequency The steady-state component also contains the linear combination frequency of the two ( , ), where g is the highest number of iterations considered, from which each steady-state vector can be constructed; Step S131: Taking phase a as an example, the steady-state AC voltage vector of phase a It can be expressed as (1) In the formula, each steady-state component is expressed in the form of a complex vector, , is the amplitude of the fundamental frequency component of the a-phase AC voltage, is the phase of the fundamental frequency component of the AC voltage of phase a, , The frequency of the AC voltage of phase a is The amplitude of the steady-state component of The fundamental frequency of the a-phase AC voltage is The phase of the steady-state component of the subscript "(1,0)" indicates that the frequency combination is ,Right now Indicates that the frequency of the AC voltage of phase a is The steady-state component of Indicates that the frequency of the AC voltage of phase a is The steady-state component of , the superscript “*” indicates the conjugate operation, Indicates that the frequency of the AC voltage of phase a is The oscillating component of Indicates that the frequency of the AC voltage of phase a is The oscillation component of ; Indicates that the frequency of the AC voltage of phase a is the steady-state component of the a-phase AC voltage with a frequency of the steady-state component of the a-phase AC voltage with a frequency of the steady-state component of the a-phase AC voltage with a frequency of , the steady-state component of the a-phase AC voltage with a frequency of the steady-state component of the a-phase AC voltage with a frequency of the steady-state component of the a-phase AC voltage with a frequency of the steady-state component of the a-phase AC voltage with a frequency of , the steady-state component of the a-phase AC voltage with a frequency of the steady-state component of the a-phase AC voltage with a frequency of the steady-state component of the a-phase AC voltage with a frequency of the steady-state component of the a-phase AC voltage with a frequency of ; the a-phase AC current steady-state vector the a-phase AC modulation signal steady-state vector are respectively expressed as: (2) In the formula, the a-phase AC current steady-state fundamental frequency component, the a-phase AC current oscillation component with a frequency of the a-phase AC current oscillation component with a frequency of the a-phase AC current oscillation component with a frequency of the a-phase AC current oscillation component with a frequency of ; the a-phase AC current steady-state component with a frequency of the a-phase AC current steady-state component with a frequency of the a-phase AC current steady-state component with a frequency of the a-phase AC current steady-state component with a frequency of , the a-phase AC current steady-state component with a frequency of the a-phase AC current steady-state component with a frequency of the a-phase AC current steady-state component with a frequency of the a-phase AC current steady-state component with a frequency of , the a-phase AC current steady-state component with a frequency of the a-phase AC current steady-state component with a frequency of the a-phase AC current steady-state component with a frequency of the a-phase AC current steady-state component with a frequency of ; (3) In the formula, the a-phase AC modulation signal steady-state fundamental frequency component, the a-phase AC modulation signal oscillation component with a frequency of the a-phase AC modulation signal oscillation component with a frequency of , the a-phase AC modulation signal oscillation component with a frequency of The steady-state component of Indicates that the frequency of the a-phase AC modulation signal is The steady-state component of ; Indicates that the frequency of the a-phase AC modulation signal is The steady-state component of Indicates