A damping compensation method and device for a new energy grid-connected system based on an optimized control damper

Abstract

The present invention discloses a damping compensation method and device for a new energy grid-connected system based on an optimized control damper. The method includes: obtaining underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology; recording the frequency corresponding to the minimum real part of the eigenvalues as the first frequency; calculating the influence coefficient set of the damper at the first frequency; obtaining the damping deficiency of the grid-connected system according to a preset compensation margin, the influence coefficient set, and the minimum real part of the eigenvalues; connecting the damper to the underdamped nodes; obtaining the grid-connected point voltage and the three-phase output current of the damper; obtaining three-phase damping modulation waves according to the grid-connected point voltage; obtaining the phase angle by integrating according to the fundamental frequency; obtaining three-phase fundamental modulation waves according to the phase angle and the three-phase output current; modulating to obtain a driving signal after subtracting the three-phase damping modulation waves from the three-phase fundamental modulation waves; driving the damper according to the driving signal; gradually increasing the first coefficient until complete compensation of the damping deficiency is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid control, and in particular, to a damping compensation method and device for a new energy grid-connected system based on an optimized control damper. Background Art

[0002] With the development of new energy technology in the power grid, a large amount of new energy is connected to the power grid through power electronic converters. Due to the characteristics of small inertia, weak damping, and negative damping of power electronic converters, it is easy to cause wide-band oscillation instability problems in the system, seriously threatening the safety of the power system and hindering the grid connection and consumption of new energy.

[0003] Since commercial converters are not open source, it is impossible to optimize the control strategy or parameters of the converters, resulting in difficulties in implementing existing methods for improving the system stability margin through control strategy or parameter optimization to suppress wide-band oscillations in actual engineering. Installing additional dampers to compensate for the system damping to suppress wide-band oscillations is one of the common means in actual engineering. However, how to accurately calculate the damping required for system compensation has become a key issue. In addition, due to the complex operating scenarios and working conditions of the new energy grid-connected system, the existing damper characteristics are difficult to meet the wide-band damping compensation requirements, and the wide-band oscillation suppression effect is not good.

[0004] Therefore, there is an urgent need for a new technical solution to solve the technical problem of how to quantitatively damp the new energy system. Summary of the Invention

[0005] The present invention provides a damping compensation method and device for a new energy grid-connected system based on an optimized control damper to solve the technical problem of how to quantitatively damp the new energy system.

[0006] To achieve the above object, the present invention provides a damping compensation method for a new energy grid-connected system based on an optimized control damper, including:[[]]

[0007] Obtaining underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology.

[0008] Denoting the frequency corresponding to the smallest real part of the eigenvalues as the first frequency; calculating the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the node eigenvalues at the first frequency to obtain a set of influence coefficients.

[0009] Obtaining the damping deficiency of the grid-connected system according to a preset compensation margin, the set of influence coefficients, and the smallest real part of the eigenvalues.

[0010] Setting the switching frequency of the damper to be greater than a preset value and then connecting it to the underdamped node.

[0011] Obtain the grid connection point voltage and three-phase output current of the damper; successively pass each of the three phases of the grid connection point voltage through high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction, and then multiply by the first coefficient to obtain three-phase damping modulation waves; perform integration according to the fundamental frequency to obtain the phase angle; perform Park transformation based on the phase angle and three-phase output current to obtain the d-axis current and q-axis current; take the negative values of the d-axis current and q-axis current, and then add and subtract them from the corresponding current decoupling terms through a PI controller respectively, and perform inverse Park transformation in combination with the phase angle to obtain three-phase fundamental modulation waves.

[0012] Subtract the three-phase fundamental modulation waves from the three-phase damping modulation waves and then obtain the drive signal through pulse width modulation; drive the damper to work according to the drive signal; gradually increase the first coefficient of the damper from 0 until all dampers jointly achieve complete compensation of the damping deficiency.

[0013] Preferably, obtaining the underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology includes:

[0014] Number the bus nodes from 1 to n according to the grid-connected system topology; in the common dq coordinate system, obtain the output impedance or admittance of the new energy converter, the load equivalent impedance, and the equivalent impedance of the line and the grid power supply to construct the nodal admittance matrix.

