Oscillation risk analysis method and device of inverter

Abstract

The invention relates to the technical field of new energy power generation, and particularly provides an inverter oscillation risk analysis method and device, and the method comprises the steps: injecting a harmonic voltage at a port side of an inverter, and calculating an admittance matrix of the inverter; determining a transfer function from harmonic voltage to terminal voltage harmonic and current harmonic in a power grid based on the admittance matrix of the inverter; and carrying out oscillation risk analysis on the inverter based on a Bode diagram corresponding to the transfer function from the harmonic voltage in the power grid to the terminal voltage harmonic and the current harmonic. According to the technical scheme provided by the invention, the harmonic characteristics of different frequencies can be analyzed, and the frequency band with the oscillation risk of the voltage and the current can be accurately judged.

Description

Technical Field

[0001] The present invention relates to the technical field of renewable energy power generation, and in particular to an oscillation risk analysis method and device for an inverter. Background Art

[0002] At present, new energy represented by wind power and photovoltaic power is experiencing rapid development opportunities. A large number of new energy power stations are connected to the large power grid through 3-4 level transformer step-up. The transformer and line impedance increase the electrical distance between the new energy power station and the large power grid, and reduce the electrical connection with the large power grid. At the new energy inverter end, the grid strength at the grid connection point is weak and lacks voltage support. Due to the frequent occurrence of various stability problems such as broadband oscillation and overvoltage under weak power grids, it has attracted widespread attention from researchers.

[0003] Inverters are power electronic devices that can convert DC power into AC power by pulse width modulation technology. A large number of high-frequency harmonics will be generated during the inversion process. Inverter standards usually require that the total harmonic distortion (THD) of the inverter output current be less than 5%. To this end, by setting a higher switching frequency and configuring filters, the harmonic content of the inverter can usually be controlled within a smaller range in a strong power grid. However, as the strength of the power grid weakens, the stability margin of the inverter decreases, and harmonics are easily generated, which manifests as oscillations. There have been many broadband oscillation accidents, with oscillation and harmonic frequencies ranging from a few Hz to thousands of Hz. Harmonics may cause overvoltage and overcurrent faults, resulting in the inverter being unable to operate stably, posing risks to the safe and stable operation of the power grid. Therefore, in order to improve the stability of new energy after it is connected to a weak power grid, it is very necessary to study the harmonic characteristics of the inverter under a weak power grid.

[0004] In the Chinese invention patent (application number 202211080560.3), whether the output current will be amplified is determined based on whether the Nyquist curve of the grid impedance and the inverter impedance enters the harmonic amplification region. However, this method can only be used to compare whether the current harmonics of weak grids are amplified or reduced, and the specific calculation method and expression of harmonic current and voltage are not given. Summary of the invention

[0005] In order to overcome the above-mentioned defects, the present invention proposes an oscillation risk analysis method and device for an inverter.

[0006] In a first aspect, an oscillation risk analysis method for an inverter is provided, the oscillation risk analysis method for an inverter comprising:

[0007] Inject harmonic voltage on the inverter port side and calculate the inverter's admittance matrix;

[0008] Determine the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter;

[0009] The oscillation risk analysis of the inverter is performed based on the Bode diagram corresponding to the transfer function from the harmonic voltage in the power grid to the voltage harmonics and current harmonics at the machine end.

[0010] Preferably, injecting harmonic voltage at the inverter port side and calculating the admittance matrix of the inverter includes:

[0011] Inject positive-sequence harmonic voltage at the inverter port side, and calculate the positive-sequence admittance Y of the inverter's admittance matrix as follows: 11 and positive and negative sequence coupling admittance Y 21 :

[0012]

[0013] Inject negative sequence harmonic voltage on the inverter port side and calculate the negative sequence admittance Y of the inverter as follows: 22 and negative positive sequence coupling admittance Y 12 :

[0014]

[0015] In the above formula, I p is the positive sequence harmonic current, U p is the positive sequence harmonic voltage, I n is the negative sequence harmonic current, U n It is the negative sequence harmonic voltage.

[0016] Furthermore, the frequency f of the positive sequence harmonic voltage injected into the inverter port side is p The frequency f of the negative sequence harmonic voltage injected at the inverter port side n Satisfy: f n =f p -2f1, where f1 is the rated frequency of the power grid.

