Converter switching circuit dynamic modeling method and device for broadband oscillation analysis and medium

Abstract

The invention relates to a converter switching circuit dynamic modeling method and device for broadband oscillation analysis and a medium, and the method comprises the steps: building state-space equations of a converter rectification side before and after commutation and during commutation under a dq coordinate system, and obtaining a transition equation of a commutation starting moment and a commutation ending moment according to a commutation time sequence; a discrete sampling-data modeling method is adopted to obtain a mathematical model of the rectification side of the converter, and a small signal discrete equation corresponding to the rectification side is obtained after linearization; obtaining a small signal discrete equation corresponding to the inverter side in the same way; and obtaining a small signal model of the main circuit of the converter according to the state equation combination of the rectifier side, the inverter side and the direct current capacitor of the converter. Compared with the prior art, the converter switching circuit dynamic modeling method designed by the invention can effectively consider the dynamic characteristics of the converter, and is suitable for a relatively high frequency range.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and in particular to a method, equipment and medium for dynamic modeling of a converter switch circuit for broadband oscillation analysis. Background Art

[0002] With the increasing application of converter systems in my country, the study of their operating characteristics, especially their dynamic characteristics, is very urgent and important. The steady-state process of the converter system is easy to understand, but for stability analysis involving higher frequency modes, it is necessary to accurately describe the dynamic characteristics of the converter system.

[0003] The quasi-steady-state model of the converter system is a widely used analytical model, which is widely used in low-frequency small signal characteristic root analysis and electromechanical transient simulation. In the quasi-steady-state model, the converter adopts a fundamental frequency steady-state model, and the voltage and current relationship between the AC side and the DC side is described by a steady-state equation, which is derived under the assumption that the DC current is constant, ignoring the dynamic characteristics of the converter switch circuit.

[0004] The problems of low-order harmonic instability and subsynchronous oscillation in the converter system are essentially small disturbance problems. They can be analyzed by linearizing the entire system near the operating point to transform it into a linear system, such as the characteristic root method. The prior art uses the fundamental frequency steady-state model of the converter to perform characteristic root analysis on the high-frequency dynamic characteristics of the converter system. However, since the fundamental frequency steady-state model of the converter is only an average value model for the fundamental wave quantity, it does not consider the instantaneous topological structure changes of the system and the dynamic performance of the thyristor switching. When analyzing the dynamic stability of the system, especially when the oscillation frequency is high, whether this model is applicable is still controversial. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method, device and medium for dynamic modeling of converter switching circuit for wide-band oscillation analysis, which can effectively take into account the dynamic characteristics of the converter and is suitable for a higher frequency range.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] According to a first aspect of the present invention, there is provided a method for dynamic modeling of a converter switch circuit for broadband oscillation analysis, the method comprising:

[0008] The state space equation of the rectifier side of the converter before, during and after commutation is established in the dq coordinate system. The transition equations at the start and end of commutation are obtained according to the commutation timing. The mathematical model of the rectifier side of the converter is obtained by using the discrete sampling-data modeling method. After linearization, the corresponding small signal discrete equation of the rectifier side is obtained.

[0009] The state space equations of the inverter side of the converter before, during and after commutation are established in the dq coordinate system. The transition equations at the start and end of commutation are obtained according to the commutation timing. The mathematical model of the inverter side of the converter is obtained by using the discrete sampling-data modeling method. After linearization, the corresponding small signal discrete equation of the inverter side is obtained.

[0010] The small signal discrete equations of the converter rectifier side, inverter side and DC capacitor are combined to obtain the small signal model of the converter main circuit.

[0011] Preferably, the converter switch circuit includes a rectifying and measuring circuit, an inverter side circuit and a DC transmission line, the DC transmission line is represented by a T-type equivalent circuit, and the rectifying and measuring circuit and the inverter side circuit are both provided with resistance, inductance, capacitance and leakage reactance.

