A method for evaluating and analyzing grid-connected harmonic resonance of voltage source converters

Abstract

The present invention provides a voltage source converter grid-connected harmonic resonance evaluation and analysis method. The method divides the harmonic response closed-loop process of the voltage source converter into four processes, and establishes a harmonic model considering the harmonic coupling effect. The harmonic coupling admittance is obtained according to the harmonic model, and then the harmonic admittance matrix representing the frequency coupling effect is obtained. The process repeatedly considers the frequency coupling situation, and then uses a singular value decomposition algorithm to perform data dimension reduction on the harmonic admittance matrix representing the frequency coupling effect, extracts the main features, and obtains a resonance judgment key value. Subsequently, the evaluation result of the voltage source converter grid-connected harmonic resonance only needs to be determined through the resonance judgment key value, and it can simply and effectively determine whether a VSC grid-connected system will have harmonic resonance.

Description

Technical Field

[0001] The invention relates to the technical field of data processing, and in particular to a voltage source converter grid-connected harmonic resonance evaluation and analysis method. Background Art

[0002] With the rapid development of new energy and power electronics technology, the traditional power system based on synchronous generators is accelerating its transformation to a new power system based on new energy. Voltage-Source Converters (VSC), as a widely used device in the grid connection of new energy equipment, have attracted the attention of R&D personnel.

[0003] Due to the extensive application of voltage source converters, voltage source converters have become one of the key factors of harmonic resonance in power systems. Voltage source converters have frequency coupling for multi-frequency harmonic responses, which changes the node harmonic admittance matrix form of the system, which is not conducive to the system planning and design of VSC grid connection and the safe operation evaluation. Therefore, a simple and effective systematic evaluation scheme is needed to determine whether harmonic resonance will occur in the VSC grid-connected system. Summary of the invention

[0004] The object of the present invention is to provide a voltage source converter grid-connected harmonic resonance evaluation and analysis method to simply and effectively determine whether a VSC grid-connected system will have harmonic resonance.

[0005] A voltage source converter grid-connected harmonic resonance evaluation and analysis method comprises the following steps;

[0006] Step S1, dividing the harmonic response closed-loop process of the voltage source converter into four processes, namely, the harmonic response process at the common interface, the harmonic response process of the control loop, the harmonic response process of the voltage source converter AC / DC side, and the harmonic response process of the front-end filter, and establishing a harmonic model considering the harmonic coupling effect according to the four processes, and obtaining the harmonic coupling admittance according to the harmonic model;

[0007] Step S2, according to the number of network nodes of the voltage source converter grid-connected system u and component parameters, with the highest low-order harmonics of concern m As the range, according to the node arrangement, the node injection current and node voltage are expanded according to the harmonic components to obtain r × r The harmonic admittance matrix of the network nodes is r =0.5× u ×( m -1);

[0008] Step S3, according to the harmonic coupling admittance obtained in step S1, the r × rThe harmonic admittance matrix of the order network node is transformed to obtain the frequency coupling effect. r × r Harmonic admittance matrix of order network nodes;

[0009] Step S4, the frequency coupling effect obtained in step S3 r × r Perform singular value decomposition on the harmonic admittance matrix of the first-order network node to obtain the minimum singular value, and use the minimum singular value as the key value for resonance judgment;

[0010] Step S5, determining the evaluation result of the grid-connected harmonic resonance of the voltage source converter according to the resonance judgment key value obtained in step S4.

[0011] According to the voltage source converter grid-connected harmonic resonance evaluation and analysis method provided by the present invention, the harmonic response closed-loop process of the voltage source converter is divided into four processes, and a harmonic model considering the harmonic coupling effect is established. Compared with the traditional VSC harmonic model, the present invention clarifies the internal harmonic coupling mechanism and coupling strength of the VSC in the form of analytical impedance, so that the expression of the VSC coupling effect is more intuitive. Then, the present invention obtains the harmonic coupling admittance according to the harmonic model, and then obtains the harmonic admittance matrix representing the frequency coupling effect. This process repeatedly considers the frequency coupling situation, and then applies the singular value decomposition (SVD) algorithm to perform data dimension reduction on the harmonic admittance matrix representing the frequency coupling effect, extracts the main features, and obtains the resonance judgment key value. Subsequently, the evaluation result of the voltage source converter grid-connected harmonic resonance only needs to be determined by the resonance judgment key value, which can simply and effectively determine whether the VSC grid-connected system will have harmonic resonance. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic flow chart of the voltage source converter grid-connected harmonic resonance evaluation and analysis method of the present invention. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 are within the scope of protection of the present invention.