[0015] Perform eigenvalue decomposition on the nodal admittance matrix within a preset frequency range to obtain 2n eigenvalues; obtain the frequency band corresponding to the eigenvalues with the absolute value of the imaginary part of the eigenvalues less than 0.05 among the 2n eigenvalues to obtain the adjacent oscillation frequency band; within the adjacent oscillation frequency band, obtain all the eigenvalues with the real part of the eigenvalues less than 0 among the 2n eigenvalues to obtain the underdamped eigenvalues; obtain the node numbers corresponding to the underdamped eigenvalues, that is, obtain the underdamped nodes and the eigenvalues of the underdamped nodes.

[0016] Preferably, at the first frequency, calculate the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the node eigenvalue, and the obtained influence coefficient set includes:

[0017] Assume the damper is installed at node , then the influence coefficient at node includes:

[0018] ;

[0019] Among them, represents taking the real part; represents the th element of the th left eigenvector of the nodal admittance matrix; represents the th left eigenvector of the nodal admittance matrix and the element; indicating the -th element of the -th left eigenvector of the nodal admittance matrix; indicating the -th element of the -th left eigenvector of the nodal admittance matrix; .

[0020] By calculating the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the node eigenvalue, the influence coefficient set can be obtained.

[0021] Preferably, the damping shortage of the grid-connected system obtained according to the preset compensation margin, the influence coefficient set and the minimum real part of the eigenvalue includes:

[0022] When there is one underdamped node, the damping shortage includes:

[0023] ;

[0024] where represents the damping shortage of the underdamped node; represents the preset compensation margin; represents the minimum real part of the eigenvalue.

[0025] When there are more than one underdamped nodes, the damping shortage includes:

[0026] ;

[0027] where represents the damping shortage of node ; represents the influence coefficient at node ; .

[0028] Preferably, setting the switching frequency of the damper to be greater than a preset value includes:

[0029] Setting the switching device in the damper to a high-frequency switching device and setting the switching frequency to be greater than 40 kHz.

[0030] Preferably, passing the three phases of the grid connection point voltage through high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction and phase angle lag correction in sequence includes:

[0031] High-frequency signal interference filtering is achieved through the transfer function :

[0032] ;

[0033] Fundamental component filtering is achieved through the transfer function Implementation:

[0034] ;

[0035] Phase lead correction is achieved through the transfer function Implementation:

[0036] ;

[0037] Phase lag correction is achieved through the transfer function Implementation:

[0038] ;

[0039] Among them, represents the cut-off frequency; represents the Laplace operator; represents the center frequency, taking the fundamental frequency; represents the lead coefficient; represents the lead constant; represents the lag coefficient; represents the lag constant.

[0040] Preferably, the lead constant can be expressed as:

[0041] ;

[0042] The lag constant can be expressed as:

[0043] ;

[0044] Among them, represents the lead center frequency; represents the lag center frequency.

[0045] Preferably, the PI controller includes a proportional parameter and an integral parameter .

[0046] The integral parameter takes a preset value; the value of the proportional parameter satisfies:

[0047] ;

[0048] Among them, represents the delay parameter, , represents the switching frequency; represents the inductance value of the filter inductor in the damper, which is determined by the switching frequency of the damper.

[0049] Preferably, starting from 0, the first coefficient of the damper is gradually increased until all the dampers jointly achieve complete compensation for the damping deficiency, which includes:

[0050] The first coefficient is positively correlated with the damping effect of the damper; the output admittance calculation of the damper can be expressed as:

[0051] ;

[0052] Wherein, represents the output admittance of the damper; represents the unit imaginary part; represents the natural base; represents the first coefficient.

[0053] At this time, the damping provided by the damper is ; assuming the first frequency is ; let , then the at the first frequency can be calculated; starting from 0, the first coefficient of the damper is gradually increased, and the damping provided by the damper gradually increases; until all the dampers jointly achieve complete compensation for the damping deficiency, the adjustment of the first coefficient is paused.

[0054] The present invention also provides a damping compensation device for a new energy grid-connected system based on an optimized control damper, which is used for the method of the present invention. The system includes a first module, a second module, a third module, a fourth module, a fifth module and a sixth module.

