Method for modeling output voltage of PWM converter and application thereof

Abstract

The application discloses a kind of PWM converter's output voltage modeling method and application, belong to new energy grid-connected converter technical field.The application linearly decomposes the voltage output by PWM converter into the sum of modulation component and forced component, and modulation component and forced component are respectively represented by the amplitude and frequency of corresponding rotating vector, can change in real time with the change of control quantity output by alternating current control link, when facing the amplitude-frequency time-varying non-periodic modulation signal under system dynamics, still can effectively fit the instantaneous waveform characteristics of PWM converter output voltage.Effectively fit the output voltage formed by modulation signal through PWM link under system steady state and dynamics at the same time, compared with the existing modeling method based on multidimensional discrete harmonic, can greatly reduce the modeling dimension of PWM converter output voltage.

Description

Technical Field

[0001] This invention belongs to the field of new energy grid-connected converter technology, and more specifically, relates to a method for modeling the output voltage of a PWM converter and its application. Background Technology

[0002] With the construction and development of new power systems, an increasing number of new energy power generation plants are being connected to the AC power grid via power electronic converters. During the dynamic interaction between the grid-connected converter and the AC power grid, the voltage, current, and power of the AC power grid frequently exhibit high-frequency oscillations, seriously threatening the power quality and safe and stable operation of the system, becoming a major challenge for the large-scale grid connection of new energy power generation. In AC power systems containing a high proportion of grid-connected converters, filters, transformers, AC transmission cables, etc., constitute a passive AC power grid, while the grid-connected converter constitutes the voltage source. The grid-connected converter includes an AC current control stage and a PWM stage, also known as a PWM converter. The AC current control stage generates a modulation signal, and the PWM stage, based on the generated modulation signal and its own carrier modulation method, enables the grid-connected converter to operate in a high-frequency on / off mode, forming a voltage with complex high-frequency characteristics. During the dynamic interaction between the grid-connected converter and the AC power grid, under the excitation of the output voltage of the grid-connected converter with complex high-frequency characteristics, the current, voltage, and even power generated at various nodes of the AC power grid will also exhibit high-frequency characteristics. Therefore, the high-frequency oscillation characteristics of AC grid voltage, current, and power under system dynamics are closely related to the dynamic characteristics of the grid-connected converter output voltage. To analyze the dynamic stability of AC power systems and explore the mechanisms of high-frequency oscillation generation and evolution, it is necessary to model the voltage generated by the grid-connected converter under system dynamics based on the modulation signal and PWM stage.

[0003] Current modeling methods for PWM converter output voltage are based on discrete harmonic decomposition (DHD), primarily including single Fourier series, double Fourier series, one-dimensional spectrum analysis, and multiple Fourier series based on multivariate periodic function decomposition. However, these DHD-based modeling methods are only suitable for periodic modulation signals under steady-state conditions or aperiodic modulation signals that can be decomposed into a superposition of discrete periodic components. Under dynamic conditions, the amplitude and frequency of the modulation signal generated by the AC current control loop of the grid-connected converter fluctuate relative to their respective steady-state operating points, causing the modulation signal waveform to change from a sinusoidal signal to a time-varying amplitude-frequency aperiodic signal, making it impossible to use DHD-based modeling methods. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a method and application for modeling the output voltage of a PWM converter, which solves the technical problem that the prior art cannot effectively fit the instantaneous waveform characteristics of the output voltage of the PWM converter when facing the amplitude-frequency time-varying aperiodic modulation signal under dynamic system conditions.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for modeling the output voltage of a PWM converter, comprising: The output of the PWM converter x voltage on phase Linear decomposition into ;in, x It can be a, b, or c; t Indicates time; for x The modulation component on the phase is used to represent the output of the corresponding AC current control loop. x The modulation signal on the phase; for x The forced component on the phase is used to represent The additional signal generated after carrier modulation by the corresponding PWM stage; modulated components Through the magnitude of the corresponding rotation vector and frequency To represent, the forced components will be... Through the magnitude of the corresponding rotation vector and frequency This is expressed in terms of the output voltage of the PWM converter, thus yielding the expression for the output voltage. Among them, modulation components and forced components The expression is as follows:

[0006]

[0007] in, For modulation components The initial phase of the corresponding rotation vector; Forcing Components The initial phase of the corresponding rotation vector; when x When it is a, the coefficient =0; when x When the coefficient is b, -1; when x When it is c, the coefficient =1; amplitude and frequency The amplitude is determined based on the d-axis and q-axis voltage components output by the dq controller in the AC current control loop corresponding to the PWM converter and the reference frequency used for the abc-dq coordinate transformation; and frequency Based on modulation components The carrier signal used in the PWM stage corresponding to the PWM converter is determined.

[0008] More preferably, amplitude and frequency They are respectively:

[0009] in, and These correspond to the d-axis and q-axis voltage components output by the dq controller in the AC current control loop of the PWM converter, respectively. This is the reference frequency used for the abc-dq coordinate transformation in the AC current control loop corresponding to the PWM converter. It represents the derivative of the arctangent function.

[0010] More preferably, amplitude and frequency They are respectively:

[0011] in, and Forcing Components The corresponding rotation vector is Two orthogonal components in a coordinate system; It represents the derivative of the arctangent function.

[0012] More preferably, when the carrier signal used in the PWM stage corresponding to the above-mentioned PWM converter is a rising sawtooth carrier, the forced component... The corresponding rotation vector is Two orthogonal components in the coordinate system , They are respectively:

[0013]

[0014] in, ; The period of the carrier signal.

[0015] More preferably, when the carrier signal used in the PWM stage corresponding to the above-mentioned PWM converter is a falling sawtooth carrier, the forced component... The corresponding rotation vector is Two orthogonal components in the coordinate system , They are respectively:

[0016]

[0017] in, ; The period of the carrier signal.

[0018] More preferably, when the carrier signal used in the PWM stage corresponding to the above-mentioned PWM converter is a symmetrical triangular carrier, the forced component... The corresponding rotation vector is Two orthogonal components in the coordinate system , They are respectively:

[0019]

[0020] in, ; The period of the carrier signal.

[0021] Secondly, the present invention provides a stability analysis method for an AC power system; wherein the AC power system includes an AC power grid and multiple PWM converters; The stability analysis methods mentioned above include: For each PWM converter, substitute the d and q axis voltage components output by the dq controller in the AC current control loop of the PWM converter at the current moment and the reference frequency used for the abc-dq coordinate transformation into the voltage expression to obtain the voltage output of the PWM converter at the current moment. Based on the AC power grid model and the voltage output of each PWM converter at the current moment, the current physical quantity of the target node in the AC power grid is calculated, and then the stability of the AC power system at the current moment is analyzed. The voltage expression is constructed using the output voltage modeling method of the PWM converter provided in the first aspect of this invention; the physical quantities mentioned above include: voltage, current, active power and reactive power.

[0022] Thirdly, the present invention provides an AC power system, comprising: an AC power grid, multiple PWM converters, and a controller; The controller is used to execute the stability analysis method provided in the second aspect of the present invention.

[0023] Fourthly, the present invention provides an electronic device, comprising: a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the output voltage modeling method for a PWM converter provided in the first aspect of the present invention or the stability analysis method provided in the second aspect.

[0024] Fifthly, the present invention also provides a computer-readable storage medium comprising a stored computer program, wherein, when the computer program is run by a processor, it controls the device where the storage medium is located to execute the output voltage modeling method for a PWM converter provided in the first aspect of the present invention or the stability analysis method provided in the second aspect of the present invention.

[0025] In a sixth aspect, the invention also provides a computer program product, including a computer program / instruction that, when executed by a processor, implements the output voltage modeling method for the PWM converter provided in the first aspect of the invention or the stability analysis method provided in the second aspect.