[0014] See also Figure 1 The voltage source converter grid-connected harmonic resonance evaluation and analysis method provided by the embodiment of the present invention comprises steps S1 to S5:

[0015] Step S1, divide the harmonic response closed-loop process of the voltage source converter into four processes, namely, the harmonic response process at the common interface, the harmonic response process of the control loop, the harmonic response process of the voltage source converter AC / DC side, and the harmonic response process of the front-end filter. According to these four processes, a harmonic model considering the harmonic coupling effect is established, and the harmonic coupling admittance is obtained according to the harmonic model.

[0016] Among them, for the harmonic response process at the point of common coupling (PCC), the resonance evaluation of the system needs to set the background harmonic, so the voltage and current at the PCC (taking phase a as an example) satisfy the following expression:

[0017] ;

[0018] ;

[0019] in, V pa Indicates the a-phase voltage at the common interface, V p1 represents the amplitude of the fundamental frequency component of the voltage of phase a, V ph+ Indicates the amplitude of the positive sequence harmonic component of phase a voltage, V ph- Indicates the amplitude of the negative sequence harmonic component of phase a voltage, I pa represents the a-phase current, I p1 represents the amplitude of the fundamental frequency component of phase a current, I ph+ Indicates the amplitude of the positive sequence harmonic component of phase a current, I ph- Indicates the amplitude of the negative sequence harmonic component of phase a current, represents the angular frequency of the fundamental frequency component, represents the angular frequency of the positive sequence harmonic component, represents the angular frequency of the negative sequence harmonic component, represents the phase angle of the fundamental frequency voltage of phase a, It represents the phase angle of the positive sequence harmonic component of phase a voltage, It represents the phase angle of the negative sequence harmonic component of phase a voltage, represents the phase angle of the fundamental frequency component of phase a current, It represents the phase angle of the positive sequence harmonic component of phase a current, It represents the phase angle of negative sequence harmonic component of phase a current, t Indicates time.

[0020] The internal control of the voltage source converter is generally realized by dq variables, in which the zero-sequence harmonic component is zero, so the zero-sequence component is omitted, and the dq component of the current and voltage of phase a at the PCC satisfies the following expression:

[0021] ;

[0022] ;

[0023] in, V abc Indicates the abc three-phase voltage at the public interface, I abc Indicates the abc three-phase current at the public interface, V dq Represents the dq components of the abc three-phase voltage at the common interface, I dq Represents the dq components of the abc three-phase current at the common interface, T Represents the dq transformation matrix.

[0024] For the control loop harmonic response process, the control loop response process can be divided into an outer control loop, an inner control loop and a modulation signal. The outer control loop and the inner control loop are determined by the specific control scheme to output the current / voltage reference value. Since the sampled value of the input control loop has harmonic components after dq transformation, the control loop output also has harmonic components, which are sent to the modulation signal. The harmonic component in the a-phase modulation signal satisfies the following expression:

[0025] ;

[0026] in, m ah Indicates the harmonic components contained in the modulated signal. V nom-p represents the phase voltage amplitude of phase a, V dc0 represents the steady-state value of the DC side capacitor voltage of the voltage source converter, V ta_harmonic Indicates the harmonic components contained in the modulation signal input reference voltage;

[0027] For the harmonic response process of the AC / DC side of the voltage source converter, the harmonic current response of phase a on the AC side of the VSC is used as the intermediate variable for derivation and should satisfy the following expression:

[0028] ;

[0029] in, I caa represents the a-phase current on the AC side of the voltage source converter, I ca1 represents the amplitude of the fundamental frequency component of phase a current, represents the phase angle of the fundamental frequency component of phase a current, I cah+Indicates the amplitude of the positive sequence harmonic component of phase a current, It represents the phase angle of the positive sequence harmonic component of phase a current, I cah- Indicates the amplitude of the negative sequence harmonic component of phase a current, Indicates the phase angle of the negative-sequence harmonic component of phase a current.