that the frequency of the a-phase AC modulation signal is The steady-state component of , Indicates that the frequency of the a-phase AC modulation signal is The steady-state component of Indicates that the frequency of the a-phase AC modulation signal is The steady-state component of ; Step S133: DC voltage steady-state matrix It can be expressed as (4) Where, is the steady-state value of DC voltage, Indicates that the DC voltage frequency is The steady-state component of Indicates that the DC voltage frequency is The steady-state component of ; Indicates that the DC voltage frequency is The steady-state component of Indicates that the DC voltage frequency is The steady-state component of , Indicates that the DC voltage frequency is The steady-state component of Indicates that the DC voltage frequency is The steady-state component of ; Step S134, and the phase-locked angle The frequency domain steady-state operating points of the relevant sine and cosine functions are: (5) Where, is a sine function The steady-state vector of Represents the sine function Frequency is The steady-state component of Represents the sine function Frequency is The steady-state component of , Represents the sine function Frequency is the steady-state component of denotes a sinusoidal function with a frequency of the steady-state component of , denotes a sinusoidal function with a frequency of the steady-state component of denotes a sinusoidal function with a frequency of the steady-state component of , denotes a sinusoidal function with a frequency of the steady-state component of denotes a sinusoidal function with a frequency of the steady-state component of , denotes a sinusoidal function with a frequency of the steady-state component of denotes a sinusoidal function with a frequency of the steady-state component of ; (6) wherein is the steady-state vector of the cosine function denotes a cosine function with a frequency of the steady-state component of denotes a cosine function with a frequency of the steady-state component of , denotes a cosine function with a frequency of the steady-state component of denotes a cosine function with a frequency of the steady-state component of , denotes a cosine function with a frequency of the steady-state component of denotes a cosine function with a frequency of the steady-state component of , denotes a cosine function with a frequency of the steady-state component of denotes a cosine function ​ a steady-state component with a frequency of satisfies , denotes a cosine function a steady-state component with a frequency of , denotes a cosine function a steady-state component with a frequency of satisfies ; Step S14, establishing a main circuit steady-state operating point frequency domain model; According to the voltage and current relationship of the two-level converter AC / DC, the relationship between the three-phase modulation voltage steady-state vector , the DC voltage steady-state vector and the three-phase AC modulation signal steady-state vector is calculated as: (7) The AC circuit frequency domain steady-state model of the two-level converter is: (8) In the formula, The expression is: (9) In the formula, is the AC voltage steady-state vector; is the modulation voltage steady-state vector; is the AC filter inductance impedance under the steady-state frequency sequence; is the AC current steady-state vector; L f is the AC filter inductance; j is the imaginary unit; is the fundamental frequency; is the oscillation frequency; , ; wherein g is the highest iteration number considered; The expression of the DC bus frequency domain steady-state model is: (10) In the formula, , The expressions are respectively: (11) (12) In the formula, is the DC voltage steady-state matrix; is the DC current steady-state vector; is the DC capacitor steady-state vector; lis the phase sequence, a, b, c represent the three phases respectively; is the steady-state component of DC current; is the DC bus capacitor.