[0017] Furthermore, the transfer function of determining the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes:

[0018] Determine the transfer function from the positive sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula:

[0019]

[0020] In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, is the transfer function from the positive sequence harmonic voltage in the power grid to the negative sequence harmonic voltage at the generator end, L sis the grid inductance, s is a complex variable, ω1 is the rated angular frequency of the grid, and j is an imaginary unit.

[0021] Furthermore, the rated angular frequency of the power grid is as follows:

[0022] ω1=2πf1

[0023] In the above formula, f1 is the rated frequency of the power grid.

[0024] Furthermore, the transfer function of determining the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes:

[0025] Determine the transfer function from the positive sequence harmonic voltage in the power grid to the machine-end current harmonics as follows:

[0026]

[0027] In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the generator end, It is the transfer function from the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end.

[0028] Furthermore, the transfer function of determining the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes:

[0029] Determine the transfer function from the negative sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula:

[0030]

[0031] In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end.

[0032] Furthermore, the transfer function of determining the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes:

[0033] Determine the transfer function from the negative sequence harmonic voltage in the power grid to the machine-end current harmonics as follows:

[0034]

[0035] In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end.

[0036] Further, the oscillation risk analysis of the inverter based on the Bode diagram corresponding to the transfer function from the harmonic voltage in the power grid to the machine-end voltage harmonics and current harmonics includes:

[0037] When there is a peak in the Bode diagram corresponding to the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, or the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the frequency band corresponding to the peak is regarded as a frequency band with oscillation risk.

[0038] In a second aspect, an oscillation risk analysis device for an inverter is provided, the oscillation risk analysis device for the inverter comprising:

[0039] A calculation module, used for injecting harmonic voltage at the port side of the inverter and calculating the admittance matrix of the inverter;

[0040] A determination module, used to determine the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter;

[0041] The analysis module is used to perform oscillation risk analysis on the inverter based on the Bode diagram corresponding to the transfer function from the harmonic voltage in the power grid to the machine-end voltage harmonics and current harmonics.

[0042] Preferably, the calculation module is specifically used for:

[0043] Inject positive-sequence harmonic voltage at the inverter port side, and calculate the positive-sequence admittance Y of the inverter's admittance matrix as follows: 11 and positive and negative sequence coupling admittance Y 21 :

[0044]

[0045] Inject negative sequence harmonic voltage at the inverter port side and calculate the negative sequence admittance Y of the inverter as follows: 22 and negative positive sequence coupling admittance Y 12 :

[0046]

[0047] In the above formula, I p is the positive sequence harmonic current, U p is the positive sequence harmonic voltage, In is the negative sequence harmonic current, U n It is the negative sequence harmonic voltage.

[0048] Furthermore, the frequency f of the positive sequence harmonic voltage injected into the inverter port side is p The frequency f of the negative sequence harmonic voltage injected at the inverter port side n Satisfy: f n =f p -2f1, where f1 is the rated frequency of the power grid.

[0049] Furthermore, the determination module is specifically used for:

[0050] Determine the transfer function from the positive sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula:

[0051]

[0052] In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, is the transfer function from the positive sequence harmonic voltage in the power grid to the negative sequence harmonic voltage at the generator end, L s is the grid inductance, s is a complex variable, ω1 is the rated angular frequency of the grid, and j is an imaginary unit.

[0053] Furthermore, the rated angular frequency of the power grid is as follows:

[0054] ω1=2πf1

[0055] In the above formula, f1 is the rated frequency of the power grid.

[0056] Furthermore, the determination module is specifically used for:

[0057] Determine the transfer function from the positive sequence harmonic voltage in the power grid to the machine-end current harmonics as follows:

[0058]

[0059] In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the generator end, It is the transfer function from the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end.

[0060] Furthermore, the determination module is specifically used for:

[0061] Determine the transfer function from the negative sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula:

[0062]

[0063] In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end.

[0064] Furthermore, the determination module is specifically used for:

[0065] Determine the transfer function from the negative sequence harmonic voltage in the power grid to the machine-end current harmonics as follows:

[0066]

[0067] In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end.

[0068] Furthermore, the analysis module is specifically used for:

[0069] When there is a peak in the Bode diagram corresponding to the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, or the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the frequency band corresponding to the peak is regarded as a frequency band with oscillation risk.