[0030] The VSC DC side current can be calculated by the switching function and the AC side current. The VSC DC side current and harmonic voltage satisfy the following expressions:

[0031] ;

[0032] ;

[0033] in, I dc represents the DC side current of the voltage source converter, I dc0 represents the DC component of the DC side current of the voltage source converter, I dch represents the harmonic component of the DC side current of the voltage source converter, m a represents the a-phase modulation signal, m b represents the b-phase modulation signal, m c represents the c-phase modulation signal, I cab represents the b-phase current on the AC side of the voltage source converter, I cac represents the c-phase current on the AC side of the voltage source converter, V dc represents the DC side voltage of the voltage source converter, V dch represents the harmonic component of the DC side voltage of the voltage source converter, C dc represents the DC side capacitance, I dch represents the harmonic component of the DC side current of the voltage source converter, I dc0 Represents the DC component of the DC side current of the voltage source converter.

[0034] Furthermore, the harmonic current response of phase a on the AC side of the VSC satisfies the following expression:

[0035] ;

[0036] in, V cah represents the harmonic component of the voltage on the AC side of the voltage source converter, hIndicates taking harmonic components.

[0037] For the harmonic response process of the front-end filter, the harmonic response process of the front-end filter is obtained according to the harmonic voltage component on the AC side of the voltage source converter, the harmonic voltage component at the common interface, and the harmonic current component at the common interface. The harmonic response process of the front-end filter satisfies the following formula:

[0038] ;

[0039] in, Z L1 , Z L2 is the harmonic impedance of the LCL filter inductor, Z Cf is the harmonic impedance of the LCL filter capacitor, V pah Indicates the harmonic component of phase a voltage at the public interface, I pah Indicates the harmonic component of phase A current at the common interface.

[0040] The harmonic current on the VSC AC side is regarded as an intermediate variable, and other harmonic response closed-loop processes are combined to establish a VSC harmonic model. Specifically, the harmonic model considering the harmonic coupling effect established in the present invention satisfies the following conditional formula:

[0041] ;

[0042] in, V ps Indicates the phase voltage at the common interface s Subharmonic components, V pn Indicates the phase voltage at the common interface n Subharmonic components, I ps Indicates the current injected at the public interface s Subharmonic components, I pn Indicates the current injected at the public interface n Subharmonic components, Y s,s The voltage source converter s Harmonic admittance under subharmonic current excitation, Y s,n The voltage source converter n Harmonic admittance under subharmonic current excitation, Y n,s The voltage source converter s Subharmonic current excitation corresponds to n Harmonic coupling admittance of subharmonic voltage, Yn,n The voltage source converter n Subharmonic current excitation corresponds to s The harmonic coupling admittance of the subharmonic voltage, and s = n +2.

[0043] Step S2, according to the number of network nodes of the voltage source converter grid-connected system u and component parameters, with the highest low-order harmonics of concern m As the range, according to the node arrangement, the node injection current and node voltage are expanded according to the harmonic components to obtain r × r The harmonic admittance matrix of the network nodes is r =0.5× u ×( m -1).

[0044] Among them, in step S2, the even-order harmonic admittance is ignored, r × r Harmonic admittance matrix of network nodes Y is a symmetric matrix, Y Satisfy the following formula:

[0045] ;

[0046] in, Y 3,3 represents the harmonic self-admittance of each node under the third harmonic excitation, Y 5,5 represents the harmonic self-admittance of each node under the 5th harmonic excitation, Y 7,7 represents the harmonic self-admittance of each node under the 7th harmonic excitation, Y m,m express m Harmonic self-admittance of each node under subharmonic excitation, Y Subscript 1,1,2,2, u , u Respectively represent node 1, node 2, and node u The harmonic self-admittance of Y Subscript 1,2,1, u 、2,1、2, u , u ,3. u , 2 respectively represent the relationship between node 1 and node 2, node 1 and node u Between, between node 2 and node 1, between node 2 and node u Between nodes u and node 3, node u and the harmonic self-admittance between node 2.

