An analysis method and device for high-frequency impedance characteristics of a VSC

Abstract

The application provides a kind of analysis method and device for VSC high frequency band impedance characteristic, comprising, the disturbance voltage and disturbance current of target VSC are collected, and sampling voltage and sampling current are determined respectively;Determine the corresponding PWM modulation signal of the frequency component of the PWM sideband;Determine the frequency coupling coefficient between each frequency;Determine the VSC port voltage corresponding to the frequency component according to the frequency coupling coefficient;When VSC port sampling filter, determine the VSC port current of the time;Judge whether the difference between the amplitude and phase value of the VSC port current of the time and the amplitude and phase value of the VSC port current of the previous time meets the preset error allowable value;If not, then determine the VSC port current of the next time again;If satisfied, then calculate the VSC input impedance according to the VSC port current of the time and the corresponding disturbance voltage.The application considers the influence of sampling and PWM sideband effect frequency coupling effect on VSC impedance characteristic, and improves the analysis accuracy of VSC high frequency band impedance characteristic above Nyquist frequency.

Description

Technical Field

[0001] This invention relates to the field of VSC high-frequency impedance characteristic analysis technology, and in particular to a method and apparatus for analyzing VSC high-frequency impedance characteristics. Background Technology

[0002] With the rapid development of new power systems characterized by high proportions of new energy sources and power electronic devices, voltage source converters (VSCs) are widely used as key port devices in scenarios such as AC / DC distribution network interconnection, new energy grid-connected operation, and energy storage access. However, the interaction between the VSC port impedance characteristics based on high-bandwidth closed-loop controllers and capacitive and inductive components such as cabled distribution lines, reactive power compensation equipment, and various equipment port filters leads to a widening of the system's inherent resonant point distribution. This significantly increases the probability of overlap with high-frequency harmonics generated by the switching actions of different types of power electronic devices, resulting in increasingly severe high-frequency resonance risks in the distribution network. Establishing a VSC impedance characteristic model applicable to the mid-to-high frequency range is essential for the analysis of distribution network resonance characteristics and stability.

[0003] Considering the frequency coupling effect of sampling sideband harmonics and PWM (Pulse Width Modulation) sideband harmonics in impedance characteristic analysis is an important way to improve the accuracy of impedance characteristic analysis in the high-frequency band of VSC. Most existing impedance characteristic analysis methods ignore the coupling effect of sampling and PWM sideband harmonics, and only a few studies consider the influence of sampling sideband harmonics or PWM sideband harmonics alone. There is a lack of accurate analysis methods for the high-frequency impedance characteristics of VSC that simultaneously consider the frequency coupling effects of sampling and PWM sideband harmonics. Summary of the Invention

[0004] The purpose of this invention is to propose a method and apparatus for analyzing the impedance characteristics of VSC in the high-frequency band, addressing the technical problem of accurately analyzing the impedance characteristics of VSC in the high-frequency band while simultaneously considering the effects of sampling and PWM sideband harmonic frequency coupling.

[0005] On the one hand, an analytical method for the impedance characteristics of VSC in the high-frequency band is provided, including:

[0006] The disturbance voltage and disturbance current of the target VSC are collected, and the sampling voltage and sampling current are determined according to the disturbance voltage and the disturbance current, respectively. The disturbance current includes at least the current disturbance frequency component, the sampling sideband frequency component and the PWM sideband frequency component generated at the VSC port under the disturbance voltage excitation.

[0007] The PWM modulation signal corresponding to the multiple frequency components of the PWM sideband is determined based on the sampling voltage and the sampling current.

[0008] The frequency coupling coefficient between each frequency is determined based on the sampling voltage, the sampling current, and the PWM modulation signal.

[0009] The VSC port voltage corresponding to the frequency component is determined based on the frequency coupling coefficient.

[0010] The VSC port current is determined based on the VSC port voltage and VSC port filter parameters.

[0011] Determine whether the difference between the amplitude and phase of the current VSC port current and the amplitude and phase of the previous VSC port current meets the preset error allowable value; if not, re-acquire the disturbance voltage and disturbance current of the target VSC and redetermine the next VSC port current; if it meets the requirement, calculate the VSC input impedance based on the current VSC port current and the corresponding disturbance voltage.

