New energy grid-connected system damping compensation method and device based on optimized control damper

Abstract

The invention discloses a new energy grid-connected system damping compensation method and device based on an optimized control damper. The method comprises the steps that under-damping nodes and characteristic values of the under-damping nodes are obtained according to a node admittance matrix of a grid-connected system topology; recording the frequency corresponding to the minimum real part of the characteristic value in the characteristic values as a first frequency; under the first frequency, calculating an influence coefficient set of the damper; according to the preset compensation margin, the influence coefficient set and the minimum real part of the characteristic value, the damping shortage of the grid-connected system is obtained; a damper is connected to the under-damping node; acquiring grid-connected point voltage and three-phase output current of the damper; obtaining a three-phase damping modulation wave according to the grid-connected point voltage; performing integration according to the fundamental wave frequency to obtain a phase angle; obtaining a three-phase fundamental wave modulation wave according to the phase angle and the three-phase output current; subtracting the three-phase damping modulation wave from the three-phase fundamental modulation wave, and then performing modulation to obtain a driving signal; driving the damper according to the driving signal; and gradually increasing the first coefficient until the complete compensation of the damping deficiency is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid control, and particularly 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 technologies in the power grid, large-scale 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 in practical engineering the existing methods of improving the system stability margin through optimizing control strategies or parameters to suppress wide-band oscillations. Installing additional dampers to compensate for the system damping to suppress wide-band oscillations is one of the commonly used means in practical 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 characteristics of existing dampers are difficult to meet the wide-band damping compensation requirements, and the effect of suppressing wide-band oscillations 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: Obtaining underdamped nodes and the eigenvalues of the underdamped nodes according to the nodal admittance matrix of the grid-connected system topology.

[0007] Denoting the frequency corresponding to the minimum 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 nodal eigenvalue at the first frequency to obtain a set of influence coefficients.

[0008] Obtaining the damping shortage of the grid-connected system according to a preset compensation margin, the set of influence coefficients, and the minimum real part of the eigenvalues.

[0009] Setting the switching frequency of the damper to be greater than a preset value and then connecting it to the underdamped node.

[0010] Obtain the grid connection point voltage and three-phase output current of the damper; multiply each of the three phases of the grid connection 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; 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 of the d-axis current and q-axis current, 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.

[0011] Subtract the three-phase damping modulation waves from the three-phase fundamental modulation waves and obtain the driving signal through pulse width modulation; 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.

[0012] 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: 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.

[0013] 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.

[0014] Preferably, at the first frequency, calculate the influence coefficients of the damper installed at each node of the grid-connected system on the real part of the node eigenvalues, and the obtained set of influence coefficients includes: Assume the damper is installed at node , then the influence coefficient at node includes: ; Wherein, 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; denotes the th element of the left eigenvector of the nodal admittance matrix; .

[0015] By calculating the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the nodal eigenvalue, the influence coefficient set can be obtained.

[0016] Preferably, the damping deficiency of the grid-connected system is obtained based on a preset compensation margin, the influence coefficient set, and the minimum real part of the eigenvalue, including: When there is one underdamped node, the damping deficiency includes: ; where, denotes the damping deficiency of the underdamped node; denotes the preset compensation margin; denotes the minimum real part of the eigenvalue.

[0017] When there are more than one underdamped nodes, the damping deficiency includes: ; where, denotes the damping deficiency of node ; denotes the influence coefficient at node ; .

[0018] Preferably, setting the switching frequency of the damper to be greater than a preset value includes: Setting the switching device in the damper to a high-frequency switching device and setting the switching frequency to be greater than 40 kHz.

[0019] Preferably, passing the three phases of the grid-connected point voltage through high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction includes: High-frequency signal interference filtering is achieved through the transfer function : ; Fundamental component filtering is achieved through the transfer function : ; Phase angle lead correction is achieved through the transfer function : ; Phase angle lag correction is achieved through the transfer function : ​ ; 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.