[0047] It should be noted that the harmonic self-admittance of the VSC at the node at the PCC and the VSC harmonic admittance part of the mutual admittance between the PCC and other nodes can be calculated according to the harmonic model obtained in step S2.

[0048] Step S3, according to the harmonic coupling admittance obtained in step S1, the r × r The harmonic admittance matrix of the order network node is transformed to obtain the frequency coupling effect. r × r Harmonic admittance matrix of network nodes of order .

[0049] Among them, for the network nodes corresponding to PCC, the frequency coupling response of VSC to harmonics causes the admittance of the network nodes to change. Therefore, for the nodes with harmonic frequency coupling, the content of the matrix is ​​modified to obtain the frequency coupling effect. r × r Harmonic admittance matrix of network nodes Y 1.

[0050] Assuming that node 1 is a PCC node, except for the harmonic self-admittance matrix of the PCC node, the remaining harmonic self-admittance matrices and harmonic mutual-admittance matrices are the same as Y Since the frequency coupling occurs between harmonics with an order tolerance of 2, r × r The first harmonic self-admittance small matrix in the harmonic admittance matrix of the first-order network node, the matrix elements of the i-th row, j-th column and the i-th column, j-th row should be the harmonic coupling admittance of the VSC. i and j are integers and satisfy the following expression:

[0051] j=i+1;

[0052] .

[0053] Specifically, the frequency coupling effect r × r Harmonic admittance matrix of network nodes Y 1 satisfies the following formula:

[0054] ;

[0055] in, Y 3,5 It represents the harmonic coupling admittance corresponding to the 5th harmonic voltage under the 3rd harmonic current excitation, Y 5,3 It represents the harmonic coupling admittance corresponding to the 3rd harmonic voltage under the 5th harmonic current excitation, Y 5,7 It represents the harmonic coupling admittance corresponding to the 7th harmonic voltage under the 5th harmonic current excitation, Y7,5 It represents the harmonic coupling admittance of the 5th harmonic voltage under the 7th harmonic current excitation, Y m-2,m-2 express m - Harmonic self-admittance of each node under 2nd harmonic excitation, Y m-2,m express m -2nd harmonic current excitation m Harmonic coupling admittance of subharmonic voltage, Y m,m-2 express m Subharmonic current excitation corresponds to m -Harmonic coupling admittance of the 2nd harmonic voltage.

[0056] Step S4, the frequency coupling effect obtained in step S3 r × r The harmonic admittance matrix of the network node is decomposed into singular values ​​to obtain the minimum singular value, which is used as the key value for resonance judgment.

[0057] Wherein, under the premise of retaining the original data information, SVD is applied to the frequency coupling effect obtained in step S3. r × r The harmonic admittance matrix of the network node is subjected to dimension reduction and feature extraction by singular value decomposition to find out the hidden mode and obtain the minimum singular value, which is the key value for resonance judgment.

[0058] In step S4, the following condition is satisfied:

[0059] ;

[0060] ;

[0061] ;

[0062] in, O , K for A unitary matrix of order , E for A diagonal matrix of order , express E The matrix element in the first column and first row of express E The matrix element in the second column and the second row of express E The matrix element in the 3rd column and the 3rd row of express E The matrix element in the 4th column and the 4th row of express E Ther Column, No. r The matrix elements of the rows, Represents the smallest singular value.

[0063] in, , , , , …, are all singular values, that is Y 1's implicit mode, take , , , , …, The minimum value among them is taken as the key value for resonance judgment.

[0064] Step S5, determining the evaluation result of the grid-connected harmonic resonance of the voltage source converter according to the resonance judgment key value obtained in step S4.

[0065] Specifically, the threshold is also preset, and if the resonance judgment key value obtained in step S4 is less than the threshold, it is determined that the voltage source converter grid-connected harmonic resonance has occurred.