[0055] The first module is used to obtain the underdamped nodes and the eigenvalues of the underdamped nodes according to the node admittance matrix of the grid-connected system topology; record the frequency corresponding to the minimum real part of the eigenvalues as the first frequency; at the first frequency, calculate the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the node eigenvalue to obtain an influence coefficient set.

[0056] The second module is used to obtain the damping deficiency of the grid-connected system according to the preset compensation margin, the influence coefficient set and the minimum real part of the eigenvalue; set the switching frequency of the damper to be greater than the preset value and then connect it to the underdamped node.

[0057] The third module is used to obtain the grid-connected point voltage and the three-phase output current of the damper.

[0058] The fourth module is used to multiply the three phases of the grid-connected point voltage by the first coefficient after sequentially filtering out high-frequency signal interference, filtering out fundamental wave components, correcting phase angle lead and correcting phase angle lag to obtain three-phase damping modulation waves.

[0059] The fifth module is used to integrate according to the fundamental frequency to obtain the phase angle; perform Park transformation based on the phase angle and the three-phase output current to obtain the d-axis current and the q-axis current; take the negative of the d-axis current and the q-axis current, and then add and subtract them from the corresponding current decoupling terms through a PI controller respectively, and perform inverse Park transformation in combination with the phase angle to obtain the three-phase fundamental modulation wave.

[0060] The sixth module is used to subtract the three-phase damping modulation wave from the three-phase fundamental modulation wave and then obtain the drive signal through pulse width modulation; drive the damper to work according to the drive signal; gradually increase the first coefficient of the damper from 0 until all dampers jointly achieve complete compensation of the damping deficiency.

[0061] The present invention has the following beneficial effects:

[0062] The damping compensation method for a new energy grid-connected system based on an optimized control damper of the present invention obtains the damping deficiency of the grid-connected system according to a preset compensation margin, the influence coefficient set, and the minimum real part of the eigenvalue, so that the method can accurately calculate the damping that needs to be compensated in the new energy grid-connected system. By multiplying the grid connection point voltage after high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction by the first coefficient, a three-phase damping modulation wave is obtained. Integrate according to the fundamental frequency to obtain the phase angle, perform Park transformation based on the phase angle and the three-phase output current to obtain the d-axis current and the q-axis current, take the negative of the d-axis current and the q-axis current, and then add and subtract them from the corresponding current decoupling terms through a PI controller respectively, and perform inverse Park transformation in combination with the phase angle to obtain the three-phase fundamental modulation wave, and drive the damper after processing according to the three-phase damping modulation wave and the three-phase fundamental modulation wave, so that the damper of the method is mainly resistive, has good damping performance, and is suitable for wide-band oscillation suppression; and the adverse effects of the voltage outer loop and the phase-locked loop on the damping effect in the existing damper control technology are avoided during the control process of calculating the three-phase damping modulation wave and the three-phase fundamental modulation wave, so as to better achieve effective suppression of wide-band oscillation. By gradually increasing the first coefficient of the damper from 0 and then making the damper gradually compensate for the system damping deficiency, the method can accurately match the damper with the system damping deficiency and achieve complete compensation of the system damping deficiency, thereby ensuring the safe and stable operation of the power system.

[0063] The damping compensation device for a new energy grid-connected system based on an optimized control damper of the present invention is used for the method of the present invention and has the same beneficial effects as the method of the present invention.

[0064] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The following will refer to the drawings and describe the present invention in further detail. Description of the Drawings

[0065] The accompanying drawings, which form part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0066] Figure 1 is a schematic flow chart of the method of the preferred embodiment of the present invention.

[0067] Figure 2 is a schematic diagram of the optimized control of the damper in the preferred embodiment of the present invention.

[0068] Figure 3 is a schematic diagram of the output admittance characteristic curve of the damper in the preferred embodiment of the present invention.

[0069] Figure 4 is a schematic diagram of the damper effect verification in the preferred embodiment of the present invention. Detailed implementation manners

[0070] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways defined and covered by the claims.

[0071] See Figure 1 , in the preferred embodiment of the present invention, a damping compensation method for a new energy grid-connected system based on an optimized control damper is provided, including:

[0072] S1. Obtain the underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology; Denote the frequency corresponding to the minimum real part of the eigenvalues as the first frequency; At the first frequency, calculate the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the nodal eigenvalue to obtain an influence coefficient set.

