VSC (Voltage Source Converter) impedance analysis method in superposition oscillation component scene and related device

Abstract

The invention belongs to the field of two-level converter small signal and impedance modeling, and discloses a VSC impedance analysis method in a superposition oscillation component scene and a related device. The method comprises the following steps of: superposing an alternating-current voltage oscillation component, and establishing each steady-state quantity frequency domain model; establishing a main circuit steady-state frequency domain model; establishing each small semaphore frequency domain model based on the main circuit steady-state frequency domain model; establishing a main circuit small signal frequency domain model; constructing a PLL controller small signal model, a DC voltage controller small signal model and an AC current controller small signal model; constructing a small signal model of the alternating current modulation signal; and calculating the port impedance of the two-level current converter in the scene of superposition of the oscillation components based on a small signal model of the alternating-current modulation signal. According to the method, the VSC port impedance in the scene of superposition of the oscillation components can be accurately analyzed, and key technical support is provided for oscillation mechanism analysis and stability improvement of new energy access to a weak point network.

Description

Technical Field

[0001] The present invention belongs to the field of small signal and impedance modeling of two-level converters, and in particular relates to a VSC impedance analysis method and related devices in a scenario of superimposed oscillation components. Background Art

[0002] As renewable energy development expands into remote areas such as deserts and Gobi Desert, broadband oscillations caused by the integration of weak grids into renewable energy systems are becoming increasingly prominent. In weak grid environments, the interaction between oscillating currents and grid impedance can cause the amplitude of the oscillating voltage to exceed the oscillating current, further accentuating broadband oscillations characterized by voltage fluctuations. Broadband voltage oscillations encompass multiple stages, including static stability, voltage fluctuations, and continuous high and low voltage ride-through. However, constructing a unified model that comprehensively describes the evolution of broadband voltage oscillations, from linear to nonlinear, and even nonlinear dynamic processes, remains a major challenge.

[0003] On the other hand, the mathematical model of a two-level converter incorporates multiple nonlinear elements, such as insulated-gate bipolar transistor (IGBT) switches, pulse-width modulation (PWM), Park transform, and phase-locked loop (PLL). Furthermore, the dynamic characteristics of the DC bus, as a non-ideal voltage source, significantly impact the multi-frequency coupling characteristics of broadband oscillations and the accuracy of the Nyquist stability criterion. In particular, under oscillation scenarios, the steady-state operating point and small-signal frequency-domain characteristics of the two-level converter undergo fundamental changes due to the superimposed oscillatory components, making the analysis of its impedance model quite challenging.

[0004] Existing research has mostly focused on oscillations generated during steady-state operation. Modeling and analysis of operating point variations during oscillations is rare, making it difficult to describe the characteristic changes from oscillation onset to development, and unable to accurately determine the evolution and dynamic trends of oscillations. Existing methods have the following limitations: (1) Existing impedance analysis methods do not consider the complexity of multi-frequency interactions. In an oscillation scenario, the interaction and coupling between the fundamental frequency component and the oscillation component will derive multiple frequency components, which together constitute the steady-state operating point of the two-level converter and further affect the frequency distribution of small signal quantities, which will change the impedance characteristics of the system and affect the system stability. However, most existing methods ignore the interaction between multiple frequencies, which may lead to inaccurate impedance analysis models and analysis results.

[0005] (2) The analytical modeling of the VSC impedance in the scenario with only the fundamental frequency component cannot meet the impedance modeling requirements in the oscillating scenario. The corresponding impedance analytical model is constructed by applying a small signal perturbation when the system is operating stably. However, in the oscillating scenario, the presence of the oscillating component will cause the system operating point to change. The analytical modeling of the VSC impedance in the scenario with only the fundamental frequency component is difficult to characterize the impedance characteristics in the oscillating scenario.

[0006] In order to solve the above technical difficulties, it is urgent to propose a new method to analyze the VSC port impedance in the scenario of superimposed oscillation components. Summary of the Invention

[0007] To achieve the above objectives, the present invention provides a VSC impedance analysis method and related devices in a scenario with superimposed oscillation components, so as to solve the technical problem that the existing technology cannot accurately analyze the VSC port impedance in a scenario with superimposed oscillation components; and provide key technical support for the oscillation mechanism analysis and stability improvement of new energy access weak network.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a VSC impedance analysis method in a scenario with superimposed oscillation components, comprising: superimposing an AC voltage oscillation component to establish frequency domain models of various steady-state quantities; establishing a steady-state frequency domain model of a main circuit based on the AC / DC side conversion relationship and the frequency domain models of various steady-state quantities; injecting a small-signal voltage disturbance at the output end of a two-level converter to establish frequency domain models of various small-signal quantities; establishing a small-signal frequency domain model of a main circuit based on the AC / DC side conversion relationship and the frequency domain models of various small-signal quantities; constructing a PLL controller small-signal model, a DC voltage controller small-signal model, and an AC current controller small-signal model based on the control structure of each controller; constructing an AC modulation signal small-signal model based on the PLL controller small-signal model, the DC voltage controller small-signal model, and the AC current controller small-signal model; and calculating the port impedance of the two-level converter in the scenario with superimposed oscillation components based on the AC modulation signal small-signal model and the main circuit small-signal frequency domain model.