[0070] In a third aspect, a computer device is provided, comprising: one or more processors;

[0071] The processor is configured to execute one or more programs;

[0072] When the one or more programs are executed by the one or more processors, the inverter oscillation risk analysis method is implemented.

[0073] In a fourth aspect, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed, the oscillation risk analysis method of the inverter is implemented.

[0074] The above one or more technical solutions of the present invention have at least one or more of the following beneficial effects:

[0075] The present invention provides an oscillation risk analysis method and device for an inverter, comprising: injecting harmonic voltage at the inverter port side and calculating the inverter's admittance matrix; determining the transfer function of the harmonic voltage in the power grid to the machine-end voltage harmonics and current harmonics based on the inverter's admittance matrix; and performing oscillation risk analysis on the inverter based on the Bode diagram corresponding to the transfer function of the harmonic voltage in the power grid to the machine-end voltage harmonics and current harmonics. The technical solution provided by the present invention can analyze the harmonic characteristics of different frequencies and accurately determine the frequency bands where the voltage and current have oscillation risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 1 is a flow chart of main steps of an oscillation risk analysis method for an inverter according to an embodiment of the present invention;

[0077] Figure 2 is the grid-side positive-sequence harmonic voltage U of the inverter according to the embodiment of the present invention. sp Positive sequence harmonic voltage U at the machine end p Bode plot of

[0078] Figure 3 is the grid-side positive-sequence harmonic voltage U of the inverter according to the embodiment of the present invention. sp Negative sequence harmonic voltage U at the machine end n Bode plot of

[0079] Figure 4 is the grid-side positive-sequence harmonic voltage U of the inverter according to the embodiment of the present invention. sp Positive sequence harmonic current I p Bode plot of

[0080] Figure 5 is the grid-side positive-sequence harmonic voltage U of the inverter according to the embodiment of the present invention. sp Negative sequence harmonic current I n Bode plot of

[0081] Figure 6 is the grid-side negative sequence harmonic voltage U of the inverter according to the embodiment of the present invention. sn Negative sequence harmonic voltage U at the machine end n Bode plot of

[0082] Figure 7 is the grid-side negative sequence harmonic voltage U of the inverter according to the embodiment of the present invention. sn Positive sequence harmonic voltage U at the machine end p Bode plot of

[0083] Figure 8 is the grid-side negative sequence harmonic voltage U of the inverter according to the embodiment of the present invention. sn Negative sequence harmonic current I n Bode plot of

[0084] Fig. 9 is the grid-side negative sequence harmonic voltage U of the inverter according to the embodiment of the present invention. sn Positive sequence harmonic current I p Bode plot of . DETAILED DESCRIPTION

[0085] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0086] 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.

[0087] As disclosed in the background technology, at present, new energy represented by wind power and photovoltaic power is experiencing rapid development opportunities. A large number of new energy power stations are connected to the large power grid by means of 3-4 level transformer step-up. The transformer and line impedance increase the electrical distance between the new energy power station and the large power grid, and reduce the electrical connection with the large power grid. At the new energy inverter end, the grid strength of the grid connection point is weak and lacks voltage support. Due to the frequent occurrence of various stability problems such as broadband oscillation and overvoltage under weak power grid, it has attracted widespread attention from researchers.

[0088] Inverters are power electronic devices that can convert DC power into AC power by pulse width modulation technology. A large number of high-frequency harmonics will be generated during the inversion process. Inverter standards usually require that the total harmonic distortion (THD) of the inverter output current be less than 5%. To this end, by setting a higher switching frequency and configuring filters, the harmonic content of the inverter can usually be controlled within a smaller range in a strong power grid. However, as the strength of the power grid weakens, the stability margin of the inverter decreases, and harmonics are easily generated, which manifests as oscillations. There have been many broadband oscillation accidents, with oscillation and harmonic frequencies ranging from a few Hz to thousands of Hz. Harmonics may cause overvoltage and overcurrent faults, resulting in the inverter being unable to operate stably, posing risks to the safe and stable operation of the power grid. Therefore, in order to improve the stability of new energy after it is connected to a weak power grid, it is very necessary to study the harmonic characteristics of the inverter under a weak power grid.