[0073] In the preferred embodiment of the present invention, obtaining the underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology includes:

[0074] Number the bus nodes from 1 to n according to the grid-connected system topology; In the common dq coordinate system, obtain the output impedance or admittance of the new energy converter, the load equivalent impedance, and the equivalent impedance of the line and the grid power supply to construct the nodal admittance matrix.

[0075] Among them, the output impedance or admittance of the new energy converter can be calculated according to existing public literature (such as Shang Jiayu, Yu Jiajun, Liu Zeng, etc. Precise frequency-domain modeling and simplified stability criterion of the grid-forming and grid-following inverter parallel system [J]. Automation of Electric Power Systems, 2025, 49(02): 53-63.) or impedance measurement (such as Li Yang, Shuai Zhikang, Fang Junbin, etc. Stability verification method for multi-inverter systems based on impedance measurement [J]. Automation of Electric Power Systems, 2021, 45(11): 95-101.) methods, and the equivalent impedances of the load, line, and grid power supply can be obtained through relevant calculations based on power system analysis knowledge.

[0076] Perform eigenvalue decomposition on the nodal admittance matrix within a preset frequency range to obtain 2n eigenvalues; obtain the frequency band corresponding to the eigenvalues whose absolute value of the imaginary part is less than 0.05 among the 2n eigenvalues to obtain the adjacent oscillation frequency band; within the adjacent oscillation frequency band, obtain all the eigenvalues whose real part is less than 0 among the 2n eigenvalues to obtain the underdamped eigenvalues; obtain the node numbers corresponding to the underdamped eigenvalues, that is, obtain the underdamped nodes and the eigenvalues of the underdamped nodes.

[0077] Obtaining the node numbers corresponding to the underdamped eigenvalues includes:

[0078] Assume that the sequence number of the underdamped eigenvalue among the 2n eigenvalues is ; when is an even number, the underdamped node number is ; when is an odd number, the underdamped node number is .

[0079] In the preferred embodiment of the present invention, at the first frequency, calculate the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the node eigenvalue, and the obtained influence coefficient set includes:

[0080] Assume that the damper is installed at node , then the influence coefficient at node includes:

[0081] ;

[0082] Among them, represents taking the real part; represents the th element of the th left eigenvector of the nodal admittance matrix; represents the th element of the th left eigenvector of the nodal admittance matrix; represents the The -th element of the left eigenvector; Denote the -th element of the left eigenvector of the nodal admittance matrix; ; .

[0083] Calculate the influence coefficient of the real part of the nodal eigenvalue when the damper is installed at each node of the grid-connected system, and then the influence coefficient set can be obtained.

[0084] S2. Obtain the damping deficiency of the grid-connected system according to the preset compensation margin, the influence coefficient set and the minimum real part of the eigenvalue; set the switching frequency of the damper to be greater than the preset value and then connect it to the underdamped node.

[0085] In the preferred embodiment of the present invention, obtaining the damping deficiency of the grid-connected system according to the preset compensation margin, the influence coefficient set and the minimum real part of the eigenvalue includes:

[0086] When there is one underdamped node, the damping deficiency includes:

[0087] ;

[0088] Wherein, Denotes the damping deficiency of the underdamped node; Denotes the minimum real part of the eigenvalue; Denotes the preset compensation margin, The larger the value, the greater the compensation margin, but too large may cause difficulties in the damper design. Therefore, in the preferred embodiment of the present invention

[0089] <0.1 is taken.

[0090] ;

[0091] Wherein, Denotes the damping deficiency of node ; Denotes the influence coefficient at node ; .

[0092] In the preferred embodiment of the present invention, setting the switching frequency of the damper to be greater than the preset value includes:

[0093] Set the switching device in the damper to a high-frequency switching device and set the switching frequency to be greater than 40 kHz.