[0009] In a second aspect, the present application provides a VSC impedance analysis device under an oscillation component superimposition scenario, comprising: a first construction module, configured to superimpose an alternating voltage oscillation component, and establish a frequency domain model of each steady-state quantity; a second construction module, configured to establish a main circuit steady-state frequency domain model according to a conversion relationship between AC and DC sides and the frequency domain model of each steady-state quantity; a third construction module, configured to inject a small signal voltage disturbance at an output end of the two-level converter, and establish a frequency domain model of each small signal quantity; a fourth construction module, configured to establish a main circuit small signal frequency domain model according to the conversion relationship between AC and DC sides and the frequency domain model of each small signal quantity; a fifth construction module, configured to construct a PLL controller small signal model, a DC voltage controller small signal model and an AC current controller small signal model based on a control structure of each controller; a sixth construction module, configured to construct an AC modulation signal small signal model based on the PLL controller small signal model, the DC voltage controller small signal model and the AC current controller small signal model; and an impedance analysis module, configured to calculate the two-level converter port impedance under the oscillation component superimposition scenario based on the AC modulation signal small signal model and the main circuit small signal frequency domain model.

[0010] In a third aspect, the present 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 VSC impedance analysis method under the oscillation component superimposition scenario.

[0011] In a fourth aspect, the present 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 VSC impedance analysis method under the oscillation component superimposition scenario.

[0012] Compared with the prior art, the present application has the following unexpected technical effects: In view of the VSC port impedance analysis problem under the oscillation component superimposition scenario, the present application proposes a VSC impedance analysis method under the oscillation component superimposition scenario based on the VSC steady-state working point and small signal frequency domain characteristics under the oscillation scenario, and in detail, constructs a small signal frequency domain model of each control loop of the VSC, and an port impedance analysis model under the oscillation scenario. The method proposed in the present application can accurately analyze the VSC port impedance under the oscillation component superimposition scenario, and provides key technical support for the oscillation mechanism analysis and stability improvement of new energy access to weak grids. BRIEF DESCRIPTION OF DRAWINGS

[0013] The accompanying drawings, which form a part of the present application, are used to provide a further understanding of the present application, and the illustrative embodiments of the present application and their description serve the purpose of explaining the present application. The present application is not limited by the improper interpretation of the accompanying drawings. In the drawings: Figure 1 It is a schematic diagram of the two-level converter topology structure; Figure 2 This is the phase-locked loop control block diagram; Figure 3 It is the block diagram of DC voltage control; Figure 4 This is the block diagram of AC current control; Figure 5 Schematic diagram of a flow chart of a VSC impedance analysis method in a scenario with superimposed oscillation components according to an embodiment of the present invention; Figure 6 Schematic diagram of the small signal waveform and FFT result of the q-axis component of the AC voltage; Figure 7 Schematic diagram of the small signal waveform and FFT result of the current d-axis reference command; Figure 8 Schematic diagram of the small signal waveform and FFT result of the AC modulated signal; Figure 9 Schematic diagram of the analysis and scanning results of positive sequence impedance and positive sequence coupling impedance; Figure 10 Schematic diagram of the analysis and scanning results of negative sequence impedance and negative sequence coupling impedance; Figure 11 Schematic diagram of the flow of another VSC impedance analysis method in a scenario with superimposed oscillation components according to an embodiment of the present invention; Figure 12 This is a schematic structural diagram of a VSC impedance analysis device in a scenario where an oscillation component is superimposed according to an embodiment of the present invention; Figure 13 The figure is a schematic structural diagram of an electronic device of the present invention. DETAILED DESCRIPTION

[0014] 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 of the embodiments of the present invention can be combined with each other.

[0015] The following detailed description is an exemplary description and 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 to which the present invention belongs. 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.

[0016] This invention proposes a VSC impedance analysis method for scenarios with superimposed oscillatory components. The two-level converter topology employing this method includes a DC bus capacitor 1, an IGBT inverter 2, and a smoothing reactor 3. The DC bus capacitor 1's terminals are connected to the DC side of the IGBT inverter 2, which consists of a six-pulse IGBT inverter valve group. The IGBT inverter's three-phase output current is delivered by the smoothing reactor 3. 、 、 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 a, b, and c phase AC modulation voltages respectively.