[0089] In the Chinese invention patent (application number 202211080560.3), whether the output current will be amplified is determined based on whether the Nyquist curve of the grid impedance and the inverter impedance enters the harmonic amplification region. However, this method can only be used to compare whether the current harmonics of weak grids are amplified or reduced, and the specific calculation method and expression of harmonic current and voltage are not given.

[0090] In order to improve the above problems, the present invention provides an oscillation risk analysis method and device for an inverter, including: injecting harmonic voltage on the inverter port side and calculating the inverter's admittance matrix; determining the transfer function of the harmonic voltage in the power grid to the machine-end voltage harmonics and current harmonics based on the inverter's admittance matrix; and performing oscillation risk analysis on the inverter based on the Bode diagram corresponding to the transfer function of the harmonic voltage in the power grid to the machine-end voltage harmonics and current harmonics. The technical solution provided by the present invention can analyze the harmonic characteristics of different frequencies and accurately determine the frequency bands where the voltage and current have oscillation risks. The above solution is described in detail below.

[0091] Example 1

[0092] See attached Figure 1 , Figure 1 FIG. 1 is a flow chart showing the main steps of an inverter oscillation risk analysis method according to an embodiment of the present invention. Figure 1 As shown, the oscillation risk analysis method of the inverter in the embodiment of the present invention mainly includes the following steps:

[0093] Step S101: injecting harmonic voltage at the inverter port side and calculating the inverter's admittance matrix;

[0094] Step S102: determining a transfer function from harmonic voltage in the power grid to terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter;

[0095] Step S103: performing an oscillation risk analysis on the inverter based on a Bode diagram corresponding to a transfer function from harmonic voltage in the power grid to voltage harmonics and current harmonics at the machine end.

[0096] In this embodiment, injecting harmonic voltage at the inverter port side and calculating the admittance matrix of the inverter includes:

[0097] Inject positive-sequence harmonic voltage at the inverter port side, and calculate the positive-sequence admittance Y of the inverter's admittance matrix as follows: 11 and positive and negative sequence coupling admittance Y 21 :

[0098]

[0099] Inject negative sequence harmonic voltage at the inverter port side and calculate the negative sequence admittance Y of the inverter as follows:22 and negative positive sequence coupling admittance Y 12 :

[0100]

[0101] In the above formula, I p is the positive sequence harmonic current, U p is the positive sequence harmonic voltage, I n is the negative sequence harmonic current, U n It is the negative sequence harmonic voltage.

[0102] In one embodiment, the frequency f of the positive sequence harmonic voltage injected at the inverter port side is p The frequency f of the negative sequence harmonic voltage injected at the inverter port side n Satisfy: f n =f p -2f1, where f1 is the rated frequency of the power grid.

[0103] In one embodiment, the determining of the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes:

[0104] Determine the transfer function from the positive sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula:

[0105]

[0106] In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, is the transfer function from the positive sequence harmonic voltage in the power grid to the negative sequence harmonic voltage at the generator end, L s is the grid inductance, s is a complex variable, ω1 is the rated angular frequency of the grid, and j is an imaginary unit.

[0107] In one embodiment, the rated angular frequency of the power grid is as follows:

[0108] ω1=2πf1

[0109] In the above formula, f1 is the rated frequency of the power grid.

[0110] In one embodiment, the determining of the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes:

[0111] Determine the transfer function from the positive sequence harmonic voltage in the power grid to the machine-end current harmonics as follows:

[0112]

[0113] In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the generator end, It is the transfer function from the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end.

[0114] In one embodiment, the determining of the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes:

[0115] Determine the transfer function from the negative sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula:

[0116]

[0117] In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end.

[0118] In one embodiment, the determining of the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes:

[0119] Determine the transfer function from the negative sequence harmonic voltage in the power grid to the machine-end current harmonics as follows:

[0120]

[0121] In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end.

[0122] In one embodiment, the oscillation risk analysis of the inverter based on the Bode diagram corresponding to the transfer function from the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics includes:

[0123] When there is a peak in the Bode diagram corresponding to the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, or the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the frequency band corresponding to the peak is regarded as a frequency band with oscillation risk.

[0124] In a specific implementation, a Bode diagram of the transfer function from the positive sequence harmonic voltage at the grid side to the harmonic voltage and current at the machine end is drawn, and a frequency band with a higher amplitude is a frequency band with a greater risk of oscillation.