[0094] The filtering inductor mainly affects the characteristics of the damper output admittance in the medium and high frequency bands. On the premise of meeting the filtering effect (for example, Wu Huabo, Jin Long. Design of a Special Filtering Inductor for Photovoltaic Grid-Connected Inverters [J]. Acta Energiae Solaris Sinica, 2011, 32(07): 963-968. DOI: 10.19912 / j.0254-0096.2011.07.003.), the smaller the filtering inductor, the better. At this time, the switching frequency of the damper should also be increased. In the preferred embodiment of the present invention, high-frequency switching devices such as SiC and GaN are used, and the switching frequency is above 40 kHz. Since the fundamental control loop currents are all taken as 0, the damper hardly participates in the fundamental power transmission. Therefore, even if a high switching frequency is adopted, there is no need to worry about the loss problem. Controlling the switching frequency of the damper to be greater than 40 kHz can control the size of the inductor to be small enough to meet the requirements of the present invention.

[0095] S3. Obtain the grid connection point voltage and three-phase output current of the damper; the three phases of the grid connection point voltage are each multiplied by a first coefficient after sequentially passing through high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction to obtain three-phase damping modulation waves.

[0096] See Figure 2 , the damper of the present invention includes a three-level inverter and a filtering inductor which are composed. The AC side of the three-level inverter is connected in parallel to the bus node; the DC side of the three-level inverter is connected to a DC power supply, and this power supply can also be borne by an energy storage battery.

[0097] In Figure 2 the damping control loop part, the three phases of the grid connection point voltage and are each multiplied by a first coefficient and after passing through transfer functions to obtain three-phase damping modulation waves and .

[0098] In the preferred embodiment of the present invention, sequentially passing the three phases of the grid connection point voltage through high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction includes:

[0099] High-frequency signal interference filtering is achieved through the transfer function :

[0100] ;

[0101] Fundamental component filtering is achieved through the transfer function :

[0102] ;

[0103] The phase - angle lead correction is achieved through the transfer function as follows:

[0104] ;

[0105] The phase - angle lag correction is achieved through the transfer function as follows:

[0106] ;

[0107] Among them, represents the cut - off frequency, and its value - taking principle is 1.5 times the upper - limit damping frequency. The upper - limit damping frequency refers to the maximum frequency at which the desired damper can achieve an effective damping effect; represents the Laplace operator; represents the center frequency, taking the fundamental frequency; represents the lead coefficient, taking 0.5; represents the lead constant; represents the lag coefficient, taking 2; represents the lag constant.

[0108] In the preferred embodiment of the present invention, the lead constant can be expressed as:

[0109] ;

[0110] The lag constant can be expressed as:

[0111] ;

[0112] Among them, represents the lead center frequency, taking 20Hz; represents the lag center frequency, taking 60Hz.

[0113] S4. Integrate according to the fundamental frequency to obtain the phase angle; perform Park transformation based on the phase angle and the three - phase output current to obtain the d - axis current and the q - axis current; take the negative of the d - axis current and the q - axis current, and then add and subtract them from the corresponding current decoupling terms through a PI controller respectively, and combine with the phase angle to perform inverse Park transformation to obtain the three - phase fundamental modulation wave.

[0114] In Figure 2 the fundamental - wave control - loop part, integrate according to the fundamental frequency to obtain the phase angle ; perform Park transformation based on the phase angle and the three - phase output current to obtain the d - axis current and the q - axis current ; take the d - axis current and the q-axis current are respectively subtracted from their reference values and wherein and both take values of 0, and the differences are respectively added to the current decoupling terms after passing through a PI controller (proportional-integral controller), and then through an inverse Park transformation (i.e., dq / abc transformation) to obtain the three-phase fundamental modulation waves and .

[0115] In the preferred embodiment of the present invention, the phase angle used in the Park transformation is obtained by integrating the fundamental wave frequency , and a phase-locked loop is not adopted, which has the advantage of eliminating the adverse effects brought by the phase-locked loop under a weak power grid; the grid voltage feedforward control is not adopted, avoiding the situation of weakening the damping effect of the damper.

[0116] In the preferred embodiment of the present invention, the PI controller includes a proportional parameter and an integral parameter .

[0117] The integral parameter takes a preset value, and in the preferred embodiment of the present invention, the preferred value is 50;

[0118] The value of the proportional parameter satisfies:

[0119] ;

[0120] wherein represents a delay parameter, , represents the switching frequency; represents the inductance value of the filter inductor in the damper, which is determined by the switching frequency of the damper.

[0121] S5. Subtract the three-phase damping modulation wave from the three-phase fundamental modulation wave and then obtain the drive signal through pulse width modulation; drive the damper to work according to the drive signal; gradually increase the first coefficient of the damper from 0 until all dampers jointly achieve complete compensation of the damping deficit.