[0053] S2. Superimpose the AC voltage small signal component on the AC side of the two-level converter to obtain the DC voltage small signal component, determine the AC modulated voltage small signal component based on the DC voltage small signal component and the AC modulated signal steady-state component, and determine the AC current small signal component based on the AC modulated voltage small signal component and the AC voltage small signal component; determine the frequencies of the DC voltage small signal component, the AC voltage small signal component, the AC modulated voltage small signal component and the AC current small signal component respectively, and determine the frequency distribution of the small signal component transmission path based on the frequencies of the DC voltage small signal component, the AC voltage small signal component, the AC modulated voltage small signal component and the AC current small signal component; construct the DC voltage small signal matrix, the AC voltage small signal matrix, the AC current small signal matrix and the AC modulated signal small signal matrix based on the AC voltage small signal component, the AC modulated voltage small signal component, the AC current small signal component and the transmission path frequency distribution respectively, and construct the main circuit small signal component frequency domain model based on the DC voltage small signal matrix, the AC voltage small signal matrix, the AC current small signal matrix and the AC modulated signal small signal matrix.

[0054] In one embodiment, step S2 includes: Step S20: inject small signal disturbance to analyze the frequency distribution of the small signal component transmission path; superimpose a specific frequency on the AC voltage After the small signal disturbance, the DC voltage will produce a small signal response. The multiplication of the DC voltage small signal component and the AC modulated signal steady-state component will cause the AC modulated voltage to produce a small signal response. After the voltage difference between the AC modulated voltage small signal component and the AC voltage small signal component acts on the filter inductor, the AC current will produce a small signal response, thus completing one iteration of the small signal quantity transmission path; Step S201: When the two-level converter is in steady-state operation, a frequency of The sinusoidal voltage small signal disturbance, taking phase a as an example, the frequency of the small signal component of the AC voltage of phase a is The amount The frequency of the AC current in phase a is The fundamental frequency component and the frequency is The oscillation component Multiplying them will result in AC power generation frequencies of 、 According to the instantaneous power balance relationship, the DC power will generate a small signal component with a frequency of 、 a phase ac voltage small signal component with frequency , , , ; a phase ac voltage small signal component with frequency is multiplied by a phase ac current steady state component with frequency , which will result in an ac power small signal component with frequency , according to instantaneous power balance relationship, dc power will generate a small signal component with frequency , further resulting in a dc voltage small signal component with frequency ; a phase ac voltage small signal component with frequency is multiplied by a phase ac current steady state component with frequency , which will result in an ac power small signal component with frequency ; according to instantaneous power balance relationship, dc power will generate a small signal component with frequency , further resulting in a dc voltage small signal component with frequency ; step S202, according to the frequency domain relationship between the modulation voltage and the dc voltage, the small signal component with frequency in the dc voltage is multiplied by the fundamental frequency component with frequency in the a phase ac modulation signal , resulting in a small signal component with frequency in the a phase modulation voltage , the small signal component with frequency in the dc voltage is multiplied by the fundamental frequency component with frequency in the a phase ac modulation signal , resulting in a small signal component with frequency in the a phase modulation voltage ; the small signal component with frequency in the dc voltage is multiplied by the fundamental frequency component with frequency in the a phase ac modulation signal , resulting in a small signal component with frequency in the a phase modulation voltage ; the small signal component with frequency in the dc voltage is multiplied by the fundamental frequency component with frequency in the a phase ac modulation signal ;​small signal component in the DC voltage ; small signal component in the a-phase AC modulation signal ; small signal component in the a-phase modulation voltage ; small signal component in the DC voltage ; small signal component in the a-phase AC modulation signal ; small signal component in the a-phase modulation voltage ; small signal component in the DC voltage ; small signal component in the a-phase AC modulation signal ; small signal component in the a-phase modulation voltage ; ; small signal component in the DC voltage ; small signal component in the a-phase AC modulation signal ; small signal component in the a-phase modulation voltage ; small signal component in the DC voltage ; small signal component in the a-phase AC modulation signal ; small signal component in the a-phase modulation voltage ; small signal component in the a-phase modulation voltage ; small signal component in the a-phase AC voltage ; small signal component in the a-phase AC current ; small signal component in the a-phase modulation voltage ; small signal component in the a-phase AC voltage ; small signal component in the a-phase AC current ; ; small signal component in the a-phase modulation voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Small signal component of the a-phase AC voltage Step S204, the superimposed AC voltage small signal component with a frequency of After Park transformation to the dq rotating coordinate system, the AC voltage d, q-axis components and the phase-locked angle will all generate small signal components with a frequency of At the same time, the AC current d, q-axis components will also generate small signal components with a frequency of Similarly, the AC voltage d, q-axis components and the phase-locked angle will generate small signal components with a frequency of​​​​​Small signal component of , , and , and small signal component of frequency , and , while the alternating current d, q axis components will also generate small signal components of frequency , , and small signal component of frequency , ; The superimposed alternating voltage small signal component of frequency After Park transformation to the dq rotating coordinate system, the alternating voltage d, q axis components and the phase-locked angle will generate small signal components of frequency ; Therefore, the alternating current d, q axis components will also generate small signal components of frequency ; Step S205, the alternating modulation signal d, q axis components will generate small signal components of frequency , , small signal component of frequency , , and small signal component of frequency , ; After Park inverse transformation, the a-phase alternating modulation signal generates small signal components of frequency , , , small signal components of frequency , , , and small signal components of frequency , , ; The alternating modulation signal d, q axis components generate small signal components of frequency ; After Park inverse transformation, the a-phase alternating modulation signal generates small signal components of frequency , ; The above process is repeated iteratively, and finally reaches a dynamic balance; the two-level converter small signal component transmission path and frequency distribution are shown in Figure 4 ; ​​​​​​​​Step S21, according to the small signal component frequency domain characteristics, construct each small signal component frequency domain vector, for example, a phase, the small signal matrix of a phase alternating voltage can be expressed as: (13) In the formula, is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency

[0055] Therefore, the alternating voltage small signal matrix can be expressed as: (14) In the formula, is the alternating voltage small signal component with frequency is the alternating voltage small signal component with frequency The small signal matrix of a phase alternating current is respectively expressed as (15) In the formula, is the alternating current small signal component with frequency is the alternating current small signal component with frequency is the alternating current small signal component with frequency is the alternating current small signal component with frequency is the alternating current small signal component with frequency is the alternating current small signal component with frequency is the alternating current small signal component with frequency is the alternating current small signal component with frequency is the alternating current small signal component with frequency is the alternating current small signal component with frequency is the alternating current small signal component with frequency The small signal component of the AC current, The frequency is The small signal component of the AC current, The frequency is The small signal component of the AC current, The frequency is The small signal component of the AC current, The frequency is The small signal component of the AC current, The frequency is The small signal component of the AC current; Therefore, the AC current small signal matrix is ​​expressed as: (16) Where, The frequency is The small signal component of the AC current; The small signal matrices of the a-phase AC modulation signal are expressed as (17) Where, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal, The frequency is The small signal component of the AC modulated signal; Therefore, the small signal matrix of the AC modulated signal is expressed as: (18) Where, The frequency is small signal component of the AC modulation signal.

[0056] Step S22, establishing a main circuit small signal component frequency domain model; The small signal model of the two-level converter modulation voltage in the frequency domain can be expressed as (19) In the formula, is a small signal vector of the modulation voltage; The DC voltage small signal matrix can be expressed as (20) In the formula, is a small signal component of the DC voltage with a frequency of is a small signal component of the DC voltage with a frequency of is a small signal component of the DC voltage with a frequency of is a small signal component of the DC voltage with a frequency of is a small signal component of the DC voltage with a frequency of is a small signal component of the DC voltage with a frequency of is a small signal component of the DC voltage with a frequency of is a small signal component of the DC voltage with a frequency of is a small signal component of the DC voltage with a frequency of is a small signal component of the DC voltage with a frequency of The AC circuit frequency domain small signal model can be expressed as (21) In the formula, The expression is (22) The DC bus frequency domain small signal model can be expressed as (23) Wherein: (24) In the formula, is a small signal vector of the modulation voltage; km is a PWM gain; is a steady-state vector of the three-phase AC modulation signal; is a DC voltage small signal matrix; is an AC modulation signal small signal matrix; is an AC voltage small signal vector; is an AC filter inductance impedance under a small signal frequency sequence; is an AC current small signal matrix; is a DC bus capacitance admittance under a small signal frequency sequence.

[0057] In this specific application example, the VSC frequency domain characteristic analysis under the superimposed oscillation component scenario is verified. The main circuit and control parameters of the two-level converter are shown in Table 1.

[0058] Table 1 Main circuit and control parameters of two-level converter

[0059] According to steps 1 to 5, the steady-state component analysis results of the two-level converter are established. The steady-state waveform and FFT results of the AC voltage and the steady-state waveform and FFT results of the DC voltage are shown as follows: Figure 5 、 Figure 6 As shown in the figure, the AC voltage mainly contains the frequency 、 、 and The steady-state component of the DC voltage mainly contains the DC component and the frequency 、 The steady-state component of the filter inductance With filter capacitor The AC voltage steady-state waveform and FFT results, as well as the DC voltage steady-state waveform and FFT results, are completely consistent with the frequency domain characteristic analysis results.

[0060] According to steps 6 to 8, the small signal component analysis results of the two-level converter are established. The AC voltage small signal waveform and FFT results and the DC voltage small signal waveform and FFT results are shown as follows: Figure 7 、 Figure 8 As shown in the figure, the AC voltage mainly contains the frequency 、 、 、 、 and The DC voltage mainly contains a DC component and a small signal component of 、 、 、 and It can be seen that the FFT results of AC voltage and DC voltage are completely consistent with the frequency domain characteristic analysis results, which verifies the accuracy of the VSC frequency domain characteristic analysis method in a scenario with superimposed oscillation components in this patent.