[0125] Figure 2 is the positive sequence harmonic voltage U on the grid side in the embodiment sp Positive sequence harmonic voltage U at the machine end p From the amplitude curve of the Bode plot, it can be seen that the amplitude at the inverter end is the highest in the 70-100Hz frequency band, indicating that positive sequence voltage harmonics are easily generated near the 70-100Hz frequency band, and the oscillation risk in this frequency band is relatively high.

[0126] Figure 3 is the positive sequence harmonic voltage U on the grid side in the embodiment sp Negative sequence harmonic voltage U at the machine end n From the amplitude curve of the Bode plot, it can be seen that there is no peak on the curve, and the risk of generating negative sequence voltage harmonics at the inverter end is small.

[0127] Figure 4 is the positive sequence harmonic voltage U on the grid side in the embodiment sp Positive sequence harmonic current I p From the amplitude curve of the Bode plot, it can be seen that the amplitude at the inverter end is the highest in the 10-30Hz and 60-90Hz frequency bands, indicating that positive sequence current harmonics are easily generated near the 10-30Hz and 60-90Hz frequency bands, and the oscillation risk in this frequency band is relatively high.

[0128] Figure 5 is the positive sequence harmonic voltage U on the grid side in the embodiment sp Negative sequence harmonic current I n From the amplitude curve of the Bode plot, it can be seen that the amplitude at the inverter end is the highest in the 10-40Hz and 60-90Hz frequency bands, indicating that negative sequence current harmonics are easily generated near the 10-40Hz and 60-90Hz frequency bands, and the oscillation risk in this frequency band is relatively high.

[0129] comprehensive Figure 2 to Figure 5 The analysis results show that when there are positive sequence harmonic voltages in the 10-40Hz and 60-100Hz frequency bands in the power grid, the risk of voltage and current oscillation on the inverter side is relatively high.

[0130] The Bode diagram of the transfer function from the negative-sequence harmonic voltage on the grid side to the harmonic voltage and current on the machine side is drawn. The frequency band with higher amplitude is the frequency band with greater risk of oscillation.

[0131] Figure 6 is the negative sequence harmonic voltage U on the grid side in the embodiment sn Negative sequence harmonic voltage U at the machine end nFrom the amplitude curve of the Bode plot, it can be seen that there is no peak on the curve, and the risk of generating negative sequence voltage harmonics at the inverter end is small.

[0132] Figure 7 is the negative sequence harmonic voltage U on the grid side in the embodiment sn Positive sequence harmonic voltage U at the machine end p From the amplitude curve of the Bode plot, it can be seen that there is no peak on the curve, and the risk of generating positive sequence voltage harmonics at the inverter end is small.

[0133] Figure 8 is the negative sequence harmonic voltage U on the grid side in the embodiment sn Negative sequence harmonic current I n From the amplitude curve of the Bode plot, it can be seen that there is no peak on the curve, and the risk of generating negative sequence current harmonics at the inverter end is small.

[0134] Fig. 9 is the negative sequence harmonic voltage U on the grid side in the embodiment sn Positive sequence harmonic current I p From the amplitude curve of the Bode plot, it can be seen that there is no peak on the curve, and the risk of generating positive sequence current harmonics at the inverter end is small.

[0135] comprehensive Figure 6 to Figure 9 The analysis results show that when there is a negative sequence harmonic voltage in the grid, the risk of voltage and current oscillation on the inverter side is small.

[0136] Example 2

[0137] Based on the same inventive concept, the present invention further provides an oscillation risk analysis device for an inverter, the oscillation risk analysis device for an inverter comprising:

[0138] A calculation module, used for injecting harmonic voltage at the port side of the inverter and calculating the admittance matrix of the inverter;

[0139] A determination module, used to determine the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter;

[0140] The analysis module is used to perform oscillation risk analysis on the inverter based on the Bode diagram corresponding to the transfer function from the harmonic voltage in the power grid to the machine-end voltage harmonics and current harmonics.