[0020] Preferably, the lead constant can be expressed as: ; The lag constant can be expressed as: ; Among them, represents the lead center frequency; represents the lag center frequency.

[0021] Preferably, the PI controller includes a proportional parameter and an integral parameter .

[0022] The integral parameter takes a preset value; the value of the proportional parameter satisfies: ; 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.

[0023] Preferably, 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 output admittance calculation 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.

[0024] At this time, the damping provided by the damper is ; assuming the first frequency is ; let , the value at the first frequency can be calculated ; starting from 0, gradually increase the first coefficient of the damper, then the damping provided by the damper gradually increases; until all dampers jointly achieve complete compensation for the damping shortage, pause adjusting the first coefficient.

[0025] 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.

[0026] 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 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, and obtain a set of influence coefficients.

[0027] The second module is used to obtain the damping shortage of the grid-connected system according to the preset compensation margin, the set of influence coefficients and the minimum real part of the eigenvalues; set the switching frequency of the damper to be greater than a preset value and then connect it to the underdamped nodes.

[0028] The third module is used to obtain the grid-connected point voltage and the three-phase output current of the damper.

[0029] The fourth module is used to multiply each of the three phases of the grid-connected point voltage by the 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.

[0030] 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 d-axis current and 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.

[0031] The sixth module is used to subtract the three-phase damping modulation waves from the three-phase fundamental modulation waves and then obtain a driving signal through pulse width modulation; 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 shortage.

[0032] The present invention has the following beneficial effects: The damping compensation method for a new energy grid-connected system based on an optimized control damper according to the present invention obtains the damping deficiency of the grid-connected system based on a preset compensation margin, the influence coefficient set, and the minimum real part of the eigenvalue, enabling the method to accurately calculate the damping to be compensated in the new energy grid-connected system. By multiplying the grid connection point voltage, after high-frequency signal interference filtering, fundamental wave component filtering, phase angle lead correction, and phase angle lag correction, by a first coefficient, a three-phase damping modulation wave is obtained. Integrating according to the fundamental wave frequency to obtain a phase angle, performing a Park transformation based 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 values of the d-axis current and the q-axis current, adding and subtracting them respectively from the corresponding current decoupling terms through a PI controller, and combining with the phase angle to perform an inverse Park transformation to obtain a three-phase fundamental wave modulation wave. After processing based on the three-phase damping modulation wave and the three-phase fundamental wave modulation wave to drive the damper, the damper of the method is mainly resistive, has good damping performance, and is suitable for wide-band oscillation suppression. Also, during the control process of calculating the three-phase damping modulation wave and the three-phase fundamental wave 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 achieving the effective suppression of wide-band oscillation. By gradually increasing the first coefficient of the damper starting from 0 to 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, thus ensuring the safe and stable operation of the power system.

[0033] The damping compensation device for a new energy grid-connected system based on an optimized control damper according to 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.

[0034] In addition to the purposes, features, and advantages described above, the present invention has other purposes, features, and advantages. The following will refer to the accompanying drawings for a further detailed description of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is a schematic flowchart of the method of the preferred embodiment of the present invention.

[0036] Figure 2 is a schematic diagram of the optimized control of the damper of the preferred embodiment of the present invention.

[0037] Figure 3 is a schematic diagram of the output admittance characteristic curve of the damper of the preferred embodiment of the present invention.

[0038] Figure 4 is a schematic diagram of the damping effect verification of the preferred embodiment of the present invention. Detailed implementation manners

[0039] 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.

[0040] See Figure 1 , in a 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: S1. 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 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, and obtain the influence coefficient set.

[0041] In a 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: 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 equivalent impedance of the load, and the equivalent impedance of the line and the grid power supply to construct the nodal admittance matrix.

[0042] 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 for the parallel system of grid-forming and grid-following inverters [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 impedance of the load, line, and grid power supply can be obtained through relevant calculations based on power system analysis knowledge.