[0061] Example 2 like Figure 9 As shown, based on the same inventive concept as the above embodiment, the present invention further provides a two-level converter frequency domain characteristic analysis device, wherein the two-level converter frequency domain characteristics include a steady-state operating point frequency domain model of the main circuit and a small signal component frequency domain model; the device includes: The first analysis module is used for superimposing an alternating current voltage oscillation component to an alternating current side of the two-level converter to obtain an alternating current voltage steady-state component; obtaining a transmission steady-state component according to a coupling relationship between the alternating current voltage oscillation component and an alternating current current fundamental component; determining frequencies of the alternating current voltage steady-state component and the transmission steady-state component; determining a steady-state component transmission path frequency distribution according to the frequencies of the alternating current voltage steady-state component and the transmission steady-state component; constructing a steady-state vector based on the alternating current voltage steady-state component, the transmission steady-state component and the steady-state component transmission path frequency distribution; constructing a steady-state operating point frequency domain model based on the steady-state vector; wherein the transmission steady-state component comprises a direct current voltage steady-state component, an alternating current modulation signal steady-state component and an alternating current current steady-state component. The second analysis module is used for superimposing an alternating current voltage small signal component to an alternating current side of the two-level converter to obtain a direct current voltage small signal component; determining an alternating current modulation voltage small signal component according to the direct current voltage small signal component and the alternating current modulation signal steady-state component; determining an alternating current current small signal component according to the alternating current modulation voltage small signal component and the alternating current voltage small signal component; determining frequencies of the direct current voltage small signal component, the alternating current voltage small signal component, the alternating current modulation voltage small signal component and the alternating current current small signal component respectively; determining a small signal component transmission path frequency distribution according to the frequencies of the direct current voltage small signal component, the alternating current voltage small signal component, the alternating current modulation voltage small signal component and the alternating current current small signal component; constructing a direct current voltage small signal matrix, an alternating current voltage small signal matrix, an alternating current current small signal matrix and an alternating current modulation signal small signal matrix according to the alternating current voltage small signal component, the alternating current modulation voltage small signal component, the alternating current current small signal component and the transmission path frequency distribution respectively; and constructing a main circuit small signal component frequency domain model according to the direct current voltage small signal matrix, the alternating current voltage small signal matrix, the alternating current current small signal matrix and the alternating current modulation signal small signal matrix.

[0062] Further, the steady-state operating point frequency domain model comprises: determining a relationship among a three-phase modulation voltage steady-state vector of the two-level converter, a direct current voltage steady-state vector, a three-phase alternating current modulation signal steady-state vector is:

[0063] The two-level converter alternating current loop frequency domain steady-state model is:

[0064]

[0065] In the formula, is an alternating current voltage steady-state vector; is a modulation voltage steady-state vector; is an alternating current filter inductance impedance under a steady-state frequency sequence. is the AC current steady state vector; L f is the AC filter inductance; j is the imaginary unit; is the fundamental frequency; is the oscillation frequency; , where g is the maximum number of iterations considered; DC bus frequency domain steady state model:

[0066]

[0067]

[0068] where, is the DC voltage steady state matrix; is the DC current steady state vector; is the DC capacitor steady state vector; l is the phase sequence, a, b, c represent three phases respectively; is the DC current steady state component; is the DC bus capacitor.

[0069] Further, the main circuit small signal component frequency domain model, including: two-level converter modulation voltage frequency domain small signal model:

[0070] AC circuit frequency domain small signal model:

[0071]

[0072] DC bus frequency domain small signal model:

[0073]

[0074] where, is the modulation voltage small signal vector; K m is the PWM gain; is the three-phase AC modulation signal steady state vector; is the DC voltage small signal matrix; is the AC modulation signal small signal matrix; is the AC voltage small signal vector; is the AC filter inductance impedance under small signal frequency sequence; for the small-signal matrix of the AC current; for the small-signal frequency sequence of the DC bus capacitor admittance.