[0012] Preferably, in the normal working mode of the converter, the state space equations of the rectifier side and the inverter side of the converter before and after commutation and during commutation are established, and the state space equations of the rectifier side of the converter before and after commutation and during commutation are specifically:

[0013] The state space equation of the rectifier side of the converter before commutation on the rectifier side:

[0014]

[0015] Where: Y1 is the state variable before commutation on the rectifier side, B u1 is the coefficient matrix of voltage in the dq coordinate system, B ud1 is the coefficient matrix of the voltage d-axis component in the dq coordinate system, A1, T1 and W are coefficient matrices, θ is the phase angle, U dq is the AC voltage in the dq coordinate system, U d is the capacitance C d Voltage across both ends;

[0016] The state space equation of the rectifier side of the converter during commutation on the rectifier side:

[0017]

[0018] Where: X is the state variable during the commutation period of the rectifier side, A, B u and B ud is the coefficient matrix;

[0019] The state space equation of the rectifier side of the converter after commutation on the rectifier side:

[0020]

[0021] Where: Y2 is the state variable after commutation on the rectifier side, and T2 is the coefficient matrix.

[0022] Preferably, the transition equations for the start and end times of the commutation are obtained according to the commutation timing, specifically:

[0023] The transition equation at the start of commutation:

[0024]

[0025] Where: σ is the starting time of commutation, Q is the coefficient matrix;

[0026] Transition equation at the end of commutation:

[0027]

[0028] Where: φ is the end time of commutation, L s is the leakage reactance of the converter, L d is the inductance of the converter, and P is the coefficient matrix.

[0029] Preferably, the mathematical model of the rectifier side of the converter is obtained by using the discrete sampling-data modeling method, specifically:

[0030] Sampling at any time t0 before commutation, the corresponding state quantity I d (t0), after π / 3 cycles, sampling is performed at time t1 to obtain the corresponding state quantity I d (t1);

[0031] The system state quantity Y2(t1) at time t1 is expressed mathematically as:

[0032]

[0033] get

[0034] Y2(t1)=H0(Y1(t0),U dq ,α,U d ,φ,θ0,ω)

[0035] Where: H0 is the functional relationship, α is the rectifier trigger angle, θ0 is the phase angle of phase A, ω is the power frequency, represents the angle between the d-axis and the A phase;

[0036] The linearization of Y2(t1) at the sampling point at time t0 is:

[0037]

[0038] Where: ΔY2(t1) is the system state at time t1, ΔY1(t0) is the system state at time t0, F is the coefficient matrix, G is the coefficient matrix, ΔU dq(t0) is the differential value of the AC voltage in the dq coordinate system at time t0, H is the coefficient matrix, Δα is the differential value of the rectifier firing angle, I is the coefficient matrix, ΔU d is the differential of the voltage across capacitor Cd, J is the coefficient matrix, Δθ0 is the differential of the phase angle of phase A, K is the coefficient matrix, Δω is the differential of the power frequency change;

[0039]

[0040] The AC current I in dq coordinates at time t0 dq (t0) is:

[0041] I dq (t0)=V(t0)I abc (t0)=V(t0)S1I d (t0)

[0042] Where: I abc is the AC input current, S1 is the coefficient matrix, S1=T1 T , I d is the phase-to-phase current.

[0043] Preferably, the small signal discrete equation corresponding to the rectifier side is obtained after the linearization, specifically:

[0044]

[0045] Where: ΔI dr is the phase-to-phase current on the rectifier side, ΔI dq_r is the differential value of the AC current in the rectifier side dq coordinate system, A r , B r1 , B r2 , B r3 , B r4 , B r5 , C r and D r are all coefficient matrices, and Δθ is the phase angle change.

[0046] Preferably, the small signal discrete equation of the DC capacitor is specifically:

[0047]

[0048] Where: ΔU d is the differential voltage across capacitor Cd, ΔI dr is the phase-to-phase current on the rectifier side, C d is the capacitance, ΔI di is the phase-to-phase current on the inverter side.

[0049] Preferably, the small signal model of the converter main circuit is expressed as follows:

[0050]

[0051] Wherein: subscripts r and i correspond to the rectifier and inverter sides respectively.