[0043] 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 less than 0.05 among the 2n eigenvalues, and obtain the adjacent oscillation frequency band; within the adjacent oscillation frequency band, obtain all the eigenvalues with the real part less than 0 among the 2n eigenvalues, and 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.

[0044] Obtaining the node numbers corresponding to the underdamped eigenvalues includes: 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 When it is odd, the underdamped node number is .

[0045] In a preferred embodiment of the present invention, at the first frequency, the influence coefficient of the damper installed at each node of the grid-connected system on the real part of the node eigenvalue is calculated, and the obtained influence coefficient set includes: Assume that the damper is installed at node , then the influence coefficient at node includes: ; wherein, denotes taking the real part; denotes the th element of the th left eigenvector of the node admittance matrix; denotes the th element of the th left eigenvector of the node admittance matrix; denotes the th element of the th left eigenvector of the node admittance matrix; denotes the th element of the th left eigenvector of the node admittance matrix; .

[0046] 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.

[0047] 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.

[0048] In a 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: When there is one underdamped node, the damping deficiency includes: ; 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 of , the greater the compensation margin, but too large may cause difficulties in the damper design. Therefore, in a preferred embodiment of the present invention

[0049] When there is more than one underdamped node, the damping deficiency includes: ; Among them, represents the damping deficiency of node ; represents the influence coefficient at node ; .

[0050] In a preferred embodiment of the present invention, setting the switching frequency of the damper to be greater than a preset value includes: Setting the switching device in the damper to a high-frequency switching device and setting the switching frequency to be greater than 40 kHz.

[0051] The filter 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 special filter inductors 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 filter inductor, the better; at this time, the switching frequency of the damper should also be increased. In a 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 current 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.

[0052] S3. Obtain the grid connection point voltage and three-phase output current of the damper; multiply each of the three phases of the grid connection 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.

[0053] See Figure 2 , the damper of the present invention includes a three-level inverter and a filter 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.

[0054] In Figure 2 of the damping control loop part, each of the three phases of the grid connection point voltage and are sequentially multiplied by a first coefficient and after passing through transfer functions to obtain three-phase damping modulation waves and .

[0055] In the preferred embodiment of the present invention, the three phases of the grid connection point voltage are sequentially subjected to high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction, and phase angle lag correction, including: The high-frequency signal interference filtering is achieved through the transfer function : ; The fundamental component filtering is achieved through the transfer function : ; The phase angle lead correction is achieved through the transfer function : ; The phase angle lag correction is achieved through the transfer function : ; 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.

[0056] In the preferred embodiment of the present invention, the lead constant can be expressed as: ; The lag constant can be expressed as: ; Among them, represents the lead center frequency, taking 20 Hz; represents the lag center frequency, taking 60 Hz.

[0057] S4. Integrate according to the fundamental frequency to obtain the phase angle; perform Park transformation 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 add and subtract them from the corresponding current decoupling terms through a PI controller, and combine with the phase angle to perform an inverse Park transformation to obtain the three-phase fundamental modulation wave.

[0058] In Figure 2In the fundamental wave control loop section, according to the fundamental wave frequency perform integration to obtain the phase angle ; according to the phase angle and the three-phase output current, perform Park transformation to obtain the d-axis current and the q-axis current ; subtract the d-axis current and the q-axis current from their respective reference values and respectively, where and both take values of 0. The differences, after passing through a PI controller (proportional-integral controller), are added to the current decoupling terms respectively, and then through the inverse Park transformation (i.e., dq / abc transformation) to obtain the three-phase fundamental wave modulation waves and .

[0059] In the preferred embodiment of the present invention, the phase angle used for the Park transformation is obtained by integrating the fundamental wave frequency , and a phase-locked loop is not used. The advantage is that it can eliminate the adverse effects brought by the phase-locked loop under a weak power grid; the grid voltage feed-forward control is not used, avoiding the situation of weakening the damping effect of the damper.