[0017] See also Figures 1 to 5 As shown, the embodiment of the present invention proposes a VSC impedance analysis method in a scenario with a superimposed oscillation component, which specifically includes the following steps: Step 1: superimpose the AC voltage oscillation component and establish the frequency domain model of each steady-state quantity; superimpose 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 ( h 、 k They are and The coefficient of , ), where g is the highest number of iterations considered. For ease of presentation, the steady-state frequency sequence is written in a two-dimensional matrix form. In actual calculation, the columns are connected end to end to form a column vector. The steady-state frequency sequence matrix of the three-phase AC component can be expressed as: (1) The steady-state frequency sequence matrix of the DC component can be expressed as: (2) Step 1.1, With frequency Multiplying the steady-state components of The phase sequence of the steady-state components changes, because the frequency is The oscillation component and frequency are The oscillation components of are all positive sequence, then for the frequency The steady-state component of the three phases is: (3) Where n is an integer; The modulo function describing its phase sequence relationship is: (4) According to the phase sequence relationship between the three phases, the steady-state AC voltage of phase a is , a-phase AC current steady-state quantity , steady-state quantity of phase a AC modulation signal , we can get the steady-state quantities of the AC voltage, AC current and AC modulation signal of phases b and c: (5) in, is the steady-state value of phase c AC voltage, is the steady-state value of phase b AC voltage, is the steady-state phase sequence coefficient matrix, for The conjugate of is the steady-state value of phase b AC current, is the steady-state quantity of the c-phase AC modulation signal; (6) Where j is the imaginary unit; For each steady-state matrix, the frequency satisfies The steady-state component is positive sequence, and the frequency combination satisfies The steady-state component is zero sequence, and the frequency combination satisfies The steady-state component of is negative sequence; According to the phase sequence relationship between the three phases, the frequency domain steady-state operating points of the positive and cosine functions of phases b and c are: (7) Where, is a sine function The steady-state quantity, is the cosine function The steady-state quantity, 、 Sine functions 、 The steady-state quantity, 、 The cosine function 、 The steady-state quantity of By applying Park transformation to the three-phase AC voltage, the steady-state quantities of the d-axis and q-axis components of the AC voltage are obtained as follows: (8) Where, 、 are the steady-state quantities of the d-axis and q-axis components of the AC voltage respectively; Step 1.2, based on the frequency domain convolution theorem, the Toplitz matrix expansion method is established: the product in the time domain corresponds to the convolution in the frequency domain, with For example, first To expand, the method is as follows: (1) First, Reverse each column, then reverse each row, connect the elements of the new matrix end to end in the order of columns, and then transpose them to form a row vector, which is the middle row of the expanded matrix. (2) All columns are shifted left first elements, and the remaining elements The first coefficient is incremented, then all rows are shifted up elements, and the remaining elements The first coefficient increases, and the elements of the new matrix after filling are connected in the order of columns to form a row vector, which is the first OK; (3) Shift all columns left elements, and the remaining elements The first coefficient is incremented, then all rows are shifted down elements, and the remaining elements The first coefficient decreases, and the elements of the new matrix after filling are connected in the order of columns to form a row vector, which is the first OK; (4) Shift all columns right elements, and the remaining elements The first coefficient is decreased, and then all rows are moved up elements, and the remaining elements The first coefficient increases, and the elements of the new matrix after filling are connected in the order of columns to form a row vector, which is the first OK; (5) Shift all columns right elements, and the remaining elements The first coefficient is decreased, and then all rows are moved down elements, and the remaining elements The first coefficient decreases, and the elements of the new matrix after filling are connected in the order of columns to form a row vector, which is the first OK; After using the above-mentioned Toplitz matrix expansion method, After connecting them end to end in the order of columns to form a column vector, The frequency domain convolution operation in can be replaced by scalar product. The frequency domain convolution operation result is finally obtained through the scalar product and summation operation of the matrix and column vector. Step 2: According to the AC / DC side conversion relationship, the steady-state frequency domain model of the main circuit is established; according to the AC / DC voltage and current relationship of the two-level converter, the steady-state quantity of the three-phase modulation voltage is calculated. , DC voltage steady-state quantity , steady-state quantity of three-phase AC modulation signal The relationship between them is: (9) The frequency domain steady-state model of the two-level converter AC circuit is: (10) Where, is the AC filter inductor impedance under steady-state frequency sequence, and its expression is: (11) Where, L f is the AC filter inductor; The DC bus frequency domain steady-state model expression is: (12) Where, is the steady-state DC current, is the steady-state quantity of DC capacitance, and its expressions are: (13) (14) Where, is the DC bus capacitance; Step 3: Inject a small signal voltage disturbance at the grid connection point of the two-level converter with a frequency of , establish the frequency domain model of each small signal quantity; in order to describe the frequency domain characteristics of the small signal of each link of the two-level converter, the small signal frequency sequence matrix expression of the three-phase AC component is: (15) The matrix expression of the small signal frequency sequence of the DC component is: (16) Step 3.1, for the frequency The small signal component of the three phases is: (17) The modulo function describing its phase sequence relationship is: (18) According to the phase sequence relationship between the three phases, the a-phase AC voltage small signal vector , a-phase AC current small signal vector , the small signal vector of the a-phase AC modulation signal , we can get the small signal vectors of the AC voltage, AC current and AC modulation signal of phases b and c, namely: (19) in (20) Where, is the small signal vector phase sequence coefficient matrix; For each small signal matrix, the frequency satisfies The small signal component of is positive sequence, and the frequency combination satisfies The small signal component of is zero sequence, and the frequency combination satisfies The small signal component of is negative sequence.