[0052] According to a second aspect of the present invention, there is provided an electronic device, comprising a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the program, any one of the methods described above is implemented.

[0053] According to a third aspect of the present invention, there is provided a computer-readable storage medium having a computer program stored thereon, wherein when the program is executed by a processor, any one of the methods described above is implemented.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] The converter modeling method proposed in the present invention establishes the state space equation of the converter rectifier side before, during and after commutation in the dq coordinate system, obtains the transition equations at the start and end of the commutation according to the commutation timing, adopts the discrete sampling-data modeling method to obtain the mathematical model of the converter rectifier side, obtains the corresponding small signal discrete equation of the rectifier side after linearization, and obtains the corresponding small signal discrete equation of the inverter side in the same way; according to the combination of the state equations of the converter rectifier side, the inverter side and the DC capacitor, the small signal model of the converter main circuit is obtained, which can effectively take into account the dynamic characteristics of the converter, is suitable for a higher frequency range, and has application value in practical engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a flow chart of the method of the present invention;

[0057] Figure 2 is a schematic diagram of the main circuit of the converter;

[0058] Figure 3 It is the equivalent circuit diagram of the rectifier side;

[0059] Figure 4 is the equivalent circuit before commutation;

[0060] Figure 5 is the equivalent circuit during commutation;

[0061] Figure 6 is the commutation process timing;

[0062] Figure 7 is the AC three-phase voltage and sampling point location;

[0063] Figure 8Time domain simulation comparison of the detailed model and the linearized model. DETAILED DESCRIPTION

[0064] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0065] Example 1

[0066] like Figure 1 As shown, this embodiment provides a method for dynamic modeling of a converter switch circuit suitable for wide-band oscillation analysis, the method comprising:

[0067] The state space equation of the rectifier side of the converter before, during and after commutation is established in the dq coordinate system. The transition equations at the start and end of commutation are obtained according to the commutation timing. The mathematical model of the rectifier side of the converter is obtained by using the discrete sampling-data modeling method. After linearization, the corresponding small signal discrete equation of the rectifier side is obtained.

[0068] The state space equations of the inverter side of the converter before, during and after commutation are established in the dq coordinate system. The transition equations at the start and end of commutation are obtained according to the commutation timing. The mathematical model of the inverter side of the converter is obtained by using the discrete sampling-data modeling method. After linearization, the corresponding small signal discrete equation of the inverter side is obtained.

[0069] The small signal discrete equations of the converter rectifier side, inverter side and DC capacitor are combined to obtain the small signal model of the converter main circuit.

[0070] The electronic device of the present invention includes a central processing unit (CPU), which can perform various appropriate actions and processes according to computer program instructions stored in a read-only memory (ROM) or loaded from a storage unit into a random access memory (RAM). In the RAM, various programs and data required for device operation can also be stored. The CPU, ROM and RAM are connected to each other via a bus. An input / output (I / O) interface is also connected to the bus.

[0071] Multiple components in the device are connected to the I / O interface, including: input units, such as keyboards, mice, etc.; output units, such as various types of displays, speakers, etc.; storage units, such as disks, optical disks, etc.; and communication units, such as network cards, modems, wireless communication transceivers, etc. The communication unit allows the device to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunication networks.

[0072] The processing unit performs the various methods and processes described above. For example, in some embodiments, methods S1 to S4 may be implemented as a computer software program, which is tangibly contained in a machine-readable medium, such as a storage unit. In some embodiments, part or all of the computer program may be loaded and / or installed on the device via a ROM and / or a communication unit. When the computer program is loaded into the RAM and executed by the CPU, one or more steps of the method described above may be performed. Alternatively, in other embodiments, the CPU may be configured to execute the method in any other appropriate manner (e.g., by means of firmware).

[0073] The functions described above herein may be performed at least in part by one or more hardware logic components. For example, without limitation, exemplary types of hardware logic components that may be used include: field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chip systems (SOCs), load programmable logic devices (CPLDs), and the like.

[0074] The program code for implementing the method of the present invention can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that the program code, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The program code can be executed entirely on the machine, partially on the machine, partially on the machine as a stand-alone software package and partially on a remote machine, or entirely on a remote machine or server.