[0026] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects: 1. This invention provides a method for modeling the output voltage of a PWM converter. Based on the working mechanism of the PWM stage and the equivalence principle and linear superposition of impulse, the voltage output of the PWM converter is linearly decomposed into the sum of a modulation component and a forced component. The modulation component and the forced component represent the modulation signal output by the AC current control stage and the additional signal formed after the modulation signal is modulated by the carrier of the corresponding PWM stage, respectively. According to the correspondence between the instantaneous value of the alternating signal and the projection of its corresponding rotating vector on the coordinate axis, the modulation component and the forced component are represented by the amplitude and frequency of the corresponding rotating vector, respectively. The amplitude and frequency of the rotating vector corresponding to the modulation component are determined based on the d and q axis voltage components output by the dq controller in the AC current control stage of the PWM converter and the reference frequency used for the abc-dq coordinate transformation. This allows the method to change in real time with the change of the control quantity output by the AC current control stage. When facing a time-varying amplitude-frequency aperiodic modulation signal under dynamic system conditions, the instantaneous waveform characteristics of the PWM converter output voltage can still be effectively fitted.

[0027] 2. When facing a periodic modulation signal in steady state or a non-periodic modulation signal that can be decomposed into a superposition of discrete periodic components, compared with the existing modeling methods that require multi-dimensional discrete harmonics to effectively fit the target voltage, resulting in a high model dimensionality, the output voltage modeling method of the PWM converter provided by this invention can achieve the same fitting accuracy as the existing modeling methods based on multi-dimensional discrete harmonics using only two-dimensional amplitude and frequency, thereby significantly reducing the modeling dimensionality of the PWM converter output voltage. Attached Figure Description

[0028] Figure 1 A typical system block diagram of a three-phase converter for AC grid connection under the action of AC current control and PWM stages, provided in an embodiment of the present invention; Figure 2A schematic diagram illustrating the formation and linear decomposition of the PWM voltage of a grid-connected converter into modulation and forced components under modulation and carrier signals, as provided in an embodiment of the present invention. Figure 3 A schematic diagram illustrating the amplitude and frequency characterization of the output voltage of a PWM converter based on modulation vectors and forcing vectors, provided for embodiments of the present invention; Figure 4 A schematic diagram of the principle of representing modulation components based on modulation vectors provided for embodiments of the present invention; Figure 5 A schematic diagram illustrating the principle of representing forced components based on forced vectors, provided for embodiments of the present invention; Figure 6 The present invention provides a forced component formed by a modulated signal and a method for characterizing it, which is derived from a modulated signal and a rising sawtooth carrier signal. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] To achieve the above objectives, in a first aspect, the present invention provides a method for modeling the output voltage of a PWM converter, comprising: The output of the PWM converter x voltage on phase Linear decomposition into ;in, x It can be a, b, or c; t Indicates time; for x The modulation component on the phase is used to represent the output of the corresponding AC current control loop. x The modulation signal on the phase; for x The forced component on the phase is used to represent The additional signal generated after carrier modulation by the corresponding PWM stage; modulated components Through the magnitude of the corresponding rotation vector and frequency To represent, the forced components will be... Through the magnitude of the corresponding rotation vector and frequency This is expressed in terms of the output voltage of the PWM converter, thus yielding the expression for the output voltage. Among them, modulation components and forced components The expression is as follows:

[0031]

[0032] in, For modulation components The initial phase of the corresponding rotation vector; Forcing Components The initial phase of the corresponding rotation vector; when x When it is a, the coefficient =0; when x When the coefficient is b, -1; when x When it is c, the coefficient =1; amplitude and frequency The amplitude is determined based on the d-axis and q-axis voltage components output by the dq controller in the AC current control loop corresponding to the PWM converter and the reference frequency used for the abc-dq coordinate transformation; and frequency Based on modulation components The carrier signal used in the PWM stage corresponding to the PWM converter is determined.