[0018] Step 4: Based on the AC / DC side conversion relationship, a small-signal frequency-domain model of the main circuit is established. The frequency-domain small-signal model of the modulation voltage of the two-level converter can be expressed as: (twenty one) Where, is the modulation voltage small signal vector, is the PWM gain, is the steady-state vector of the three-phase AC modulation signal, is the DC voltage small signal vector, is the DC voltage steady-state vector, is the small signal vector of the three-phase AC modulation signal; The frequency domain small signal component model of the AC circuit can be expressed as: (twenty two) Where, is the modulation voltage small signal vector, is the AC filter inductor impedance under the small signal frequency sequence, and its expression is: (twenty three) The DC bus frequency domain small signal model can be expressed as: (twenty four) in (25) Where, is the DC bus capacitance admittance under small signal frequency sequence; Substituting Equation (22) into Equation (24), we can obtain the DC voltage small signal vector and the small signal vector of phase a AC voltage , a-phase AC current small signal vector The relationship between them is: (26) in, is the transfer matrix between the DC voltage small signal vector and the AC voltage small signal vector, is the transfer matrix between the DC voltage small signal vector and the AC current small signal vector: (27) Step 5: Construct a small signal model of the PLL controller. The three-phase AC voltage is transformed by Park to obtain the AC voltage d-axis and q-axis components, namely: (28) Superimposed voltage small signal f p After that, the a, b, c phase AC voltage small signal matrix 、 and This will result in a phase-locked angular frequency domain small signal vector Convert Equation (29) to the frequency domain, ignore the second-order and above small signal components, and obtain the d-axis and q-axis components of the AC voltage small signal after Park transformation. 、 They are: (29) In Equation (29), the multiplication of two vectors is performed by convolution operation. For the convenience of presentation, the convolution symbol will be omitted here and below. The two-level converter generates the phase-locked angle through PLL control. , as the synchronous rotation reference angle, the phase-locked loop control structure is as follows Figure 2 As shown in the figure, the three-phase AC voltage is transformed into the d-axis and q-axis voltage components respectively through Park transformation, wherein the q-axis voltage component is adjusted by PI and the integral link to generate the phase-locked angle ; Under the control of PLL, the AC voltage small signal disturbance will introduce a small signal component to the phase-locked angle, and the phase-locked angle small signal vector and the q-axis component of the AC voltage small signal The transfer relationship between them is: (30) Substituting Equation (29) into Equation (30) yields the phase-locked angle small signal vector and the small signal vector of phase a AC voltage The transfer relationship between them is: (31) in: (32) Where, is the identity matrix; Step 6: Construct a small signal model of the DC voltage controller; the DC voltage control structure is as follows: Figure 3 As shown by Figure 3 The AC current small signal d-axis reference instruction can be obtained for: (33) in: (34) Step 7: Construct a small signal model of the AC current controller; the AC current control structure is as follows: Figure 4 As shown by Figure 4 The AC current d and q axis small signal vectors can be obtained 、 and the small signal vector of phase a AC voltage and a phase AC current small signal The transitive relationship is: (35) in: (36) (37) (38) (39) Step 8: Construct a small signal model of AC modulation signal; Figure 4 The small signal d-axis and q-axis components of the AC modulated signal are obtained as follows: (40) in: is the AC current loop transfer function; (41) Substituting equations (36) and (33) into (40), we can obtain the small signal d and q axis vectors of the AC modulated signal 、 The expression is: (42) in: is the transfer matrix between the small signal d-axis vector of the AC modulated signal and the small signal vector of the AC voltage, is the transfer matrix between the small signal d-axis vector of the AC modulated signal and the small signal vector of the AC current, is the transfer matrix between the small signal d-axis vector of the AC modulation signal and the small signal vector of the DC voltage, is the transfer matrix between the small signal q-axis vector of the AC modulated signal and the small signal vector of the AC voltage, is the transfer matrix between the small signal q-axis vector of the AC modulated signal and the small signal vector of the AC current; (43) (44) (45) (46) (47) The d-axis and q-axis components of the AC modulation signal are transformed by inverse Park transform to obtain a three-phase modulation signal. The small signal vector expression of the a-phase AC modulation signal is: (48) in: (49) (50) (51) Step 9: Calculate the port impedance of the two-level converter in the scenario of superimposed oscillation components; Taking the AC current flowing toward the grid as the reference direction, the AC port admittance of the two-level converter is expressed as: (52) Taking phase a as an example, the small signal vector expression of the modulation voltage of phase a is: (53) in: (54) (55) Substituting equation (53) into equation (22), the AC port impedance of the two-level converter can be obtained as: (56) The process of applying the VSC impedance analysis method in the scenario of superimposed oscillation components is as follows: Figure 5 shown.

[0019] To address the difficulty in analyzing VSC impedance in scenarios with superimposed oscillation components, the present invention obtains the VSC steady-state operating point and small-signal frequency components in the oscillation scenario through frequency conversion relationships, accurately analyzes the multi-harmonic interaction coupling characteristics between the oscillation component and the fundamental frequency component, and finely characterizes the steady-state and small-signal frequency sequences of the two-level converter in the oscillation scenario, effectively solving the problem of the difficulty in accurately characterizing the VSC steady-state operating point and small-signal frequency components in the oscillation scenario.

[0020] The present invention proposes a VSC impedance analysis method in a scenario with superimposed oscillating components. The steady-state component frequency sequence and small-signal frequency sequence introduced by the oscillating components are used as the VSC operating trajectory. This method accurately reflects the multi-frequency interaction characteristics of the VSC main circuit and each controller, takes into account the influence of the superimposed oscillating components, and effectively solves the difficult problem of accurately constructing an impedance analysis model caused by the interaction between the oscillating components and the fundamental frequency components.

[0021] The method described in the present invention can accurately analyze the VSC impedance model in an oscillation scenario, providing key technical support for stability analysis and oscillation suppression of two-level converters in a scenario with superimposed oscillation components.

[0022] In this specific application example, the VSC impedance analytical model is verified in a scenario with superimposed oscillation components. The main circuit and control parameters of the two-level converter are shown in Table 1.

[0023] Table 1 Main circuit and control parameters of two-level converter

[0024] According to steps 1 to 8, the analysis results of the q-axis component of the AC voltage of the two-level converter are established, such as Figure 6 As shown, when the oscillation frequency When the frequency is 69Hz, after a small signal disturbance with a frequency of 80Hz is superimposed on the AC voltage, the AC voltage undergoes Park transformation, and the q-axis components of the AC voltage are generated as follows: 、 、 、 and The small signal response of the two-level converter current d-axis reference command component analysis results are established, such as Figure 7 As shown in the figure, when the 80Hz small signal voltage disturbance is superimposed on the AC voltage, after the DC voltage control, the AC current d-axis reference instruction small signal is generated respectively 、 、 、 and The small signal response of the two-level converter AC modulation signal analysis results are established, such as Figure 8 As shown, the AC modulated signal will produce 、 、 、 、 and It can be seen that the small signal waveforms and FFT results of the AC voltage q-axis component, current d-axis reference command component, and AC modulation signal are completely consistent with the results of their small signal frequency domain model.

[0025] According to step 9, the analysis and scanning results of the positive sequence impedance and positive sequence coupling impedance, and the analysis and scanning results of the negative sequence impedance and negative sequence coupling impedance of the two-level converter under the superimposed oscillation component scenario are established, as shown in the following example: Figure 9 、 Figure 10 The impedance analysis results of positive sequence impedance and negative sequence impedance are shown as follows: Figure 9 、 Figure 10 The impedance analysis results of the positive sequence coupling impedance and the negative sequence coupling impedance are shown in the solid line. Figure 9 、 Figure 10 On this basis, a MATLAB / SIMULINK two-level converter simulation model is built, and the two-level converter port impedance simulation results are obtained by impedance sweeping method, as shown in the figure. Figure 9 、 Figure 10 As shown in the figure, the analytical results of the positive-sequence impedance and positive-sequence coupling impedance, as well as the negative-sequence impedance and negative-sequence coupling impedance of the two-level converter are consistent with the simulation results, verifying the accuracy of the VSC impedance analysis method described in this patent in the scenario of superimposed oscillation components.