[0012] Preferably, the sampling voltage and sampling current are determined according to the following calculation formulas:

[0013]

[0014]

[0015] in, These represent the sampling voltages corresponding to the three frequencies; These represent the sampling currents corresponding to the three frequencies; This indicates that the frequency of the VSC grid connection point is f. p Small disturbance voltage; Indicates the frequency components of the disturbance; Represents the sideband frequency components; This indicates the PWM sideband frequency component; * represents phasor conjugation operation.

[0016] Preferably, the PWM modulation signal corresponding to the multiple frequency components of the PWM sideband is determined according to the following calculation formula:

[0017]

[0018] in, This represents the PWM modulation signal corresponding to the three frequency components; k ip Indicates the proportionality coefficient of the inner current loop; k ii K represents the integral coefficient of the inner current loop; d ω represents the dq-axis coupling coefficient; p ω p1 ω p2 ω0 and ω0 represent the injected perturbation angular frequency, the sampling sideband component angular frequency, the PWM sideband component angular frequency, and the fundamental angular frequency, respectively; GI This represents the controller current inner loop transfer function.

[0019] Preferably, the frequency coupling coefficient between each frequency is determined according to the following calculation formula:

[0020]

[0021] Among them, K vp K vp1 K vp2 They represent ω respectively p ω p1 ω p2 The PWM modulation gain coefficient between the frequency component of the modulation signal and the port voltage at the same frequency; K cp Represents ω p Frequency modulation signal and ω p2 Frequency coupling coefficient between frequency port voltages; K cp2 Represents ω p2 Frequency modulation signal and ω p Frequency coupling coefficient between frequency port voltages; ω p ω p1 ω p2 ω c These represent the injected disturbance angular frequency, the sampling sideband component angular frequency, the PWM sideband component angular frequency, and the switching angular frequency, respectively; T s Indicate the sampling time interval, M0 and θ M0 M represents the amplitude and phase angle of the fundamental component in the modulated signal, respectively; p M p2 These represent the amplitudes of the perturbation frequency component and the PWM sideband frequency component in the modulated signal, respectively; J i This represents the first type of Bessel function.

[0022] Preferably, the VSC port voltage corresponding to the frequency component is determined according to the following calculation formula:

[0023]

[0024] in, These represent the VSC port voltages corresponding to the three frequency components; G d This represents the equivalent transfer function of the controller delay effect.

[0025] Preferably, the VSC port current is determined based on the VSC port voltage using the following calculation formula:

[0026]

[0027] in, These represent the three frequency components corresponding to the VSC port current at that time; Yf This represents the filter transfer function.

[0028] Preferably, the VSC input impedance is calculated according to the following formula:

[0029]

[0030] Where Z1 represents the VSC input impedance when the VSC port is sampled by the filter; This indicates the component of the VSC port current in the current cycle; This indicates that the frequency of the VSC grid connection point is f. p Small disturbance voltage.

[0031] Preferably, it further includes:

[0032] When sampling and PWM sideband harmonic frequency coupling are not considered, the VSC input impedance is calculated using the following formula:

[0033]

[0034] Where Z2 represents the VSC input impedance when sampling and PWM sideband harmonic frequency coupling are not considered; Y f G represents the filter transfer function; d ω represents the equivalent transfer function of the controller delay effect; p Indicates the injected perturbation angular frequency; K vp Represents ω p The PWM modulation gain coefficient between the frequency component modulation signal and the port voltage at the same frequency.

[0035] On the other hand, an analysis device for the impedance characteristics of VSC in the high-frequency band is also provided to implement the method, including:

[0036] The voltage and current acquisition module is used to acquire the disturbance voltage and disturbance current of the target VSC, and determine the sampling voltage and sampling current according to the disturbance voltage and disturbance current respectively. The disturbance current includes at least the current disturbance frequency component, the sampling sideband frequency component and the PWM sideband frequency component generated at the VSC port under the disturbance voltage excitation.

[0037] The PWM modulation signal calculation module is used to determine the PWM modulation signal corresponding to multiple frequency components of the PWM sideband based on the sampling voltage and the sampling current.

[0038] The coupling coefficient calculation module is used to determine the frequency coupling coefficient between each frequency based on the sampling voltage, the sampling current and the PWM modulation signal;

[0039] A port voltage module is used to determine the VSC port voltage corresponding to the frequency component based on the frequency coupling coefficient.

[0040] The input impedance calculation module is used to determine the current VSC port current based on the VSC port voltage and the VSC port filter parameters.