[0141] Preferably, the calculation module is specifically used for:

[0142] Inject positive-sequence harmonic voltage at the inverter port side, and calculate the positive-sequence admittance Y of the inverter's admittance matrix as follows: 11 and positive and negative sequence coupling admittance Y 21 :

[0143]

[0144] Inject negative sequence harmonic voltage at the inverter port side and calculate the negative sequence admittance Y of the inverter as follows: 22 and negative positive sequence coupling admittance Y 12 :

[0145]

[0146] In the above formula, I p is the positive sequence harmonic current, U p is the positive sequence harmonic voltage, I n is the negative sequence harmonic current, U n It is the negative sequence harmonic voltage.

[0147] Furthermore, the frequency f of the positive sequence harmonic voltage injected into the inverter port side is p The frequency f of the negative sequence harmonic voltage injected at the inverter port side n Satisfy: f n =f p -2f1, where f1 is the rated frequency of the power grid.

[0148] Furthermore, the determination module is specifically used for:

[0149] Determine the transfer function from the positive sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula:

[0150]

[0151] In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, is the transfer function from the positive sequence harmonic voltage in the power grid to the negative sequence harmonic voltage at the generator end, L s is the grid inductance, s is a complex variable, ω1 is the rated angular frequency of the grid, and j is an imaginary unit.

[0152] Furthermore, the rated angular frequency of the power grid is as follows:

[0153] ω1=2πf1

[0154] In the above formula, f1 is the rated frequency of the power grid.

[0155] Furthermore, the determination module is specifically used for:

[0156] Determine the transfer function from the positive sequence harmonic voltage in the power grid to the machine-end current harmonics as follows:

[0157]

[0158] In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the generator end, It is the transfer function from the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end.

[0159] Furthermore, the determination module is specifically used for:

[0160] Determine the transfer function from the negative sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula:

[0161]

[0162] In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end.

[0163] Furthermore, the determination module is specifically used for:

[0164] Determine the transfer function from the negative sequence harmonic voltage in the power grid to the machine-end current harmonics as follows:

[0165]

[0166] In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end.

[0167] Furthermore, the analysis module is specifically used for:

[0168] When there is a peak in the Bode diagram corresponding to the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, or the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the frequency band corresponding to the peak is regarded as a frequency band with oscillation risk.

[0169] Example 3

[0170] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor 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 gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the oscillation risk analysis method of an inverter in the above embodiment.

[0171] Example 4

[0172] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of an oscillation risk analysis method for an inverter in the above embodiment.

[0173] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0174] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0175] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0176] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0177] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for analyzing oscillation risk of an inverter, characterized in that: The method comprises: Inject harmonic voltage on the inverter port side and calculate the inverter's admittance matrix; Determine the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter; The oscillation risk analysis of the inverter is performed based on the Bode diagram corresponding to the transfer function from the harmonic voltage in the power grid to the voltage harmonics and current harmonics at the machine end.

2. The method according to claim 1, characterized in that The step of injecting harmonic voltage at the inverter port side and calculating the inverter admittance matrix includes: Inject positive-sequence harmonic voltage at the inverter port side, and calculate the positive-sequence admittance Y of the inverter's admittance matrix as follows: 11 and positive and negative sequence coupling admittance Y 21 : Inject negative sequence harmonic voltage at the inverter port side and calculate the negative sequence admittance Y of the inverter as follows: 22 and negative positive sequence coupling admittance Y 12 : In the above formula, I p is the positive sequence harmonic current, U p is the positive sequence harmonic voltage, I n is the negative sequence harmonic current, U n It is the negative sequence harmonic voltage.

3. The method according to claim 2, characterized in that The frequency f of the positive sequence harmonic voltage injected at the inverter port side p The frequency f of the negative sequence harmonic voltage injected at the inverter port side n Satisfy: f n =f p -2f1, where f1 is the rated frequency of the power grid.

4. The method according to claim 2, characterized in that The step of determining the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes: Determine the transfer function from the positive sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula: In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, is the transfer function from the positive sequence harmonic voltage in the power grid to the negative sequence harmonic voltage at the generator end, L s is the grid inductance, s is a complex variable, ω1 is the rated angular frequency of the grid, and j is an imaginary unit.

5. The method according to claim 4, characterized in that The rated angular frequency of the power grid is as follows: ω1=2πf1 In the above formula, f1 is the rated frequency of the power grid.