[0026] See also Figure 11 As shown, an embodiment of the present invention provides a VSC impedance analysis method in a scenario where an oscillation component is superimposed, including: S100, superimposing AC voltage oscillation components to establish frequency domain models of various steady-state quantities; S200, establishing a main circuit steady-state frequency domain model based on the AC / DC side conversion relationship and the frequency domain models of various steady-state quantities; S300, injecting a small signal voltage disturbance into the output end of the two-level converter, and establishing a frequency domain model of each small signal quantity based on the steady-state frequency domain model of the main circuit; S400, establishing a main circuit small signal frequency domain model based on the AC / DC side conversion relationship and the frequency domain models of various small signal quantities; S500, constructing a PLL controller small signal model, a DC voltage controller small signal model, and an AC current controller small signal model based on a main circuit small signal frequency domain model; S600: Construct an AC modulation signal small signal model based on a PLL controller small signal model, a DC voltage controller small signal model, and an AC current controller small signal model; S700: Calculate the port impedance of a two-level converter in a scenario where an oscillating component is superimposed based on a small signal model of an AC modulated signal.

[0027] In a specific embodiment, the step of superimposing the AC voltage oscillation component and establishing the frequency domain model of each steady-state quantity specifically includes: superimposing a frequency of The AC voltage oscillation component, the fundamental frequency is ; Two-level converter contains fundamental frequency and oscillation frequency The steady-state component also contains the linear combination frequency The steady-state component of , ; h 、 k They are and The coefficient of , g is the highest number of iterations considered; the steady-state frequency sequence matrix of the three-phase AC component is obtained: (1) The steady-state frequency sequence matrix of the DC component: (2) With frequency Multiplying the steady-state components of The phase sequence of the steady-state components changes, because the frequency is The oscillation component and frequency are The oscillation components of are all positive sequence, then for the frequency The steady-state component of the three phases is: (3) The modulo function describing its phase sequence relationship is: (4) According to the phase sequence relationship between the three phases, the steady-state AC voltage of phase a is , a-phase AC current steady-state quantity , steady-state quantity of phase a AC modulation signal , we can get the steady-state quantities of the AC voltage, AC current and AC modulation signal of phases b and c: (5) in, is the steady-state value of phase c AC voltage, is the steady-state value of phase b AC voltage, is the steady-state phase sequence coefficient matrix, for The conjugate of is the steady-state value of phase b AC current, is the steady-state quantity of the c-phase AC modulation signal; (6) Where j is the imaginary unit; For each steady-state matrix, the frequency satisfies The steady-state component is positive sequence, and the frequency combination satisfies The steady-state component is zero sequence, and the frequency combination satisfies The steady-state component of is negative sequence; According to the phase sequence relationship between the three phases, the frequency domain steady-state operating points of the positive and cosine functions of phases b and c are: (7) Where, is a sine function The steady-state quantity, is the cosine function The steady-state quantity, 、 The sine functions 、 The steady-state quantity, 、 The cosine function 、 The steady-state quantity of By applying Park transformation to the three-phase AC voltage, the steady-state quantities of the d-axis and q-axis components of the AC voltage are obtained as follows: (8) Where, 、 are the steady-state quantities of the d-axis and q-axis components of the AC voltage respectively; is the steady-state value of phase a AC voltage, is the steady-state value of phase b AC voltage, is the steady-state value of phase c AC voltage; 、 It is calculated based on the Toplitz matrix expansion method established according to the frequency domain convolution theorem in step 1.2 above.

[0028] In a specific embodiment, the step of establishing the main circuit steady-state frequency domain model according to the AC / DC side conversion relationship and the frequency domain model of each steady-state quantity specifically includes: calculating the three-phase modulation voltage steady-state quantity according to the AC / DC voltage and current relationship of the two-level converter. , DC voltage steady-state quantity , steady-state quantity of three-phase AC modulation signal The relationship between: (9) Frequency domain steady-state model of the two-level converter AC circuit: (10) Where, is the AC filter inductor impedance under steady-state frequency sequence, and its expression is: (11) Where, L f is the AC filter inductor; is the AC filter inductor impedance under steady-state frequency sequence; The DC bus frequency domain steady-state model expression is: (12) Where, is the steady-state DC current, is the steady-state quantity of DC capacitance, and its expressions are: (13) (14) Where, is the DC bus capacitor.

[0029] In a specific embodiment, in the step of injecting a small signal voltage disturbance at the output end of the two-level converter and establishing each small signal quantity frequency domain model based on the steady-state frequency domain model of the main circuit, each small signal quantity frequency domain model includes: Small signal frequency sequence matrix of three-phase AC components: (15) Small signal frequency sequence matrix of DC component: (16) For the frequency The small signal component of the three phases is: (17) The modulo function describing its phase sequence relationship is: (18) According to the phase sequence relationship between the three phases, the a-phase AC voltage small signal vector , a-phase AC current small signal vector , small signal vector of phase a AC modulation signal , small signal vectors of phase b and c AC voltage, AC current and AC modulation signal: (19) in, is the a-phase AC voltage small signal vector, is the b-phase AC voltage small signal vector, is the c-phase AC voltage small signal vector, is the small signal vector phase sequence coefficient matrix; is the small signal vector of the a-phase AC modulation signal, is the small signal vector of the b-phase AC modulation signal, is the small signal vector of the c-phase AC modulation signal.