[0075] Embodiment 3 As Figure 10 The present application also provides an electronic device 100 for implementing the above-mentioned two-level converter frequency domain characteristic analysis method. The electronic device 100 comprises a memory 101, at least one processor 102, a computer program 103 stored in the memory 101 and executable on the at least one processor 102, and at least one communication bus 104.

[0076] The memory 101 can be used to store the computer program 103, and the processor 102 can implement the steps of the two-level converter frequency domain characteristic analysis method of embodiment 1 by running or executing the computer program stored in the memory 101 and calling the data stored in the memory 101.

[0077] The memory 101 can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system, at least one application program required by a function (such as a sound playing function, an image playing function, etc.), etc.; and the data storage area can store data (such as audio data) created according to the use of the electronic device 100, etc. In addition, the memory 101 can include a non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device.

[0078] The at least one processor 102 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The processor 102 can be a microprocessor or can also be any conventional processor, etc. The processor 102 is the control center of the electronic device 100, and connects all parts of the electronic device 100 through various interfaces and lines.

[0079] The memory 101 in the electronic device 100 stores a plurality of instructions to implement a two-level converter frequency domain characteristic analysis method, and the processor 102 can execute the plurality of instructions to implement: An AC voltage oscillation component is superimposed on the AC side of the two-level converter to obtain an AC voltage steady-state component; a transfer steady-state component is obtained according to the coupling relationship between the AC voltage oscillation component and the AC current fundamental component; the frequencies of the AC voltage steady-state component and the transfer steady-state component are determined, and the steady-state component transfer path frequency distribution is determined according to the frequencies of the AC voltage steady-state component and the transfer steady-state component; based on the AC voltage steady-state component, the transfer steady-state component and the steady-state component transfer path frequency distribution, a steady-state vector is constructed; a steady-state operating point frequency domain model is constructed based on the steady-state vector; wherein the transfer steady-state component includes a DC voltage steady-state component, an AC modulation signal steady-state component and an AC current steady-state component; an AC voltage small signal component is superimposed on the AC side of the two-level converter to obtain a DC voltage small signal component, an AC modulation voltage small signal component is determined according to the DC voltage small signal component and the AC modulation signal steady-state component, and an AC current small signal component is determined according to the AC modulation voltage small signal component and the AC voltage small signal component; The frequencies of the AC voltage small signal component, the AC modulation voltage small signal component and the AC current small signal component are determined respectively, and the small signal component transfer path frequency distribution is determined according to the frequencies of the AC voltage small signal component, the AC modulation voltage small signal component and the AC current small signal component; according to the AC voltage small signal component, the AC modulation voltage small signal component, the AC current small signal component and the transfer path frequency distribution, an AC voltage small signal matrix, an AC current small signal matrix and an AC modulation signal small signal matrix are constructed respectively, and a main circuit small signal component frequency domain model is constructed according to the AC voltage small signal matrix, the AC current small signal matrix and the AC modulation signal small signal matrix.

[0080] Embodiment 4 If the modules / units integrated in the electronic device 100 are implemented in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware. The computer program can be stored in a computer readable storage medium, and when the processor executes the computer program, the steps of the above-mentioned various method embodiments can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms. The computer readable medium can include any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory and read-only memory (ROM).

[0081] Those skilled in the art will appreciate that embodiments of the present application can be devised for a method, a system, or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer readable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code thereon.

[0082] The present application is described in reference to the flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0083] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0084] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams. Figure 1 one or more functions specified in the flowchart illustrations and / or block diagrams.

[0085] In this description, references to "one embodiment", "an example", "a specific example", etc., mean that a particular feature, structure, material, or characteristic being referred to is included in at least one embodiment or example of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0086] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit it. Although the present application has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the specific embodiments of the present application can be modified or equivalently replaced without departing from the spirit and scope of the present application, and any modification or equivalent replacement should be covered within the protection scope of the claims of the present application.