[0041] Determine whether the difference between the amplitude and phase of the current VSC port current and the amplitude and phase of the previous VSC port current meets the preset error allowable value; if not, re-acquire the disturbance voltage and disturbance current of the target VSC and redetermine the next VSC port current; if it meets the requirement, calculate the VSC input impedance based on the current VSC port current and the corresponding disturbance voltage.

[0042] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0043] The present invention provides a method and apparatus for analyzing the impedance characteristics of VSC in the high-frequency band. Considering the influence of frequency-frequency coupling effect on the impedance characteristics of VSC when sampling and PWM sideband effects work together, the proposed analysis method can improve the analysis accuracy of the impedance characteristics of VSC in the high-frequency band above the Nyquist frequency. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0045] Figure 1 This is a schematic diagram of a VSC structure in an embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram of a VSC current inner loop control in an embodiment of the present invention.

[0047] Figure 3 This is a schematic diagram of the main flow of an analysis method for the impedance characteristics of VSC in the high-frequency band according to an embodiment of the present invention.

[0048] Figure 4 This is a logic diagram of an analysis method for the impedance characteristics of VSC in the high-frequency band, as described in an embodiment of the present invention.

[0049] Figure 5 This is a schematic diagram showing the comparison of impedance amplitudes corresponding to different analysis methods in the embodiments of the present invention.

[0050] Figure 6This is a schematic diagram showing the comparison results of impedance phase angles corresponding to different analysis methods in the embodiments of the present invention.

[0051] Figure 7 This is a schematic diagram of an analysis device for the impedance characteristics of VSC in the high-frequency band, as described in an embodiment of the present invention. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0053] like Figure 1 and Figure 2 As shown in the schematic diagram of the VSC structure provided in this application, the VSC controller sampling frequency is f. s The switching frequency is f c =f s The fundamental frequency is f0. Assume the VSC grid connection point has a frequency of f. p The small perturbation voltage is expressed in phasor form. Under disturbance voltage excitation, the current generated at the VSC port contains the disturbance frequency f. p Sampling sideband component f s -f p and PWM sideband component f c -f p The three frequency components, +f0, are represented in phasor form and are respectively set as follows: Configure to meet requirements The initial values ​​of amplitude and phase, and the allowable values ​​for calculation error.

[0054] like Figure 3 and Figure 4 The diagram shown is a schematic representation of an embodiment of a method for analyzing the impedance characteristics of VSC in the high-frequency band provided by the present invention. In this embodiment, the method includes the following steps:

[0055] The disturbance voltage and disturbance current of the target VSC are acquired, and the sampling voltage and sampling current are determined based on the disturbance voltage and disturbance current, respectively. The disturbance current includes at least the current disturbance frequency component, the sampling sideband frequency component, and the PWM sideband frequency component generated at the VSC port under disturbance voltage excitation. Understandably, considering the frequency coupling effect caused by sampling, the sampling voltage obtained after sampling the disturbance voltage and disturbance current is calculated according to the formula. and and sampling current

[0056] In this embodiment, the sampling voltage and sampling current are determined according to the following calculation formulas:

[0057]

[0058]

[0059] in, These represent the sampling voltages corresponding to the three frequencies; These represent the sampling currents corresponding to the three frequencies; This indicates that the frequency of the VSC grid connection point is f. p Small disturbance voltage; Indicates the frequency components of the disturbance; Represents the sideband frequency components; This indicates the PWM sideband frequency component; * represents phasor conjugation operation.

[0060] Furthermore, the PWM modulation signal corresponding to multiple frequency components of the PWM sideband is determined based on the sampled voltage and the sampled current; understandably, the influence of the phase-locked loop and voltage outer loop in the VSC controller is ignored, based on Figure 2 The control loop block diagram shown is used to calculate the PWM modulation signals corresponding to the three frequency components.

[0061] In this embodiment, the PWM modulation signal corresponding to multiple frequency components of the PWM sideband is determined according to the following calculation formula:

[0062]

[0063] in, This represents the PWM modulation signal corresponding to the three frequency components; k ip Indicates the proportionality coefficient of the inner current loop; k ii K represents the integral coefficient of the inner current loop; d ω represents the dq-axis coupling coefficient; p ω p1 ω p2 ω0 and ω0 represent the injected perturbation angular frequency, the sampling sideband component angular frequency, the PWM sideband component angular frequency, and the fundamental angular frequency, respectively; G I This represents the controller current inner loop transfer function.