[0122] In Figure 2 , the three-phase fundamental modulation wave and are respectively subtracted from the three-phase damping modulation wave and and then the drive signal can be obtained through pulse width modulation (PWM).

[0123] In a preferred embodiment of the present invention, gradually increasing the first coefficient of the damper from 0 until all dampers jointly achieve complete compensation for the damping deficit includes:

[0124] The first coefficient is positively correlated with the damping effect of the damper; the output admittance calculation of the damper can be expressed as:

[0125] ;

[0126] Wherein, represents the output admittance of the damper; represents the unit imaginary part; represents the natural base; represents the first coefficient.

[0127] At this time, the damping provided by the damper is ; assuming the first frequency is ; let , then the at the first frequency can be calculated; gradually increasing the first coefficient of the damper from 0, the damping provided by the damper gradually increases; until all dampers jointly achieve complete compensation for the damping deficit, the adjustment of the first coefficient is paused.

[0128] The damping compensation method for a new energy grid-connected system based on an optimized control damper of the present invention obtains the damping deficit of the grid-connected system according to a preset compensation margin, the influence coefficient set, and the minimum real part of the eigenvalue, so that the method can accurately calculate the damping required to be compensated by the new energy grid-connected system. By multiplying the grid connection point voltage after high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction by the first coefficient, a three-phase damping modulation wave is obtained. Integrating according to the fundamental frequency to obtain the phase angle, performing Park transformation on the phase angle and the three-phase output current to obtain the d-axis current and the q-axis current. After taking the negative of the d-axis current and the q-axis current, they are respectively added and subtracted with the corresponding current decoupling terms through a PI controller, and combined with the phase angle for inverse Park transformation to obtain a three-phase fundamental modulation wave. And after processing the three-phase damping modulation wave and the three-phase fundamental modulation wave, the damper is driven, so that the damper of the method is mainly resistive, has good damping performance, and is suitable for wide-band oscillation suppression; and in the control process of calculating the three-phase damping modulation wave and the three-phase fundamental modulation wave, the adverse effects of the voltage outer loop and the phase-locked loop in the existing damper control technology on the damping effect are avoided, thereby better realizing the effective suppression of wide-band oscillation. By gradually increasing the first coefficient of the damper from 0 and then making the damper gradually compensate for the system damping deficit, the method can accurately match the damper with the system damping deficit and achieve complete compensation for the system damping deficit.

[0129] A damping compensation device for a new energy grid-connected system based on an optimized control damper is also provided in a preferred embodiment of the present invention, which is used for the method of the present invention. The system includes a first module, a second module, a third module, a fourth module, a fifth module, and a sixth module.

[0130] The first module is used to obtain the underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology; record the frequency corresponding to the smallest real part of the eigenvalues as the first frequency; at the first frequency, calculate the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the nodal eigenvalue, and obtain a set of influence coefficients.

[0131] The second module is used to obtain the damping deficiency of the grid-connected system according to the preset compensation margin, the set of influence coefficients, and the smallest real part of the eigenvalue; set the switching frequency of the damper to be greater than the preset value and then connect it to the underdamped node.

[0132] The third module is used to obtain the grid-connected point voltage and the three-phase output current of the damper.

[0133] The fourth module is used to multiply each of the three phases of the grid-connected point voltage by a first coefficient after sequentially passing through high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction to obtain three-phase damping modulation waves.

[0134] The fifth module is used to integrate according to the fundamental frequency to obtain the phase angle; perform Park transformation according to the phase angle and the three-phase output current to obtain the d-axis current and the q-axis current; take the negative values of the d-axis current and the q-axis current and add and subtract them from the corresponding current decoupling terms through a PI controller respectively, and combine with the phase angle to perform inverse Park transformation to obtain three-phase fundamental modulation waves.

[0135] The sixth module is used to obtain a driving signal through pulse width modulation after subtracting the three-phase damping modulation waves from the three-phase fundamental modulation waves; drive the damper to work according to the driving signal; gradually increase the first coefficient of the damper from 0 until all dampers jointly achieve complete compensation of the damping deficiency.