[0033] In one alternative implementation, the amplitude and frequency They are respectively:

[0034] in, and These correspond to the d-axis and q-axis voltage components output by the dq controller in the AC current control loop of the PWM converter, respectively. This is the reference frequency used for the abc-dq coordinate transformation in the AC current control loop corresponding to the PWM converter. represents the derivative of the arctangent function, and represents the derivative with respect to t.

[0035] In one alternative implementation, the amplitude and frequency They are respectively:

[0036] in, and Forcing Components The corresponding rotation vector is Two orthogonal components in a coordinate system; represents the derivative of the arctangent function, and represents the derivative with respect to t.

[0037] It should be noted that when the type of carrier signal used in the PWM stage of the PWM converter is different, the above... and The expressions are also different.

[0038] In one alternative implementation, when the carrier signal used in the PWM stage corresponding to the aforementioned PWM converter is a rising sawtooth carrier, the forced component... The corresponding rotation vector is Two orthogonal components in the coordinate system , They are respectively:

[0039]

[0040] in, ; The period of the carrier signal.

[0041] In an optional second implementation, when the carrier signal used in the PWM stage corresponding to the above-mentioned PWM converter is a falling sawtooth carrier, the forced component... The corresponding rotation vector is Two orthogonal components in the coordinate system , They are respectively:

[0042]

[0043] in, ; The period of the carrier signal.

[0044] In an optional third embodiment, when the carrier signal used in the PWM stage corresponding to the above-mentioned PWM converter is a symmetrical triangular carrier, the forced component... The corresponding rotation vector is Two orthogonal components in the coordinate system , They are respectively:

[0045]

[0046] in, ; The period of the carrier signal.

[0047] It should be noted that the forced component The corresponding rotation vector is Two orthogonal components in the coordinate system , Based on modulation components The carrier signal used in the PWM stage corresponding to the PWM converter is determined. Different carrier signals have different waveform characteristics, and therefore different expressions.

[0048] When the carrier signal is a rising sawtooth carrier This can be expressed as a representation of the modulating signal. and rising sawtooth carrier signal The composite function is shown in the following equation:

[0049] The above expression is then obtained by expanding it using Fourier series. .

[0050] When the carrier signal is a falling sawtooth carrier This can be expressed as a representation of the modulating signal. and rising sawtooth carrier signal The composite function is shown in the following equation:

[0051] The above expression is then obtained by expanding it using Fourier series. .

[0052] When the carrier signal is a symmetrical triangular carrier This can be expressed as a representation of the modulating signal. and rising sawtooth carrier signal The composite function is shown in the following equation:

[0053] in, and These are respectively symmetrical triangular carriers The equivalent split corresponds to the rising sawtooth carrier and the falling sawtooth carrier.

[0054] The above expression is then obtained by expanding it using Fourier series. .

[0055] In obtaining Then, the result can be obtained through Hilbert transform. Corresponding orthogonal components .

[0056] To further illustrate the output voltage modeling method of the PWM converter provided by the present invention, a specific embodiment is described in detail below: This embodiment provides a method for modeling the output voltage of a PWM converter. Figure 1 The three-phase converter AC grid-connected system shown is a typical application scenario of this embodiment, aiming to achieve effective fitting of the grid-connected converter PWM voltage formed by an arbitrary, differentiable, and unmodulated modulation signal through a PWM stage. The specific implementation principle and method are as follows: 1. Regarding the linear decomposition of the PWM voltage output by a grid-connected converter (i.e., a PWM converter) and its rotational vector magnitude and frequency characterization. like Figure 2 As shown, Figure 1 The PWM converter output in x voltage on phase Formed by AC current control element x Modulation signal on phase Carrier signal after PWM stage Formed after modulation. Based on the working mechanism of the PWM stage and the equivalent principle of impulse, the voltage... With modulated signal Equivalent in the time scale of the modulated signal. Furthermore, based on the linear superposition property of impulses, the voltage... It can be represented as a modulated signal This is a linear superposition of a high-frequency component of the carrier signal's time scale, which is additionally formed due to carrier modulation. Therefore, as... Figure 2 As shown, the voltage Linear decomposition into two components and ,in It directly corresponds to the modulation signal and reflects the regulation effect of the AC current control link. When it is used to characterize voltage, it is called the "modulation component". This component, which does not reflect the regulating effect of the AC current control loop but is forced to form solely due to carrier modulation, is called the "forced component." The corresponding mathematical relationship is shown in the following equation:

[0057] Any alternating signal can be characterized as the projection of its corresponding rotating vector onto the coordinate axes. The instantaneous waveform characteristics of the alternating signal are determined by the motion state of its corresponding rotating vector, which in turn is determined by the changes in its amplitude (i.e., vector magnitude) and frequency (i.e., vector rotation angular velocity). Therefore, any alternating signal can be characterized by the amplitude and frequency of its corresponding rotating vector. Figure 3 As shown, based on the correspondence between the instantaneous value of the alternating signal and the projection of its corresponding rotation vector onto the coordinate axes, the modulation component... and forced components As two alternating signals, they can be represented by the amplitude and frequency of their respective rotating vectors, i.e., the modulation vectors. amplitude and frequency and forced vector amplitude and frequency To characterize.

[0058] Modulation component From the modulation vector amplitude and frequency The decision is as follows:

[0059] in, For modulation components The initial phase of the corresponding rotation vector; when x When it is a, the coefficient =0; when x When the coefficient is b, -1; when x When it is c, the coefficient The value is 1.

[0060] Similarly, forced components By forced vector amplitude and frequency The decision is as follows:

[0061] in, Forcing Components The initial phase of the corresponding rotation vector.

[0062] Due to voltage It is a modulation component and forced components The linear summation can therefore be obtained by modulating the vector. amplitude and frequency and forced vector amplitude and frequency Combination to achieve voltage The representation of voltage. In this way, in order to achieve voltage... For an effective fit, further acquisition of the modulation vector is needed. amplitude and frequency and forced vector amplitude and frequency .

[0063] 2. In terms of modulation vector amplitude and frequency modeling Modulation component This directly corresponds to the modulation signal generated by the AC current control element. For example... Figure 1 and Figure 4 As shown, the output of the dq controller in the AC current control loop is and It is the modulation vector The projections onto the dq coordinate axes respectively, and the reference frequency used in the abc-dq coordinate transformation. It is the rotational angular velocity of the dq coordinate axis. Therefore, the modulation vector amplitude and frequency Output from the dq controller and and the reference frequency used for the abc-dq coordinate transformation The decision is as follows:

[0064] 3. In terms of forced vector magnitude and frequency modeling Forced component The modulation signal generated by the AC current control stage is additionally generated after carrier modulation by the PWM stage, thus forcing the vector. amplitude and frequency Modulation signal generated by alternating current control element The carrier signal used in the PWM stage Decide.

[0065] like Figure 5 As shown, the forced vector exist coordinate axes in a coordinate system The projection on is denoted as Taking a rising sawtooth carrier signal as an example, such as... Figure 6 As shown, based on the characteristics of carrier modulation, the modulating signal... and rising sawtooth carrier signal The resulting forced vector On the coordinate axes Projection on This can be expressed as a representation of the modulating signal. and rising sawtooth carrier signal The composite function is shown in the following equation:

[0066] in, ; The period of the carrier signal.

[0067] Rising sawtooth carrier signal As a periodic signal, it can be expanded using Fourier series. By analyzing the equation... The outer part of the composite function By performing a Fourier series expansion, we can obtain a form with amplitude and frequency modulation. The analytical expression is shown below:

[0068] To determine the forcing vector amplitude and frequency We also need to obtain the forcing vector. In relation to the coordinate axes mutually orthogonal coordinate axes The projection on, i.e., the component Corresponding orthogonal components .