[0064] Furthermore, the frequency coupling coefficient between each frequency is determined based on the sampling voltage, the sampling current, and the PWM modulation signal; understandably, the frequency coupling coefficient between different frequencies is calculated considering the influence of PWM sideband effects.

[0065] In this embodiment, the frequency coupling coefficient between each frequency is determined according to the following calculation formula:

[0066]

[0067] Among them, Kvp K vp1 K vp2 They represent ω respectively p ω p1 ω p2 The PWM modulation gain coefficient between the frequency component of the modulation signal and the port voltage at the same frequency; K cp Represents ω p Frequency modulation signal and ω p2 Frequency coupling coefficient between frequency port voltages; K cp2 Represents ω p2 Frequency modulation signal and ω p Frequency coupling coefficient between frequency port voltages; ω p ω p1 ω p2 ω c These represent the injected disturbance angular frequency, the sampling sideband component angular frequency, the PWM sideband component angular frequency, and the switching angular frequency, respectively; T s Indicate the sampling time interval, M0 and θ M0 M represents the amplitude and phase angle of the fundamental component in the modulated signal, respectively; p M p2 These represent the amplitudes of the perturbation frequency component and the PWM sideband frequency component in the modulated signal, respectively; J i This represents the first type of Bessel function.

[0068] Furthermore, the VSC port voltage corresponding to the frequency component is determined based on the frequency coupling coefficient; understandably, the VSC port voltage corresponding to the three frequency components is calculated according to the frequency coupling relationship based on the frequency coupling coefficient in the previous step.

[0069] In this embodiment, the VSC port voltage corresponding to the frequency component is determined according to the following calculation formula:

[0070]

[0071] in, These represent the VSC port voltages corresponding to the three frequency components; G d This represents the equivalent transfer function of the controller delay effect.

[0072] Furthermore, the VSC port current is determined based on the VSC port voltage and VSC port filter parameters; it is then determined whether the difference between the amplitude and phase of the current VSC port current and the amplitude and phase of the previous VSC port current meets a preset error tolerance value; if not, the disturbance voltage and disturbance current of the target VSC are re-acquired, and the next VSC port current is re-determined; if so, the VSC input impedance is calculated based on the current VSC port current and the corresponding disturbance voltage. Understandably, the determination... The amplitude and phase values ​​are the same as those obtained in the previous calculation. Check whether the differences between the corresponding amplitude and phase values ​​meet the allowable error values. If not, repeat the above steps; if they do meet, then use the final VSC port current... Components and grid connection point disturbance voltage The input impedance of VSC is calculated.

[0073] In this embodiment, the VSC port current is determined based on the VSC port voltage using the following calculation formula:

[0074]

[0075] in, These represent the three frequency components corresponding to the VSC port current at that time; Y f This represents the filter transfer function.

[0076] More specifically, the VSC input impedance is calculated using the following formula:

[0077]

[0078] This indicates the component of the VSC port current in the current cycle; This indicates that the frequency of the VSC grid connection point is f. p Small disturbance voltage.

[0079] In another embodiment, when sampling and PWM sideband harmonic frequency coupling are not considered, the VSC input impedance is calculated according to the following formula:

[0080]

[0081] Where Z2 represents the VSC input impedance when sampling and PWM sideband harmonic frequency coupling are not considered; Y f G represents the filter transfer function; d ω represents the equivalent transfer function of the controller delay effect; p Indicates the injected perturbation angular frequency; K vp Represents ω pThe PWM modulation gain coefficient between the frequency component modulation signal and the port voltage at the same frequency.

[0082] In a specific embodiment, for the VSC parameters shown in Table 1, a VSC model is built in electromagnetic transient simulation software. The amplitude and phase of the VSC input impedance at different frequency points are obtained by frequency scanning, and compared with the impedance characteristic analysis results considering the frequency coupling of sideband components proposed in this invention and the traditional impedance analysis results not considering the frequency coupling of sideband components.