[0075] In the context of the present invention, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0076] Example 2

[0077] like Figure 1As shown, this embodiment provides a method for dynamic modeling of a converter switch circuit suitable for wide-band oscillation analysis, the method comprising:

[0078] The state space equation of the rectifier side of the converter before, during and after commutation is established in the dq coordinate system. The transition equations at the start and end of commutation are obtained according to the commutation timing. The mathematical model of the rectifier side of the converter is obtained by using the discrete sampling-data modeling method. After linearization, the corresponding small signal discrete equation of the rectifier side is obtained.

[0079] The state space equations of the inverter side of the converter before, during and after commutation are established in the dq coordinate system. The transition equations at the start and end of commutation are obtained according to the commutation timing. The mathematical model of the inverter side of the converter is obtained by using the discrete sampling-data modeling method. After linearization, the corresponding small signal discrete equation of the inverter side is obtained.

[0080] The small signal discrete equations of the converter rectifier side, inverter side and DC capacitor are combined to obtain the small signal model of the converter main circuit.

[0081] Next, the method of this embodiment is introduced in detail.

[0082] The main circuit diagram of the converter system is as follows: Figure 2 As shown in the figure, it consists of three parts: rectifier, inverter and DC transmission line. Figure 2 In the figure, the left and right sides of the dotted line correspond to the rectifier side and the inverter side. The DC line is represented by a T-type equivalent circuit. Rd, Ld, and Cd are the corresponding resistance, inductance, and capacitance, respectively, where Ld includes the role of the smoothing reactor. Ls is the leakage reactance of the converter transformer. By modeling the rectifier side and the inverter side separately, the corresponding two state equations are obtained, and combined with the state equation of the DC capacitor Cd, the small signal model of the entire converter main circuit is obtained.

[0083] This embodiment takes a single-bridge 6-pulse converter as an example and adopts an equidistant pulse triggering mode. Only the converter is considered to work in a normal working mode with a commutation angle less than 60°, that is, three valves are turned on during the commutation process and two valves are turned on during the non-commutation period.

[0084] like Figure 3 The equivalent circuit diagram of the rectifier side shown is analyzed by taking the commutation process of valves 6, 1, and 2 as an example.

[0085] Through Park transformation, the AC input voltage U ab c In dq coordinates it can be expressed as:

[0086]

[0087] The AC voltage uses dq coordinates to facilitate the interface with external systems.

[0088] The circuit before commutation is as follows Figure 4 As shown, at this time, valve 6 is connected to valve 1, and the circuit state equation is

[0089]

[0090] or

[0091]

[0092] Where: Y1 is the state variable before commutation on the rectifier side, B u1 is the coefficient matrix of voltage in the dq coordinate system, B ud1 is the coefficient matrix of the voltage d-axis component in the dq coordinate system, A1, T1 and W are coefficient matrices, θ is the phase angle, U dq is the AC voltage in the dq coordinate system, U d is the capacitance C d The voltage at both ends, the specific coefficient matrix is ​​set as follows

[0093]

[0094] The equivalent circuit diagram during commutation is as follows Figure 5 As shown, at this time, valves 6, 1 and 2 are connected, and the corresponding circuit state equation is:

[0095]

[0096] or

[0097]

[0098] Where: X is the state variable during the commutation period of the rectifier side, A, B u and B ud is the coefficient matrix, and the coefficient matrix is ​​specifically set as follows

[0099]

[0100] The circuit diagram after commutation is completed Figure 4 The circuit diagram before commutation is similar, except that the conduction valves are valve 1 and valve 2, and the corresponding circuit state equation is:

[0101]

[0102] Wherein: Y2 is the state variable after commutation on the rectifier side, T2 is the coefficient matrix, and in this embodiment, T2=(1 0 -1).

[0103] Figure 6 The timing of the commutation process is shown in Figure 1. In the figure, σ and φ represent the starting and ending time of the commutation, respectively. ω0 is the power frequency. The transition equation at the starting time of the commutation is:

[0104]

[0105] Where: Q is the coefficient matrix.