Claims

1. A method for analyzing the frequency domain characteristics of a two-level converter, characterized in that: The frequency domain characteristics of the two-level converter include a steady-state operating point frequency domain model of the main circuit and a small signal component frequency domain model; the method includes: An AC voltage oscillation component is superimposed on the AC side of the two-level converter to obtain an AC voltage steady-state component; a transfer steady-state component is obtained based on the coupling relationship between the AC voltage oscillation component and the AC current fundamental frequency component; the frequencies of the AC voltage steady-state component and the transfer steady-state component are determined, and the frequency distribution of the steady-state component transfer path is determined based on the frequencies of the AC voltage steady-state component and the transfer steady-state component; a steady-state vector is constructed based on the AC voltage steady-state component, the transfer steady-state component, and the frequency distribution of the steady-state component transfer path; a steady-state operating point frequency domain model is constructed based on the steady-state vector; wherein the transfer steady-state component includes a DC voltage steady-state component, an AC modulation signal steady-state component, and an AC current steady-state component; An AC voltage small signal component is superimposed on the AC side of the two-level converter to obtain a DC voltage small signal component. The AC modulated voltage small signal component is determined based on the DC voltage small signal component and the steady-state component of the AC modulated signal. The AC current small signal component is determined based on the AC modulated voltage small signal component and the AC voltage small signal component. The frequencies of the DC voltage small signal component, the AC voltage small signal component, the AC modulated voltage small signal component and the AC current small signal component are determined respectively. The frequency distribution of the small signal component transmission path is determined based on the frequencies of the DC voltage small signal component, the AC voltage small signal component, the AC modulated voltage small signal component and the AC current small signal component. Based on the AC voltage small signal component, the AC modulated voltage small signal component, the AC current small signal component and the transmission path frequency distribution, a DC voltage small signal matrix, an AC voltage small signal matrix, an AC current small signal matrix and an AC modulated signal small signal matrix are constructed respectively. A frequency domain model of the main circuit small signal component is constructed based on the DC voltage small signal matrix, the AC voltage small signal matrix, the AC current small signal matrix and the AC modulated signal small signal matrix.

2. The method for analyzing the frequency domain characteristics of a two-level converter according to claim 1, wherein: Steady-state operating point frequency domain model, including: Determine the steady-state vector of three-phase modulation voltage of two-level converter , DC voltage steady-state vector , steady-state vector of three-phase AC modulation signal The relationship between them is: Frequency domain steady-state model of the two-level converter AC circuit: Where, is the steady-state AC voltage vector; is the steady-state vector of the modulation voltage; is the AC filter inductor impedance under steady-state frequency sequence; is the steady-state vector of AC current; L f is the AC filter inductor; j is the imaginary unit; is the fundamental frequency; is the oscillation frequency; , ,in g is the highest number of iterations considered; DC bus frequency domain steady-state model: Where, is the DC voltage steady-state matrix; is the DC current steady-state vector; is the DC capacitance steady-state vector; l is the phase sequence, a, b, c represent the three phases respectively; is the steady-state component of DC current; is the DC bus capacitor.

3. The method for analyzing the frequency domain characteristics of a two-level converter according to claim 1, wherein: The steady-state vectors include the AC current steady-state vector, the DC voltage steady-state vector, the AC modulated signal steady-state vector and the AC voltage steady-state vector.

4. The method for analyzing the frequency domain characteristics of a two-level converter according to claim 2, wherein: The AC voltage small signal matrix is ​​expressed as: Where, The frequency is The small signal component of the AC voltage; The AC current small signal matrix is ​​expressed as: Where, The frequency is The small signal component of the AC current; The small signal matrix of the AC modulated signal is expressed as: Where, The frequency is The small signal component of the AC modulated signal.

5. The method for analyzing the frequency domain characteristics of a two-level converter according to claim 4, wherein: Frequency domain model of the main circuit small signal component, including: Frequency domain small signal model of two-level converter modulation voltage: AC circuit frequency domain small signal model: DC bus frequency domain small signal model: Where, is the modulation voltage small signal vector; K m is the PWM gain; is the steady-state vector of the three-phase AC modulation signal; is the DC voltage small signal matrix; is the small signal matrix of AC modulated signal; is the AC voltage small signal vector; is the AC filter inductor impedance under small signal frequency sequence; is the AC current small signal matrix; is the DC bus capacitance admittance under small signal frequency sequence.