[0083] Table 1. Main parameters of VSC circuit and control

[0084]

[0085]

[0086] Figure 5 This is a comparison of the VSC input impedance amplitude above the Nyquist frequency. In other words, it is a comparison of the VSC impedance characteristic analysis results considering sampling and PWM sideband component frequency coupling, the VSC impedance characteristic analysis results without considering frequency coupling, and the electromagnetic transient simulation results regarding impedance amplitude. Figure 6 This paper presents a comparison of the phase of the VSC input impedance above the Nyquist frequency. Specifically, it compares the impedance characteristic analysis results considering sampling and PWM sideband component frequency coupling with the electromagnetic transient simulation results regarding the impedance phase angle. The high-frequency impedance characteristic analysis results of the VSC proposed in this invention are almost identical to the simulation results, proving the correctness of the proposed high-frequency impedance characteristic analysis method for VSC considering the coupling effect of sampling and PWM sideband components. Compared with the analysis method that does not consider sampling and PWM sideband component frequency coupling, it can be seen that the high-frequency impedance characteristic analysis method for VSC proposed in this invention can more accurately reflect the VSC impedance characteristics.

[0087] like Figure 7 As shown, another embodiment of the present invention also provides an analysis apparatus for the impedance characteristics of VSC in the high-frequency band, for implementing the analysis method for the impedance characteristics of VSC in the high-frequency band, including:

[0088] The voltage and current acquisition module is used to acquire the disturbance voltage and disturbance current of the target VSC, and determine the sampling voltage and sampling current according to the disturbance voltage and disturbance current respectively. The disturbance current includes at least the current disturbance frequency component, the sampling sideband frequency component and the PWM sideband frequency component generated at the VSC port under the disturbance voltage excitation.

[0089] The PWM modulation signal calculation module is used to determine the PWM modulation signal corresponding to multiple frequency components of the PWM sideband based on the sampling voltage and the sampling current.

[0090] The coupling coefficient calculation module is used to determine the frequency coupling coefficient between each frequency based on the sampling voltage, the sampling current and the PWM modulation signal;

[0091] A port voltage module is used to determine the VSC port voltage corresponding to the frequency component based on the frequency coupling coefficient.

[0092] The input impedance calculation module is used to determine the current VSC port current based on the VSC port voltage and the VSC port filter parameters.

[0093] Determine whether the difference between the amplitude and phase of the current VSC port current and the amplitude and phase of the previous VSC port current meets the preset error allowable value; if not, re-acquire the disturbance voltage and disturbance current of the target VSC and redetermine the next VSC port current; if it meets the requirement, calculate the VSC input impedance based on the current VSC port current and the corresponding disturbance voltage.

[0094] It should be noted that the apparatus described in the above embodiments corresponds to the method described in the above embodiments. Therefore, the parts of the apparatus described in the above embodiments that are not described in detail can be obtained by referring to the content of the method described in the above embodiments, and will not be repeated here.

[0095] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0096] The present invention provides a method and apparatus for analyzing the impedance characteristics of VSC in the high-frequency band. Considering the influence of frequency-frequency coupling effect on the impedance characteristics of VSC when sampling and PWM sideband effects work together, the proposed analysis method can improve the analysis accuracy of the impedance characteristics of VSC in the high-frequency band above the Nyquist frequency.

[0097] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for analyzing the impedance characteristics of VSC in the high-frequency band, characterized in that, include: The disturbance voltage and disturbance current of the target VSC are collected, and the sampling voltage and sampling current are determined according to the disturbance voltage and the disturbance current, respectively. The disturbance current includes at least the current disturbance frequency component, the sampling sideband frequency component and the PWM sideband frequency component generated at the VSC port under the disturbance voltage excitation. The PWM modulation signal corresponding to the multiple frequency components of the PWM sideband is determined based on the sampling voltage and the sampling current. The frequency coupling coefficient between each frequency is determined based on the sampling voltage, the sampling current, and the PWM modulation signal. The VSC port voltage corresponding to the frequency component is determined based on the frequency coupling coefficient. The VSC port current is determined based on the VSC port voltage and VSC port filter parameters. Determine whether the difference between the amplitude and phase of the current VSC port current and the amplitude and phase of the previous VSC port current meets the preset error allowable value. If the conditions are not met, the disturbance voltage and disturbance current of the target VSC are re-acquired, and the VSC port current for the next time is determined. If the conditions are met, the VSC input impedance is calculated based on the current VSC port current and the corresponding disturbance voltage.

2. The method as described in claim 1, characterized in that, The sampling voltage and sampling current are determined according to the following calculation formulas: in, , , These represent the sampling voltages corresponding to the three frequencies; , , These represent the sampling currents corresponding to the three frequencies; This indicates that the frequency of VSC grid connection points is [missing information]. f p Small disturbance voltage; Indicates the frequency components of the disturbance; Indicates the sampled sideband frequency components; Indicates the frequency components of the PWM sideband; This represents the phasor conjugate operation.