[0069] The Hilbert transform is an effective method for establishing orthogonality between signals. The inner product of two signals before and after the Hilbert transform remains zero at any given time, meaning they remain orthogonal to each other at any time. This can be demonstrated by the equation... The components shown By performing a Hilbert transform, the components can be obtained. Corresponding orthogonal components As shown in the following formula:

[0070] like Figure 5 As shown, according to the forced vector With shaft and Axis orthogonal projection and The triangular relationship can be used to obtain the forced vector. amplitude and frequency As shown in the following formula:

[0071] In summary, the PWM converter output voltage modeling method provided in this embodiment can effectively fit the grid-connected converter PWM voltage formed by the modulation signal (i.e., any differentiable and non-overmodulated modulation signal) through the PWM stage in both steady-state and dynamic states using only two-dimensional amplitude and frequency. Therefore, compared with the existing modeling method based on discrete harmonic decomposition, it has more general and extensive application scenarios, and at the same time, it significantly reduces the modeling dimension of the PWM converter output voltage.

[0072] Secondly, the present invention provides a stability analysis method for an AC power system; wherein the AC power system includes an AC power grid and multiple PWM converters; The stability analysis methods mentioned above include: For each PWM converter, substitute the d and q axis voltage components output by the dq controller in the AC current control loop of the PWM converter at the current moment and the reference frequency used for the abc-dq coordinate transformation into the voltage expression to obtain the voltage output of the PWM converter at the current moment. Based on the AC power grid model and the voltage output of each PWM converter at the current moment, the current physical quantity of the target node in the AC power grid is calculated, and then the stability of the AC power system at the current moment is analyzed. The voltage expression is constructed using the output voltage modeling method of the PWM converter provided in the first aspect of this invention; the physical quantities mentioned above include: voltage, current, active power and reactive power.

[0073] It should be noted that the above AC power grid model is a combination of filter model, transformer model, and transmission line model according to their connection relationship.

[0074] When analyzing the stability of an AC power system at a given moment, the stability can be analyzed based on the voltage, current, active power, and reactive power of the target nodes in the AC power grid, using stability analysis criteria. These criteria can include the Nyquist criterion, the Lyapunov criterion, etc., and are not limited here.

[0075] After conducting a stability analysis on the AC power system, the results of the stability analysis can be used to guide the AC current control mechanism to better control the AC power system.

[0076] The related technical solutions are the same as the output voltage modeling method of the PWM converter provided in the first aspect of this invention, and are not limited here.

[0077] Thirdly, the present invention provides an AC power system, comprising: an AC power grid, multiple PWM converters, and a controller; The controller is used to execute the stability analysis method provided in the second aspect of the present invention.

[0078] The related technical solutions are the same as the stability analysis method provided in the second aspect of this invention, and are not limited here.

[0079] Fourthly, the present invention provides an electronic device, comprising: a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the output voltage modeling method for a PWM converter provided in the first aspect of the present invention or the stability analysis method provided in the second aspect.

[0080] The related technical solutions are the same as the output voltage modeling method of the PWM converter provided in the first aspect of the present invention and the stability analysis method provided in the second aspect of the present invention, and are not limited here.

[0081] Fifthly, the present invention also provides a computer-readable storage medium comprising a stored computer program, wherein, when the computer program is run by a processor, it controls the device where the storage medium is located to execute the output voltage modeling method for a PWM converter provided in the first aspect of the present invention or the stability analysis method provided in the second aspect of the present invention.

[0082] The related technical solutions are the same as the output voltage modeling method of the PWM converter provided in the first aspect of the present invention and the stability analysis method provided in the second aspect of the present invention, and are not limited here.

[0083] In a sixth aspect, the invention also provides a computer program product, including a computer program / instruction that, when executed by a processor, implements the output voltage modeling method for the PWM converter provided in the first aspect of the invention or the stability analysis method provided in the second aspect.

[0084] The related technical solutions are the same as the output voltage modeling method of the PWM converter provided in the first aspect of the present invention and the stability analysis method provided in the second aspect of the present invention, and are not limited here.