6. The method according to claim 5, characterized in that The step of determining the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes: Determine the transfer function from the positive sequence harmonic voltage in the power grid to the machine-end current harmonics as follows: In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the generator end, It is the transfer function from the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end.

7. The method according to claim 6, characterized in that The step of determining the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes: Determine the transfer function from the negative sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula: In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end.

8. The method according to claim 7, characterized in that The step of determining the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter includes: Determine the transfer function from the negative sequence harmonic voltage in the power grid to the machine-end current harmonics as follows: In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end.

9. The method according to claim 8, characterized in that The oscillation risk analysis of the inverter based on the Bode diagram corresponding to the transfer function from the harmonic voltage in the power grid to the machine-end voltage harmonics and current harmonics includes: When there is a peak in the Bode diagram corresponding to the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, or the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the frequency band corresponding to the peak is regarded as a frequency band with oscillation risk.

10. An oscillation risk analysis device for an inverter, characterized in that: The device comprises: A calculation module, used for injecting harmonic voltage at the port side of the inverter and calculating the admittance matrix of the inverter; A determination module, used to determine the transfer function of the harmonic voltage in the power grid to the terminal voltage harmonics and current harmonics based on the admittance matrix of the inverter; The analysis module is used to perform oscillation risk analysis on the inverter based on the Bode diagram corresponding to the transfer function from the harmonic voltage in the power grid to the machine-end voltage harmonics and current harmonics.

11. The device according to claim 10, characterized in that The calculation module is specifically used for: Inject positive-sequence harmonic voltage at the inverter port side, and calculate the positive-sequence admittance Y of the inverter's admittance matrix as follows: 11 and positive and negative sequence coupling admittance Y 21 : Inject negative sequence harmonic voltage at the inverter port side and calculate the negative sequence admittance Y of the inverter as follows: 22 and negative positive sequence coupling admittance Y 12 : In the above formula, I p is the positive sequence harmonic current, U p is the positive sequence harmonic voltage, I n is the negative sequence harmonic current, U n It is the negative sequence harmonic voltage.

12. The device according to claim 11, characterized in that The frequency f of the positive sequence harmonic voltage injected at the inverter port side p The frequency f of the negative sequence harmonic voltage injected at the inverter port side n Satisfy: f n =f p -2f1, where f1 is the rated frequency of the power grid.

13. The device according to claim 11, characterized in that The determination module is specifically used for: Determine the transfer function from the positive sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula: In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, is the transfer function from the positive sequence harmonic voltage in the power grid to the negative sequence harmonic voltage at the generator end, L s is the grid inductance, s is a complex variable, ω1 is the rated angular frequency of the grid, and j is an imaginary unit.

14. The device according to claim 13, characterized in that The rated angular frequency of the power grid is as follows: ω1=2πf1 In the above formula, f1 is the rated frequency of the power grid.

15. The device according to claim 14, characterized in that The determination module is specifically used for: Determine the transfer function from the positive sequence harmonic voltage in the power grid to the machine-end current harmonics as follows: In the above formula, is the transfer function from the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the generator end, It is the transfer function from the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end.

16. The device according to claim 15, characterized in that The determination module is specifically used for: Determine the transfer function from the negative sequence harmonic voltage in the power grid to the terminal voltage harmonic according to the following formula: In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the generator end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end.

17. The device according to claim 16, characterized in that The determination module is specifically used for: Determine the transfer function from the negative sequence harmonic voltage in the power grid to the machine-end current harmonics as follows: In the above formula, is the transfer function from the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, It is the transfer function from the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end.

18. The device according to claim 17, characterized in that The analysis module is specifically used for: When there is a peak in the Bode diagram corresponding to the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, the transfer function of the positive-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic voltage at the machine end, the transfer function of the negative-sequence harmonic voltage in the power grid to the positive-sequence harmonic current at the machine end, or the transfer function of the negative-sequence harmonic voltage in the power grid to the negative-sequence harmonic current at the machine end, the frequency band corresponding to the peak is regarded as a frequency band with oscillation risk.

19. A computer device, characterized in that: include: one or more processors; The processor is configured to execute one or more programs; When the one or more programs are executed by the one or more processors, the oscillation risk analysis method for the inverter according to any one of claims 1 to 9 is implemented.

20. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the oscillation risk analysis method of the inverter as claimed in any one of claims 1 to 9 is implemented.

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