[0136] The damping compensation device for the new energy grid-connected system based on the optimized control damper of the present invention, which is used for the method of the present invention, has the same beneficial effects as the method of the present invention.

[0137] Verification part:

[0138] In a preferred embodiment of the present invention, a certain new energy grid-connected system is taken as an example to verify the effectiveness of the method of the present invention.

[0139] Figure 3 is the output admittance characteristic curve of the optimized control damper of the present invention. From Figure 3It can be seen that in the frequency range of 1 Hz - 2 kHz, only the phase angle is slightly larger near 50 Hz (corresponding to the fundamental frequency), and the phase angle of the overall damper output admittance is relatively small (the phase angle in the entire frequency band is between -40° and 25°), indicating that the optimized control damper designed by the present invention is mainly resistive, so it has good damping characteristics.

[0140] Figure 4 This is the case system simulation waveform of the preferred embodiment of the present invention. In the simulation, the optimized control damper of the present invention is connected to the system within the time range of 0 - 2 s, and the grid current is stable; at the moment of 2 s, the optimized control damper of the present invention is removed, and it can be seen that the grid current waveform becomes unstable and distorted after 2 s, thereby verifying the effectiveness of the method of the present invention for improving the stability of the new energy grid-connected system.

[0141] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A damping compensation method for a new energy grid-connected system based on an optimized control damper, characterized in that, Including: Obtaining the underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology; Denoting the frequency corresponding to the minimum real part of the eigenvalues as the first frequency; at the first frequency, calculating the influence coefficients of the damping device installed at each node of the grid-connected system on the real part of the nodal eigenvalues to obtain a set of influence coefficients; Obtaining the damping deficiency of the grid-connected system according to a preset compensation margin, the set of influence coefficients, and the minimum real part of the eigenvalues; Setting the switching frequency of the damping device to be greater than a preset value and then connecting it to the underdamped node; Obtaining the grid connection point voltage and the three-phase output current of the damping device; multiplying each of the three phases of the grid connection point voltage by a first coefficient after successively filtering out high-frequency signal interference, filtering out fundamental components, correcting phase angle lead, and correcting phase angle lag to obtain three-phase damping modulation waves; integrating according to the fundamental frequency to obtain a phase angle; performing Park transformation on the phase angle and the three-phase output current to obtain d-axis current and q-axis current; taking the negative of the d-axis current and q-axis current and adding and subtracting them from the corresponding current decoupling terms through a PI controller respectively, and combining with the phase angle to perform inverse Park transformation to obtain three-phase fundamental modulation waves; Subtracting the three-phase damping modulation waves from the three-phase fundamental modulation waves and then obtaining a driving signal through pulse width modulation; driving the damping device to work according to the driving signal; gradually increasing the first coefficient of the damping device from 0 until all the damping devices jointly achieve complete compensation of the damping deficiency.

2. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 1, characterized in that The obtaining the underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology includes: Numbering the bus nodes from 1 to n according to the grid-connected system topology; in the common dq coordinate system, obtaining the output impedance or admittance of the new energy converter, the load equivalent impedance, and the equivalent impedance of the line and the grid power supply to construct the nodal admittance matrix; Performing eigenvalue decomposition on the nodal admittance matrix within a preset frequency range to obtain 2n eigenvalues; obtaining the frequency band corresponding to the eigenvalues whose absolute value of the imaginary part is less than 0.05 among the 2n eigenvalues to obtain an adjacent oscillation frequency band; within the adjacent oscillation frequency band, obtaining all the eigenvalues whose real part is less than 0 among the 2n eigenvalues to obtain underdamped eigenvalues; obtaining the node numbers corresponding to the underdamped eigenvalues, that is, obtaining the underdamped nodes and the eigenvalues of the underdamped nodes.

3. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 2, wherein, Calculating the influence coefficients of the damping device installed at each node of the grid-connected system on the real part of the nodal eigenvalues at the first frequency to obtain a set of influence coefficients includes: Assume that the damper is installed at the node , then the influence coefficient at node includes: ​ ； Among them, represents taking the real part; represents the -th element of the -th left eigenvector of the nodal admittance matrix; represents the -th element of the -th left eigenvector of the nodal admittance matrix; represents the -th element of the -th left eigenvector of the nodal admittance matrix; represents the -th element of the -th left eigenvector of the nodal admittance matrix; ; Calculating the influence coefficients of the damping device installed at each node of the grid-connected system on the real part of the nodal eigenvalues, and then the set of influence coefficients can be obtained.

4. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 3, characterized in that, Obtaining the damping deficiency of the grid-connected system according to a preset compensation margin, the set of influence coefficients, and the minimum real part of the eigenvalues includes: When there is one underdamped node, the damping deficiency includes: ； Among them, represents the damping deficiency of the underdamped node; represents the preset compensation margin; represents the minimum real part of the eigenvalue; When there are more than one underdamped nodes, the damping deficiency includes: ； Among them, represents the damping deficiency of the node ; represents the influence coefficient at the node ; .

5. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 4, wherein, The setting the switching frequency of the damping device to be greater than a preset value includes: Setting the switching device in the damping device as a high-frequency switching device and setting the switching frequency to be greater than 40 kHz.

6. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 5, characterized in that, Sequentially passing the three phases of the grid connection point voltage through high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction includes: The high-frequency signal interference filtering is achieved through the transfer function as follows: ； The fundamental component filtering is achieved through the transfer function as follows: ； The phase angle lead correction is achieved through the transfer function as follows: ； The phase angle lag correction is achieved through the transfer function as follows: ； Among them, represents the cut-off frequency; represents the Laplace operator; represents the center frequency, taking the fundamental frequency; α represents the lead coefficient; represents the lead constant; represents the lag coefficient; represents the lag constant.

7. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 6, characterized in that, The leading constant can be expressed as: ； The hysteresis constant can be expressed as: ； Among them, represents the leading center frequency; represents the lagging center frequency.

8. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 7, characterized in that The PI controller includes a proportional parameter and an integral parameter ; The integral parameter takes a preset value; the proportional parameter is such that: ； Among them, represents the delay parameter, , represents the switching frequency; represents the inductance value of the filter inductor in the damper, which is determined by the switching frequency of the damper.

9. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 8, characterized in that, Gradually increasing the first coefficient of the damper from 0 until all dampers jointly achieve complete compensation for the damping deficiency includes: The first coefficient is positively correlated with the damping effect of the damper; the calculation of the output admittance of the damper can be expressed as: ； Among them, represents the output admittance of the damper; represents the unit imaginary part; represents the natural base; represents the first coefficient; At this time, the damping provided by the damper is ; assuming that the first frequency is ; let , then the at the first frequency can be calculated; gradually increase the first coefficient of the damper starting from 0, then the damping provided by the damper gradually increases; until all dampers jointly achieve the complete compensation of the damping deficit, pause adjusting the first coefficient.

10. A damping compensation device for a new energy grid-connected system based on an optimized control damper, which is used for the method according to any one of claims 1 to 9, characterized in that, The system includes a first module, a second module, a third module, a fourth module, a fifth module, and a sixth module; The first module is used to obtain the underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology; Denote the frequency corresponding to the minimum real part of the eigenvalues as the first frequency; at the first frequency, calculate the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the nodal eigenvalue to obtain a set of influence coefficients; The second module is used to obtain the damping deficiency of the grid-connected system according to a preset compensation margin, the set of influence coefficients, and the minimum real part of the eigenvalue; set the switching frequency of the damper to be greater than a preset value and then connect it to the underdamped node; The third module is used to obtain the grid connection point voltage and the three-phase output current of the damper; The fourth module is used to multiply the three phases of the grid connection point voltage, which have been sequentially passed through high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction, by the first coefficient to obtain three-phase damping modulation waves; The fifth module is used to integrate according to the fundamental frequency to obtain a phase angle; perform Park transformation according to the phase angle and the three-phase output current to obtain the d-axis current and the q-axis current; take the negative of the d-axis current and the q-axis current and add and subtract them from the corresponding current decoupling terms through a PI controller respectively, and combine with the phase angle to perform inverse Park transformation to obtain three-phase fundamental modulation waves; The sixth module is used to obtain a driving signal through pulse width modulation after subtracting the three-phase damping modulation waves from the three-phase fundamental modulation waves; drive the damper to work according to the driving signal; gradually increase the first coefficient of the damper from 0 until all dampers jointly achieve complete compensation for the damping deficiency.

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