6. A two-level converter frequency domain characteristic analysis device, characterized in that: The frequency domain characteristics of the two-level converter include a steady-state operating point frequency domain model of the main circuit and a small signal component frequency domain model; the device includes: The first analysis module is configured to superimpose an AC voltage oscillation component onto the AC side of the two-level converter to obtain an AC voltage steady-state component; obtain a transfer steady-state component based on the coupling relationship between the AC voltage oscillation component and the AC current fundamental frequency component; determine the frequencies of the AC voltage steady-state component and the transfer steady-state component, and determine the frequency distribution of the steady-state component transfer path based on the frequencies of the AC voltage steady-state component and the transfer steady-state component; construct a steady-state vector based on the AC voltage steady-state component, the transfer steady-state component, and the frequency distribution of the steady-state component transfer path; and construct a steady-state operating point frequency domain model based on the steady-state vector; wherein the transfer steady-state component includes a DC voltage steady-state component, an AC modulation signal steady-state component, and an AC current steady-state component. The second analysis module is used to superimpose an AC voltage small signal component on the AC side of the two-level converter to obtain a DC voltage small signal component, determine the AC modulated voltage small signal component based on the DC voltage small signal component and the AC modulated signal steady-state component, and determine the AC current small signal component based on the AC modulated voltage small signal component and the AC voltage small signal component; determine the frequencies of the DC voltage small signal component, the AC voltage small signal component, the AC modulated voltage small signal component, and the AC current small signal component respectively, and determine the frequency distribution of the small signal component transmission path based on the frequencies of the DC voltage small signal component, the AC voltage small signal component, the AC modulated voltage small signal component, and the AC current small signal component; construct a DC voltage small signal matrix, an AC voltage small signal matrix, an AC current small signal matrix, and an AC modulated signal small signal matrix based on the AC voltage small signal component, the AC modulated voltage small signal component, the AC current small signal component, and the transmission path frequency distribution; and construct a main circuit small signal component frequency domain model based on the DC voltage small signal matrix, the AC voltage small signal matrix, the AC current small signal matrix, and the AC modulated signal small signal matrix.

7. The two-level converter frequency domain characteristic analysis device according to claim 6, characterized in that: Steady-state operating point frequency domain model, including: Determine the steady-state vector of three-phase modulation voltage of two-level converter , DC voltage steady-state vector , steady-state vector of three-phase AC modulation signal The relationship between them is: Frequency domain steady-state model of the two-level converter AC circuit: Where, is the steady-state AC voltage vector; is the steady-state vector of the modulation voltage; is the AC filter inductor impedance under steady-state frequency sequence; is the steady-state vector of AC current; L f is the AC filter inductor; j is the imaginary unit; is the fundamental frequency; is the oscillation frequency; , ,in g is the highest number of iterations considered; DC bus frequency domain steady-state model: Where, is the DC voltage steady-state matrix; is the DC current steady-state vector; is the DC capacitance steady-state vector; l is the phase sequence, a, b, c represent the three phases respectively; is the steady-state component of DC current; is the DC bus capacitor.

8. The two-level converter frequency domain characteristic analysis device according to claim 7, characterized in that: Frequency domain model of the main circuit small signal component, including: Frequency domain small signal model of two-level converter modulation voltage: AC circuit frequency domain small signal model: DC bus frequency domain small signal model: Where, is the modulation voltage small signal vector; K m is the PWM gain; is the steady-state vector of the three-phase AC modulation signal; is the DC voltage small signal matrix; is the small signal matrix of AC modulated signal; is the AC voltage small signal vector; is the AC filter inductor impedance under small signal frequency sequence; is the AC current small signal matrix; is the DC bus capacitance admittance under small signal frequency sequence.

9. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the processor is configured to execute a computer program stored in the memory to implement the method for analyzing the frequency domain characteristics of a two-level converter according to any one of claims 1 to 5.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores at least one instruction, and when the at least one instruction is executed by a processor, the method for analyzing frequency domain characteristics of a two-level converter according to any one of claims 1 to 5 is implemented.

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