[0030] (20) For each small signal matrix, the frequency satisfies The small signal component of is positive sequence, and the frequency combination satisfies The small signal component of is zero sequence, and the frequency combination satisfies The small signal component of is negative sequence. In a specific embodiment, in the step of establishing the main circuit small signal frequency domain model based on the AC / DC side conversion relationship and the frequency domain models of each small signal quantity, the main circuit small signal frequency domain model includes: Frequency domain small signal model of two-level converter modulation voltage: (twenty one) Where, is the modulation voltage small signal vector, is the PWM gain, is the steady-state vector of the three-phase AC modulation signal, is the DC voltage small signal vector, is the DC voltage steady-state vector, is the small signal vector of the three-phase AC modulation signal; Frequency domain small signal component model of AC circuit: (twenty two) Where, is the modulation voltage small signal vector, is the AC filter inductor impedance under small signal frequency sequence: (twenty three) DC bus frequency domain small signal model: (twenty four) (25) in, is the DC bus capacitance admittance under small signal frequency sequence; Substituting Equation (22) into Equation (24), we can get the DC voltage small signal vector and the small signal vector of phase a AC voltage , a-phase AC current small signal vector The relationship between: (26) Among them, among them, is the transfer matrix between the DC voltage small signal vector and the AC voltage small signal vector, is the transfer matrix between the DC voltage small signal vector and the AC current small signal vector; (27) In one embodiment, a small signal model of a PLL controller is constructed; the three-phase AC voltage is transformed by Park to obtain the AC voltage d-axis and q-axis components, namely: (28) After superimposing the voltage small signal, the AC voltage small signal matrix of phases a, b, and c is 、 and This will result in a phase-locked angular frequency domain small signal vector Convert Equation (29) to the frequency domain, ignore the second-order and above small signal components, and obtain the d-axis and q-axis components of the AC voltage small signal after Park transformation. 、 They are: (29) In Equation (29), the multiplication of two vectors is performed by convolution operation. For the convenience of presentation, the convolution symbol will be omitted here and below. The two-level converter generates the phase-locked angle through PLL control. , as the synchronous rotation reference angle, the phase-locked loop control structure is as follows Figure 2 As shown in the figure, the three-phase AC voltage is transformed into the d-axis and q-axis voltage components respectively through Park transformation, wherein the q-axis voltage component is adjusted by PI and the integral link to generate the phase-locked angle ; Under the control of PLL, the AC voltage small signal disturbance will introduce a small signal component to the phase-locked angle, and the phase-locked angle small signal vector and the q-axis component of the AC voltage small signal The transfer relationship between them is: (30) In the step of constructing the PLL controller small signal model, the DC voltage controller small signal model, and the AC current controller small signal model based on the main circuit small signal frequency domain model, the PLL controller small signal model is: (31) in, is the phase-locking angle small signal vector, is the a-phase AC voltage small signal vector; is the transfer matrix between the phase-locked angle small signal vector and the AC voltage small signal vector; in: (32) Where, is the identity matrix.

[0031] In a specific embodiment, the small signal model of the DC voltage controller is: (33) (34) in, is the AC current small signal d-axis reference instruction, is the DC voltage small signal matrix, is the DC voltage controller transfer function matrix.

[0032] In one embodiment, the small signal model of the AC current controller is: (35) (36) (37) (38) (39) in, 、 are the AC current d and q axis small signal vectors respectively, is the small signal vector of phase a AC voltage , is the small signal of phase a AC current.

[0033] In a specific embodiment, the step of constructing the AC modulation signal small signal model based on the PLL controller small signal model, the DC voltage controller small signal model, and the AC current controller small signal model comprises: according to Figure 4 The small signal d-axis and q-axis components of the AC modulated signal are obtained as follows: (40) in: (41) Substituting equations (36) and (33) into (40), we can obtain the small signal d and q axis vectors of the AC modulated signal 、 The expression is: (42) (43) (44) (45) (46) (47) in, 、 are the small signal d-axis and q-axis vectors of the AC modulated signal respectively; is the small signal vector of phase a AC voltage , is the small signal of phase a AC current; is the DC voltage small signal matrix.

[0034] In a specific embodiment, the d-axis and q-axis components of the AC modulation signal are subjected to an inverse Park transform to obtain a three-phase modulation signal. The small signal vector expression of the a-phase AC modulation signal is: (48) in: (49) (50) (51) In a specific embodiment, in the step of calculating the port impedance of the two-level converter in the scenario of superimposed oscillation component based on the small signal model of the AC modulated signal, the port impedance of the two-level converter is The build steps include: Taking the AC current flowing toward the grid as the reference direction, the AC port admittance of the two-level converter is expressed as: (52) Taking phase a as an example, the small signal vector expression of the modulation voltage of phase a is: (53) in: (54) (55) Substituting equation (53) into equation (22), the AC port impedance of the two-level converter can be obtained as: (56) in, is the small signal vector of phase a AC voltage , is the small signal of phase a AC current, is the identity matrix, is the AC filter inductor impedance under small signal frequency sequence.

[0035] See also Figure 12 As shown, an embodiment of the present invention provides a VSC impedance analysis device in a scenario where an oscillation component is superimposed, including: The first building block is used to superimpose the AC voltage oscillation component and establish a frequency domain model of each steady-state quantity; The second building module is used to establish a steady-state frequency domain model of the main circuit based on the AC / DC side conversion relationship and the frequency domain models of various steady-state quantities; The third building block is used to inject a small signal voltage disturbance into the output terminal of the two-level converter and establish a frequency domain model of each small signal quantity based on the steady-state frequency domain model of the main circuit; The fourth building block is used to establish a main circuit small signal frequency domain model based on the AC / DC side conversion relationship and the frequency domain models of various small signal quantities; A fifth building module is used to build a PLL controller small signal model, a DC voltage controller small signal model, and an AC current controller small signal model based on the main circuit small signal frequency domain model; a sixth building block, configured to build an AC modulation signal small signal model based on the PLL controller small signal model, the DC voltage controller small signal model, and the AC current controller small signal model; The impedance analysis module is used to calculate the port impedance of a two-level converter in a scenario with superimposed oscillation components based on the small signal model of the AC modulated signal.