[0106] Transition equation at the end of commutation:

[0107]

[0108] Where: φ is the end time of commutation, L s is the leakage reactance of the converter, L d is the inductance of the converter, and P is the coefficient matrix.

[0109] For a single-bridge converter, the six bridge valves are triggered in turn at equal intervals of π / 3 cycles. d The period is π / 3.

[0110] Discrete Sampling - Data Modeling:

[0111] Sampling is performed at a certain time t0 before commutation to obtain the corresponding state quantity I d (t0), after π / 3 cycles, sampling is performed again to obtain the state quantity I d (t1). System state I at time t1 d (t1) is the state variable I at time t0 d (t0) is determined by the corresponding external input, which includes the commutation start time σ, the commutation end time φ, the AC voltage U dq , DC voltage U d and the system synchronization reference angle θ. The corresponding small signal discrete equation is obtained by linearization. Figure 6 The timing of the commutation process.

[0112] The system state at time t1 is Y2(t1):

[0113]

[0114] in: Represents the angle between the d-axis and the A-phase.

[0115] Figure 7 is the AC three-phase voltage and sampling point position, the reference time point t = 0 and the position of the sampling points t0 and t1. In the figure, α represents the trigger angle of the rectifier. As can be seen from the figure, t0 = 0,

[0116] Y2(t1) is Y1(t0), U dq ,α,U d , φ, θ0 and ω, that is

[0117] Y2(t1)=H0(Y1(t0),U dq ,α,U d ,φ,θ0,ω) (10)

[0118] Where: H0 is the functional relationship, α is the rectifier trigger angle, θ0 is the phase angle of phase A, ω is the power frequency, Represents the angle between the d-axis and the A-phase.

[0119] Linearize the above equation at sampling point t0 and get:

[0120]

[0121] Where: ΔY2(t1) is the system state at time t1, ΔY1(t0) is the system state at time t0, F is the coefficient matrix, G is the coefficient matrix, ΔU dq (t0) is the differential value of the AC voltage in the dq coordinate system at time t0, H is the coefficient matrix, Δα is the differential value of the rectifier firing angle, I is the coefficient matrix, ΔU d is the differential of the voltage across capacitor Cd, J is the coefficient matrix, Δθ0 is the differential of the phase angle of phase A, K is the coefficient matrix, Δω is the differential of the power frequency change;

[0122]

[0123] Note that PB u T=B u1 T2, PB ud =B ud1 ,therefore Therefore, in the following derivation, the term related to Δφ is no longer written out.

[0124] The AC current at time t0 in dq coordinates is:

[0125] I dq (t0)=V(t0)I abc (t0)=V(t0)S1I d (t0) (12)

[0126] Where: I abc is the AC input current, S1 is the coefficient matrix, S1=T1 T , I d is the phase-to-phase current.

[0127] After linearization, we get:

[0128] ΔI dq (t0) = LΔI d (t0)+MΔθ0 (13)

[0129] in

[0130] L=V(t0)S1

[0131]

[0132] S1=T1 T

[0133] The entire discretized equation is written as:

[0134]

[0135] Where: subscript r corresponds to the rectifier side.

[0136] By making equation (14) continuous, we can obtain the continuous state equation:

[0137]

[0138] Where: ΔI dr is the phase-to-phase current on the rectifier side, ΔI dq_r is the differential value of the AC current in the rectifier side dq coordinate system, A r , B r1 , B r2 , B r3 , B r4 , B r5 , C r and D r are all coefficient matrices, Δθ is the phase angle change, and the specific settings are as follows

[0139]

[0140] B r4 =(F-1) -1 A r J,B r5 =(F-1) -1 A r K

[0141] C r =L,D r =M

[0142] Where: ΔT represents the sampling period.

[0143] The inverter side is modeled and the corresponding inverter side state equation is obtained (the trigger phase angle of the inverter side is represented by the leading angle β):

[0144]

[0145] Capacitor C d The state equation is

[0146]

[0147] Combining equations (15), (16) and (17), we get the small signal model of the converter main circuit:

[0148]

[0149] Wherein: subscripts r and i correspond to the rectifier and inverter sides respectively.