[0066] In summary, according to the voltage source converter grid-connected harmonic resonance evaluation and analysis method provided by the present invention, the harmonic response closed-loop process of the voltage source converter is divided into four processes, and a harmonic model considering the harmonic coupling effect is established. Compared with the traditional VSC harmonic model, the present invention clarifies the internal harmonic coupling mechanism and coupling strength of the VSC in the form of analytical impedance, so that the expression of the VSC coupling effect is more intuitive. Then, the present invention obtains the harmonic coupling admittance according to the harmonic model, and then obtains the harmonic admittance matrix representing the frequency coupling effect. This process repeatedly considers the frequency coupling situation, and then applies the singular value decomposition (SVD) algorithm to perform data dimension reduction on the harmonic admittance matrix representing the frequency coupling effect, extracts the main features, and obtains the resonance judgment key value. Subsequently, the evaluation result of the voltage source converter grid-connected harmonic resonance only needs to be determined by the resonance judgment key value, which can simply and effectively determine whether harmonic resonance will occur in the VSC grid-connected system.

[0067] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0068] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for evaluating and analyzing harmonic resonance of a voltage source converter connected to the grid, characterized in that: The steps include: Step S1, dividing the harmonic response closed-loop process of the voltage source converter into four processes, namely, the harmonic response process at the common interface, the harmonic response process of the control loop, the harmonic response process of the voltage source converter AC / DC side, and the harmonic response process of the front-end filter, and establishing a harmonic model considering the harmonic coupling effect according to the four processes, and obtaining the harmonic coupling admittance according to the harmonic model; Step S2, according to the number of network nodes of the voltage source converter grid-connected system u and component parameters, with the highest low-order harmonics of concern m As the range, according to the node arrangement, the node injection current and node voltage are expanded according to the harmonic components to obtain r × r The harmonic admittance matrix of the network nodes is r =0.5× u ×( m -1); Step S3, according to the harmonic coupling admittance obtained in step S1, the r × r The harmonic admittance matrix of the order network node is transformed to obtain the frequency coupling effect. r × r Harmonic admittance matrix of order network nodes; Step S4, the frequency coupling effect obtained in step S3 r × r Perform singular value decomposition on the harmonic admittance matrix of the first-order network node to obtain the minimum singular value, and use the minimum singular value as the key value for resonance judgment; Step S5, determining the evaluation result of the grid-connected harmonic resonance of the voltage source converter according to the resonance judgment key value obtained in step S4.

2. The voltage source converter grid-connected harmonic resonance evaluation and analysis method according to claim 1, characterized in that: In step S1, the harmonic response process at the public interface satisfies the following formula: ； ； in, V pa Indicates the a-phase voltage at the common interface, V p1 Indicates the amplitude of the fundamental frequency component of the voltage of phase a, V ph+ Indicates the amplitude of the positive sequence harmonic component of phase a voltage, V ph- Indicates the amplitude of the negative sequence harmonic component of phase a voltage, I pa represents the a-phase current, I p1 represents the amplitude of the fundamental frequency component of phase a current, I ph+ Indicates the amplitude of the positive sequence harmonic component of phase a current, I ph- Indicates the amplitude of the negative sequence harmonic component of phase a current, represents the angular frequency of the fundamental frequency component, represents the angular frequency of the positive sequence harmonic component, represents the angular frequency of the negative sequence harmonic component, represents the phase angle of the fundamental frequency voltage of phase a, It represents the phase angle of the positive sequence harmonic component of phase a voltage, It represents the phase angle of negative sequence harmonic component of phase a voltage, represents the phase angle of the fundamental frequency component of phase a current, It represents the phase angle of the positive sequence harmonic component of phase a current, It represents the phase angle of negative sequence harmonic component of phase a current, t Indicates time; The control loop harmonic response process satisfies the following formula: ； in, m ah Indicates the harmonic components contained in the modulated signal. V nom-p represents the phase voltage amplitude of phase a, V dc0 represents the steady-state value of the DC side capacitor voltage of the voltage source converter, V ta_harmonic Indicates the harmonic components contained in the modulation signal input reference voltage; The AC / DC side harmonic response process of the voltage source converter satisfies the following equation: ； ； in, V cah represents the harmonic component of the voltage on the AC side of the voltage source converter, m a represents the a-phase modulation signal, V dc represents the DC side voltage of the voltage source converter, h Indicates taking the harmonic component, V dch represents the harmonic component of the DC side voltage of the voltage source converter, C dc represents the DC side capacitance, I dch represents the harmonic component of the DC side current of the voltage source converter, I dc0 represents the DC component of the DC side current of the voltage source converter; For the harmonic response process of the front-end filter, the harmonic response process of the front-end filter is obtained according to the harmonic voltage component on the AC side of the voltage source converter, the harmonic voltage component at the common interface, and the harmonic current component at the common interface. The harmonic response process of the front-end filter satisfies the following formula: ； in, Z L1 , Z L2 is the harmonic impedance of the LCL filter inductor, Z Cf is the harmonic impedance of the LCL filter capacitor, V pah Indicates the harmonic component of phase a voltage at the public interface, I pah Indicates the harmonic component of phase A current at the common interface.