[0036] See also Figure 13 As shown, an embodiment of the present invention provides an electronic device 100 for implementing a VSC impedance analysis method in a superimposed oscillation component scenario; the electronic device 100 includes 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.

[0037] The memory 101 can be used to store the computer program 103. The processor 102 implements the steps of the VSC impedance analysis method in a superimposed oscillation component scenario described in the embodiment by running or executing the computer program stored in the memory 101 and calling the data stored in the memory 101. The memory 101 can mainly include a program storage area and a data storage area. The program storage area can store an operating system and at least one application required for a function (such as a sound playback function, an image playback function, etc.); the data storage area can store data (such as audio data) created based on the use of the electronic device 100. 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.

[0038] The at least one processor 102 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The processor 102 may be a microprocessor or any conventional processor, etc. The processor 102 is the control center of the electronic device 100 and connects various parts of the entire electronic device 100 using various interfaces and lines.

[0039] The memory 101 in the electronic device 100 stores a plurality of instructions for implementing a VSC impedance analysis method in a scenario where an oscillation component is superimposed. The processor 102 may execute the plurality of instructions to implement: The AC voltage oscillation component is superimposed to establish the frequency domain models of each steady-state quantity; based on the AC / DC side conversion relationship and the frequency domain models of each steady-state quantity, a steady-state frequency domain model of the main circuit is established; a small-signal voltage disturbance is injected at the output end of the two-level converter, and the frequency domain models of each small-signal quantity are established based on the steady-state frequency domain model of the main circuit; based on the AC / DC side conversion relationship and the frequency domain models of each small-signal quantity, a small-signal frequency domain model of the main circuit is established; based on the small-signal frequency domain model of the main circuit, a PLL controller small-signal model, a DC voltage controller small-signal model and an AC current controller small-signal model are constructed; based on the PLL controller small-signal model, the DC voltage controller small-signal model and the AC current controller small-signal model, an AC modulation signal small-signal model is constructed; based on the AC modulation signal small-signal model, the port impedance of the two-level converter in the scenario of superimposed oscillation components is calculated.

[0040] If the module / unit integrated in the electronic device 100 is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the process in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory and read-only memory (ROM, Read-Only Memory).

Claims

1. A VSC impedance analysis method in a scenario with superimposed oscillation components, characterized in that: include: Superimpose the AC voltage oscillation component and establish the frequency domain model of each steady-state quantity; According to the AC / DC side transformation relationship and the frequency domain models of various steady-state quantities, a steady-state frequency domain model of the main circuit is established; Small signal voltage disturbances are injected into the output of the two-level converter to establish frequency domain models of each small signal quantity. According to the AC / DC side conversion relationship and the frequency domain models of various small signal quantities, the main circuit small signal frequency domain model is established; Based on the control structure of each controller, the small signal model of the PLL controller, the small signal model of the DC voltage controller and the small signal model of the AC current controller are constructed; Based on the PLL controller small signal model, DC voltage controller small signal model and AC current controller small signal model, a small signal model of AC modulation signal is constructed; The port impedance of a two-level converter in a scenario with superimposed oscillation components is calculated based on the small signal model of the AC modulated signal and the small signal frequency domain model of the main circuit.

2. The VSC impedance analysis method in a superimposed oscillation component scenario according to claim 1 is characterized in that: The step of superimposing the AC voltage oscillation component and establishing the frequency domain model of each steady-state quantity specifically includes: The frequency superimposed on the fundamental frequency component of the AC voltage of the two-level converter is The AC voltage oscillation component, the fundamental frequency is ; Two-level converter contains fundamental frequency and oscillation frequency The steady-state component also contains the linear combination frequency The steady-state component of , ; h 、 k They are and The coefficient of , g is the highest number of iterations considered; the steady-state frequency sequence matrix of the three-phase AC component is obtained: （1） Steady-state frequency sequence matrix of the DC component: （2） The frequency domain steady-state operating point of the b and c phase sine and cosine functions: （7） Where, is the steady-state phase sequence coefficient matrix, is a sine function The steady-state quantity, is the cosine function The steady-state quantity, 、 The sine functions 、 The steady-state quantity, 、 The cosine function 、 The steady-state quantity of is the phase-locking angle; Steady-state quantities of the d-axis and q-axis components of AC voltage: （8） Where, 、 are the steady-state quantities of the d-axis and q-axis components of the AC voltage respectively; is the steady-state value of phase a AC voltage, is the steady-state value of phase b AC voltage, is the steady-state value of phase c AC voltage; 、 It is calculated based on the Toplitz matrix expansion method established according to the frequency domain convolution theorem.

3. The VSC impedance analysis method in a superimposed oscillation component scenario according to claim 1, characterized in that: The step of establishing the main circuit steady-state frequency domain model according to the AC / DC side conversion relationship and the frequency domain model of each steady-state quantity specifically includes: calculating the three-phase modulation voltage steady-state quantity according to the AC / DC voltage and current relationship of the two-level converter. , DC voltage steady-state quantity , steady-state quantity of three-phase AC modulation signal The relationship between: （9） Where, K m is the PWM gain; Frequency domain steady-state model of the two-level converter AC circuit: （10） Where, is the AC filter inductor impedance under steady-state frequency sequence; The DC bus frequency domain steady-state model expression is: （12） Where, is the steady-state DC current, is the steady-state quantity of DC capacitance.