3. The method as described in claim 2, characterized in that, The PWM modulation signal corresponding to the various frequency components of the PWM sideband is determined according to the following calculation formula: in, , , This represents the PWM modulation signal corresponding to the three frequency components. k ip Indicates the proportionality coefficient of the inner current loop; k ii Indicates the integral coefficient of the inner current loop; K d Indicates the coupling coefficient between the d and q axes; , , , These represent the injected disturbance angular frequency, the sampling sideband component angular frequency, the PWM sideband component angular frequency, and the fundamental angular frequency, respectively. This represents the controller current inner loop transfer function.

4. The method as described in claim 3, characterized in that, The frequency coupling coefficient between each frequency is determined using the following formula: in, , , They represent , , The PWM modulation gain coefficient between the frequency component of the modulation signal and the port voltage at the same frequency; express ω p Frequency modulation signal and ω p2 Frequency coupling coefficient between frequency port voltages; express ω p2 Frequency modulation signal and ω p Frequency coupling coefficient between frequency port voltages; Indicates the equivalent gain of PWM modulation; , , , These represent the injected disturbance angular frequency, the sampling sideband component angular frequency, the PWM sideband component angular frequency, and the switching angular frequency, respectively. T s Indicates the sampling time interval. M 0 and θ M0 These represent the amplitude and phase angle of the fundamental component in the modulated signal, respectively. M p , M p2 These represent the amplitudes of the disturbance frequency component and the PWM sideband frequency component in the modulated signal, respectively. J i This represents the first type of Bessel function.

5. The method as described in claim 4, characterized in that, The VSC port voltage corresponding to the frequency component is determined using the following formula: in, , , These represent the VSC port voltages corresponding to the three frequency components, respectively. This represents the equivalent transfer function of the controller delay effect.

6. The method as described in claim 5, characterized in that, The VSC port current is determined based on the VSC port voltage using the following formula: in, , , These represent the three frequency components corresponding to the VSC port current at that time. Y f This represents the filter transfer function.

7. The method as described in claim 6, characterized in that, The VSC input impedance is calculated using the following formula: in, This indicates the VSC input impedance when a sampling filter is set at the VSC port; This indicates the component of the VSC port current in the current cycle; This indicates that the frequency of VSC grid connection points is [missing information]. f p Small disturbance voltage.

8. The method according to any one of claims 1-7, characterized in that, Also includes: When frequency coupling between the sampling sideband harmonics and the PWM sideband harmonics is not considered, the VSC input impedance is calculated using the following formula: in, This represents the VSC input impedance when the frequency coupling between the sampling sideband harmonics and the PWM sideband harmonics is not considered. Y f Represents the filter transfer function; Represents the equivalent transfer function of the controller delay effect; Indicates the angular frequency of the injected disturbance; express The PWM modulation gain coefficient between the frequency component modulation signal and the port voltage at the same frequency.

9. An analysis device for the impedance characteristics of VSC in the high-frequency band, used to implement the method as described in any one of claims 1-8, characterized in that, include: The voltage and current acquisition module is used to acquire the disturbance voltage and disturbance current of the target VSC, and determine the sampling voltage and sampling current according to the disturbance voltage and disturbance current respectively. The disturbance current includes at least the current disturbance frequency component, the sampling sideband frequency component and the PWM sideband frequency component generated at the VSC port under the disturbance voltage excitation. The PWM modulation signal calculation module is used to determine the PWM modulation signal corresponding to multiple frequency components of the PWM sideband based on the sampling voltage and the sampling current. The coupling coefficient calculation module is used to determine the frequency coupling coefficient between each frequency based on the sampling voltage, the sampling current and the PWM modulation signal; A port voltage module is used to determine the VSC port voltage corresponding to the frequency component based on the frequency coupling coefficient. The input impedance calculation module is used to determine the current VSC port current based on the VSC port voltage and the VSC port filter parameters. Determine whether the difference between the amplitude and phase of the current VSC port current and the amplitude and phase of the previous VSC port current meets the preset error allowable value; if not, re-acquire the disturbance voltage and disturbance current of the target VSC and redetermine the next VSC port current; if it meets the requirement, calculate the VSC input impedance based on the current VSC port current and the corresponding disturbance voltage.

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