3. The voltage source converter grid-connected harmonic resonance evaluation and analysis method according to claim 2, characterized in that: The harmonic model considering the harmonic coupling effect satisfies the following conditional formula: ； in, V ps Indicates the phase voltage at the common interface s Subharmonic components, V pn Indicates the phase voltage at the common interface n Subharmonic components, I ps Indicates the current injected at the public interface s Subharmonic components, I pn Indicates the current injected at the public interface n Subharmonic components, Y s,s The voltage source converter s Harmonic admittance under subharmonic current excitation, Y n,n The voltage source converter n Harmonic admittance under subharmonic current excitation, Y s,n The voltage source converter s Subharmonic current excitation corresponds to n Harmonic coupling admittance of subharmonic voltage, Y n,s The voltage source converter n Subharmonic current excitation corresponds to s The harmonic coupling admittance of the subharmonic voltage, and s = n +2.

4. The voltage source converter grid-connected harmonic resonance evaluation and analysis method according to claim 3, characterized in that: In step S2, r × r Harmonic admittance matrix of network nodes Y Satisfy the following formula: ； in, Y 3,3 represents the harmonic self-admittance of each node under the third harmonic excitation, Y 5,5 represents the harmonic self-admittance of each node under the 5th harmonic excitation, Y 7,7 represents the harmonic self-admittance of each node under the 7th harmonic excitation, Y m,m express m Harmonic self-admittance of each node under subharmonic excitation, Y Subscript 1,1,2,2, u , u Respectively represent node 1, node 2, and node u The harmonic self-admittance of Y Subscript 1,2,1, u 、2,1、2, u , u ,3. u , 2 respectively represent the relationship between node 1 and node 2, node 1 and node u Between, between node 2 and node 1, between node 2 and node u Between nodes u and node 3, node u and the harmonic self-admittance between node 2.

5. The voltage source converter grid-connected harmonic resonance evaluation and analysis method according to claim 4, characterized in that: In step S3, the frequency coupling effect is represented by r × r Harmonic admittance matrix of network nodes Y 1 satisfies the following formula: ； in, Y 3,5 It represents the harmonic coupling admittance corresponding to the 5th harmonic voltage under the 3rd harmonic current excitation, Y 5,3 It represents the harmonic coupling admittance corresponding to the 3rd harmonic voltage under the 5th harmonic current excitation, Y 5,7 It represents the harmonic coupling admittance corresponding to the 7th harmonic voltage under the 5th harmonic current excitation, Y 7,5 It represents the harmonic coupling admittance of the 5th harmonic voltage under the 7th harmonic current excitation, Y m-2,m-2 express m - Harmonic self-admittance of each node under 2nd harmonic excitation, Y m-2,m express m -2nd harmonic current excitation m Harmonic coupling admittance of subharmonic voltage, Y m,m-2 express m Subharmonic current excitation corresponds to m -Harmonic coupling admittance of the 2nd harmonic voltage.

6. The voltage source converter grid-connected harmonic resonance evaluation and analysis method according to claim 5, characterized in that: In step S4, the following condition is satisfied: ； ； ； in, O , K for A unitary matrix of order , E for A diagonal matrix of order , express E The matrix element in the first column and first row of express E The matrix element in the second column and the second row of express E The matrix element in the 3rd column and the 3rd row of express E The matrix element in the 4th column and the 4th row of express E The r Column, No. r The matrix elements of the rows, Represents the smallest singular value.

7. The voltage source converter grid-connected harmonic resonance evaluation and analysis method according to claim 1, characterized in that: Step S5 specifically includes: If the resonance judgment key value obtained in step S4 is less than the threshold value, it is determined that the voltage source converter grid-connected harmonic resonance has occurred.

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