[0150] Verification example: Compare the time domain response of the detailed model of the converter system and the small signal linearization model to the external input disturbance. The system parameters adopt the first reference system model parameters of the converter, and the AC system on both sides of the converter is equivalent to the ideal voltage source U r =426.9kV, U i =400kV (line voltage, effective value), the system reference frequency is 60Hz.

[0151] The parameters are as follows:

[0152] L d =0.5968HR d =2.5Ω

[0153] L s =0.0721HC d =26.0uF

[0154] In order to test the dynamic characteristics of the converter main circuit, the control loop of the rectifier and the inverter is not considered, so the trigger angles of the rectifier and the inverter are kept at constant values: α0 = 10°, β0 = 36°.

[0155] The coefficients of the linear system model corresponding to equation (18) are:

[0156] A r =-40.4003,B r1 =(2.2808-0.3841),B r2 =-1.5531×10 5 ,B r3 =-1.5969,B r4 =-1.4973×10 5 ,B r5 =5.0208×10 5

[0157] A i =-40.4003,B i1 =(-1.91120.4224),B i2 =5.3074×10 5 ,B i3 =1.6141,B i4=7.3328×10 5 ,B i5 =-2.1751×10 5

[0158]

[0159] When the rectifier trigger angle α changes from 10° to 12°, I dr , U d ,I di The time domain responses corresponding to the detailed model and the linearized model respectively, the linearized model can still reflect the dynamic characteristics of the entire converter main circuit.

[0160] When using the sampling-data method to model, sampling is performed every 1 / 6 of the power frequency cycle. According to the sampling theorem, the applicable frequency of the model is 0 to 3 times the power frequency cycle (relative to the DC side), so the model is fully applicable to the analysis of system dynamic stability in a higher frequency range, such as SSO characteristic analysis and low-order harmonic instability analysis.

[0161] Figure 8 1 is a comparison of the time domain simulation results of the method of the present invention and the linearized model, wherein (a), (b) and (c) correspond to the DC current on the rectifier side, the DC current at the midpoint of the DC line and the DC current on the inverter side, respectively.

[0162] The converter modeling method proposed in the present invention can effectively take into account the dynamic characteristics of the converter and is applicable to a higher frequency range.

[0163] The other configurations of this embodiment are the same as those of Embodiment 1.

[0164] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for dynamic modeling of a converter switching circuit for broadband oscillation analysis, characterized in that: The method includes: The state space equation of the rectifier side of the converter before, during and after commutation is established in the dq coordinate system. The transition equations at the start and end of commutation are obtained according to the commutation timing. The mathematical model of the rectifier side of the converter is obtained by using the discrete sampling-data modeling method. After linearization, the corresponding small signal discrete equation of the rectifier side is obtained. The state space equations of the inverter side of the converter before, during and after commutation are established in the dq coordinate system. The transition equations at the start and end of commutation are obtained according to the commutation timing. The mathematical model of the inverter side of the converter is obtained by using the discrete sampling-data modeling method. After linearization, the corresponding small signal discrete equation of the inverter side is obtained. The small signal discrete equations of the converter rectifier side, inverter side and DC capacitor are combined to obtain the small signal model of the converter main circuit.

2. A method for dynamic modeling of a converter switch circuit for broadband oscillation analysis according to claim 1, characterized in that: The converter switch circuit includes a rectifying and measuring circuit, an inverter side circuit and a DC transmission line. The DC transmission line is represented by a T-type equivalent circuit. The rectifying and measuring circuit and the inverter side circuit are both provided with resistance, inductance, capacitance and leakage reactance.