4. The VSC impedance analysis method in a superimposed oscillation component scenario according to claim 1, characterized in that: In the step of injecting a small signal voltage disturbance at the output end of the two-level converter and establishing each small signal quantity frequency domain model based on the steady-state frequency domain model of the main circuit, each small signal quantity frequency domain model includes: Small signal frequency sequence matrix of three-phase AC components: （15） Small signal frequency sequence matrix of DC component: （16） Small signal vectors of phase b and c AC voltage, AC current, and AC modulation signals: （19） in, is the a-phase AC voltage small signal vector, is the b-phase AC voltage small signal vector, is the c-phase AC voltage small signal vector, is the small signal vector phase sequence coefficient matrix; is the small signal vector of the a-phase AC modulation signal, is the small signal vector of the b-phase AC modulation signal, is the small signal vector of the c-phase AC modulation signal.

5. The VSC impedance analysis method in a superimposed oscillation component scenario according to claim 1, characterized in that: In the step of establishing a main circuit small signal frequency domain model based on the AC / DC side conversion relationship and the frequency domain models of each small signal quantity, the main circuit small signal frequency domain model includes: Frequency domain small signal model of two-level converter modulation voltage: （21） Where, is the modulation voltage small signal vector, is the PWM gain, is the steady-state vector of the three-phase AC modulation signal, is the DC voltage small signal vector, is the DC voltage steady-state vector, is the small signal vector of the three-phase AC modulation signal; Frequency domain small signal component model of AC circuit: （23） Where, is the modulation voltage small signal vector, is the AC filter inductor impedance under small signal frequency sequence; DC bus frequency domain small signal model: （25） in, is the DC bus capacitance admittance under small signal frequency sequence; Substituting Equation (23) into Equation (25), we can get the DC voltage small signal vector and the small signal vector of phase a AC voltage , a-phase AC current small signal vector The relationship between: （27） in, is the transfer matrix between the DC voltage small signal vector and the AC voltage small signal vector, is the transfer matrix between the DC voltage small signal vector and the AC current small signal vector.

6. The VSC impedance analysis method in a superimposed oscillation component scenario according to claim 1, characterized in that: In the step of constructing the PLL controller small signal model, the DC voltage controller small signal model, and the AC current controller small signal model based on the main circuit small signal frequency domain model, the PLL controller small signal model is: （32） in, is the phase-locking angle small signal vector, is the a-phase AC voltage small signal vector; is the transfer matrix between the phase-locked angle small signal vector and the AC voltage small signal vector; The small signal model of the DC voltage controller is: （34） in, is the AC current small signal d-axis reference instruction, is the DC voltage small signal matrix, is the transfer function matrix of the DC voltage controller; The small signal model of the AC current controller is: （36） in, 、 are the AC current d and q axis small signal vectors respectively, is the small signal vector of phase a AC voltage , is the small signal of phase a AC current; is the transfer matrix between the AC current d-axis small signal vector and the AC voltage small signal vector, is the transfer matrix between the AC current d-axis small signal vector and the AC current small signal vector, is the transfer matrix between the AC current q-axis small signal vector and the AC voltage small signal vector, is the transfer matrix between the AC current q-axis small signal vector and the AC current small signal vector.

7. The VSC impedance analysis method in a superimposed oscillation component scenario according to claim 1, characterized in that: In the step of constructing an AC modulation signal small signal model based on the PLL controller small signal model, the DC voltage controller small signal model, and the AC current controller small signal model, the AC modulation signal small signal model is: （49） in, is the AC modulated signal vector; is the small signal vector of phase a AC voltage , is the small signal of phase a AC current; is the DC voltage small signal matrix; is the transfer matrix between the AC modulated signal small signal vector and the AC voltage small signal vector; is the transfer matrix between the AC modulated signal small signal vector and the AC current small signal vector; is the transfer matrix between the AC modulation signal small signal vector and the DC voltage small signal vector.

8. The VSC impedance analysis method in a superimposed oscillation component scenario according to claim 1, characterized in that: In the step of calculating the port impedance of the two-level converter in the scenario of superimposed oscillation component based on the small signal model of the AC modulated signal, the port impedance of the two-level converter is for: （57） in, is the small signal vector of phase a AC voltage , is the small signal of phase a AC current, is the identity matrix, is the AC filter inductor impedance under small signal frequency sequence, is the transfer matrix between the AC modulated voltage small signal vector and the AC voltage small signal vector, is the transfer matrix between the AC modulated voltage small signal vector and the AC current small signal vector.

9. A VSC impedance analysis device in a scenario with superimposed oscillation components, characterized in that: include: The first building block is used to superimpose the AC voltage oscillation component and establish a frequency domain model of each steady-state quantity; The second building module is used to establish a steady-state frequency domain model of the main circuit based on the AC / DC side conversion relationship and the frequency domain models of various steady-state quantities; The third building block is used to inject a small signal voltage disturbance into the output terminal of the two-level converter and establish a frequency domain model of each small signal quantity; The fourth building block is used to establish a main circuit small signal frequency domain model based on the AC / DC side conversion relationship and the frequency domain models of various small signal quantities; a fifth building module, configured to build a PLL controller small signal model, a DC voltage controller small signal model, and an AC current controller small signal model based on the control structures of the controllers; a sixth building block, configured to build an AC modulation signal small signal model based on the PLL controller small signal model, the DC voltage controller small signal model, and the AC current controller small signal model; The impedance analysis module is used to calculate the port impedance of the two-level converter in the scenario of superimposed oscillation components based on the small signal model of the AC modulation signal and the small signal frequency domain model of the main circuit.

10. 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 a VSC impedance analysis method in a scenario with a superimposed oscillation component as claimed in any one of claims 1 to 8.

11. 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 VSC impedance analysis method in a scenario with a superimposed oscillation component according to any one of claims 1 to 8 is implemented.

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