[0085] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for modeling the output voltage of a PWM converter, characterized in that, include: The output of the PWM converter x voltage on phase Linear decomposition into ; x It can be a, b, or c; t Indicates time; for x The modulation component on the phase is used to represent the output of the corresponding AC current control loop. x The modulation signal on the phase; for x The forced component on the phase is used to represent The additional signal generated after carrier modulation by the corresponding PWM stage; modulated components Through the magnitude of the corresponding rotation vector and frequency To represent, the forced components will be... Through the magnitude of the corresponding rotation vector and frequency This is expressed in terms of the output voltage of the PWM converter, thus yielding the expression for the output voltage. The modulation component and the forced component The expression is as follows: in, Modulation component The initial phase of the corresponding rotation vector; Forcing Components The initial phase of the corresponding rotation vector; when x When it is a, the coefficient =0; when x When the coefficient is b, -1; when x When it is c, the coefficient The amplitude is 1; and the frequency The amplitude is determined based on the d-axis and q-axis voltage components output by the dq controller in the AC current control loop corresponding to the PWM converter and the reference frequency used for the abc-dq coordinate transformation; and the frequency Based on modulation components The carrier signal used in the PWM stage corresponding to the PWM converter is determined.

2. The output voltage modeling method for a PWM converter according to claim 1, characterized in that, The amplitude and the frequency They are respectively: in, and These correspond to the d-axis and q-axis voltage components output by the dq controller in the AC current control loop of the PWM converter, respectively. This is the reference frequency used for the abc-dq coordinate transformation in the AC current control loop corresponding to the PWM converter. It represents the derivative of the arctangent function.

3. The output voltage modeling method for a PWM converter according to claim 1, characterized in that, The amplitude and the frequency They are respectively: in, and Forcing Components The corresponding rotation vector is Two orthogonal components in a coordinate system; It represents the derivative of the arctangent function.

4. The output voltage modeling method for a PWM converter according to claim 3, characterized in that, When the carrier signal is a rising sawtooth carrier, the forced component The corresponding rotation vector is Two orthogonal components in the coordinate system , They are respectively: in, ; The period of the carrier signal is denoted as .

5. The output voltage modeling method for a PWM converter according to claim 3, characterized in that, When the carrier signal is a falling sawtooth carrier, the forced component The corresponding rotation vector is Two orthogonal components in the coordinate system , They are respectively: in, ; The period of the carrier signal is denoted as .

6. The output voltage modeling method for a PWM converter according to claim 3, characterized in that, When the carrier signal is a symmetrical triangular carrier, the forced component The corresponding rotation vector is Two orthogonal components in the coordinate system , They are respectively: in, ; The period of the carrier signal is denoted as .

7. A stability analysis method for an AC power system, characterized in that, The AC power system includes an AC power grid and multiple PWM converters; The stability analysis method includes: For each PWM converter, substitute the d and q axis voltage components output by the dq controller in the AC current control loop of the PWM converter at the current moment and the reference frequency used for the abc-dq coordinate transformation into the voltage expression to obtain the voltage output of the PWM converter at the current moment. Based on the AC power grid model and the voltage output of each PWM converter at the current moment, the current physical quantity of the target node in the AC power grid is calculated, and then the stability of the AC power system at the current moment is analyzed. The voltage expression is constructed using the output voltage modeling method of the PWM converter as described in any one of claims 1-6; the physical quantities include: voltage, current, active power, and reactive power.

8. An alternating current power system, characterized in that, include: AC power grid, multiple PWM converters and controllers; The controller is used to execute the stability analysis method according to claim 7.

9. An electronic device, characterized in that, include: A memory and a processor, the memory storing a computer program, the processor executing the computer program to perform the method according to any one of claims 1-7.

10. A computer program product, characterized in that, Includes a computer program / instruction that, when executed by a processor, implements the method described in any one of claims 1-7.

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