3. A method for dynamic modeling of a converter switch circuit for broadband oscillation analysis according to claim 1, characterized in that: Under the normal working mode of the converter, the state space equations of the rectifier side and the inverter side of the converter before and after commutation and during commutation are established. The state space equations of the rectifier side of the converter before and after commutation and during commutation are specifically: The state space equation of the rectifier side of the converter before commutation on the rectifier side: Where: Y1 is the state variable before commutation on the rectifier side, B u1 is the coefficient matrix of voltage in the dq coordinate system, B ud1 is the coefficient matrix of the voltage d-axis component in the dq coordinate system, A1, T1 and W are coefficient matrices, θ is the phase angle, U dq is the AC voltage in the dq coordinate system, U d is the capacitance C d Voltage across both ends; The state space equation of the rectifier side of the converter during commutation on the rectifier side: Where: X is the state variable during the commutation period of the rectifier side, A, B u and B ud is the coefficient matrix; The state space equation of the rectifier side of the converter after commutation on the rectifier side: Where: Y2 is the state variable after commutation on the rectifier side, and T2 is the coefficient matrix.

4. A method for dynamic modeling of a converter switch circuit for broadband oscillation analysis according to claim 3, characterized in that: The transition equations for the start and end times of commutation are obtained according to the commutation timing, specifically: The transition equation at the start of commutation: Where: σ is the starting time of commutation, Q is the coefficient matrix; Transition equation at the end of commutation: Where: φ is the end time of commutation, L s is the leakage reactance of the converter, L d is the inductance of the converter, and P is the coefficient matrix.

5. A method for dynamic modeling of a converter switch circuit for broadband oscillation analysis according to claim 4, characterized in that: The mathematical model of the converter rectifier side is obtained by using the discrete sampling-data modeling method, specifically: Sampling at any time t0 before commutation, the corresponding state quantity I d (t0), after π / 3 cycles, sampling is performed at time t1 to obtain the corresponding state quantity I d (t1); The system state quantity Y2(t1) at time t1 is expressed mathematically as follows: get Y2(t1)=H0(Y1(t0),U dq ,a,U d ,φ,θ0,ω) Where: H0 is the functional relationship, α is the rectifier trigger angle, θ0 is the phase angle of phase A, ω is the power frequency, represents the angle between the d-axis and the A phase; The linearization of Y2(t1) at the sampling point at time t0 is: Where: ΔY2(t1) is the system state at time t1, ΔY1(t0) is the system state at time t0, F is the coefficient matrix, G is the coefficient matrix, ΔU dq (t0) is the differential value of the AC voltage in the dq coordinate system at time t0, H is the coefficient matrix, Δα is the differential value of the rectifier firing angle, I is the coefficient matrix, ΔU d is the differential of the voltage across capacitor Cd, J is the coefficient matrix, Δθ0 is the differential of the phase angle of phase A, K is the coefficient matrix, Δω is the differential of the power frequency change; The AC current I in dq coordinates at time t0 dq (t0) is: I dq (t0)=V(t0)I abc (t0)=V(t0)S1I d (t0) Where: I abc is the AC input current, S1 is the coefficient matrix, S1=T1 T , I d is the phase-to-phase current.

6. A method for dynamic modeling of a converter switch circuit for broadband oscillation analysis according to claim 5, characterized in that: After the linearization, the corresponding small signal discrete equation on the rectifier side is obtained, which is specifically: Where: ΔI dr is the phase-to-phase current on the rectifier side, ΔI dq_r is the differential value of the AC current in the rectifier side dq coordinate system, A r , B r1 , B r2 , B r3 , B r4 , B r5 , C r and D r are all coefficient matrices, and Δθ is the phase angle change.

7. A method for dynamic modeling of a converter switch circuit for broadband oscillation analysis according to claim 6, characterized in that: The small signal discrete equation of the DC capacitor is specifically: Where: ΔU d is the differential voltage across capacitor Cd, ΔI dr is the phase-to-phase current on the rectifier side, C d is the capacitance, ΔI di is the phase-to-phase current on the inverter side.

8. A method for dynamic modeling of a converter switch circuit for broadband oscillation analysis according to claim 7, characterized in that: The small signal model of the converter main circuit is expressed as follows: Wherein: subscripts r and i correspond to the rectifier and inverter sides respectively.

9. An electronic device comprising a memory and a processor, wherein a computer program is stored in the memory, wherein: When the processor executes the program, the method according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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