[0060] In the preferred embodiment of the present invention, the PI controller includes a proportional parameter and an integral parameter .

[0061] The integral parameter takes a preset value, and in the preferred embodiment of the present invention, the preferred value is 50; The value of the proportional parameter satisfies: ; where 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.

[0062] S5. Subtract the three-phase damping modulation wave from the three-phase fundamental wave 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.

[0063] In Figure 2 , the three-phase fundamental wave modulation waves and correspondingly subtract the three-phase damping modulation waves and The driving signal can be obtained through pulse width modulation (PWM).

[0064] 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 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: ; wherein, represents the output admittance of the damper; represents the unit imaginary part; represents the natural base; represents the first coefficient.

[0065] At this time, the damping provided by the damper is ; assuming the first frequency is ; let , 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 deficiency, the adjustment of the first coefficient is paused.

[0066] 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 this method can accurately calculate the damping that needs to be compensated for 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, and 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 from 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 this 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, 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 deficiency, this method can accurately match the damper with the system damping deficiency and achieve complete compensation for the system damping deficiency.

[0067] A damping compensation device for a new energy grid-connected system based on an optimized control damper is further 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.

[0068] The first module is configured to obtain 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 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, and obtain a set of influence coefficients.

[0069] The second module is configured to obtain the damping shortage 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.

[0070] The third module is configured to obtain the grid-connected point voltage and three-phase output current of the damper.

[0071] The fourth module is configured to multiply each of the three phases of the grid-connected point voltage by a first coefficient after sequentially filtering out high-frequency signal interference, filtering out fundamental components, correcting the phase angle lead, and correcting the phase angle lag to obtain three-phase damping modulation waves.

[0072] The fifth module is configured to integrate according to the fundamental frequency to obtain a phase angle; perform Park transformation on the phase angle and the three-phase output current to obtain d-axis current and q-axis current; take the negative of the d-axis current and q-axis current and add and subtract them from the corresponding current decoupling terms through a PI controller respectively, and combine the phase angle to perform inverse Park transformation to obtain three-phase fundamental modulation waves.

[0073] The sixth module is configured to subtract the three-phase damping modulation waves from the three-phase fundamental modulation waves and then obtain a driving signal through pulse width modulation; 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 shortage.

[0074] 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.

[0075] Verification part: 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.

[0076] 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 whole 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.

[0077] Figure 4 This is the case system simulation waveform of the preferred embodiment of the present invention. During 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, thus verifying the effectiveness of the method of the present invention for improving the stability of the new energy grid-connected system.

[0078] The above are only the preferred embodiments of the present invention and are not used 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: include: Obtaining the underdamped nodes and eigenvalues ​​of the underdamped nodes according to the node admittance matrix of the grid-connected system topology; Recording the frequency corresponding to the minimum real part of the eigenvalue in the eigenvalue as the first frequency; at the first frequency, calculating the influence coefficient of the real part of the node eigenvalue when the damper is installed at each node of the grid-connected system to obtain an influence coefficient set; 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; The switching frequency of the damper is set to be greater than a preset value and then connected to the under-damped node; Obtain the grid-connected point voltage and three-phase output current of the damper; subject the three phases of the grid-connected point voltage to high-frequency signal interference filtering, fundamental component filtering, phase angle lead correction and phase angle lag correction in sequence, and then multiply them with the first coefficient to obtain a three-phase damped modulation wave; integrate according to the fundamental frequency to obtain the phase angle; perform Parker transformation according to the phase angle and the three-phase output current to obtain the d-axis current and the q-axis current; negate the d-axis current and the q-axis current, respectively add and subtract them from the corresponding current decoupling terms through a PI controller, and perform an inverse Parker transformation in combination with the phase angle to obtain a three-phase fundamental modulation wave; The driving signal is obtained by pulse width modulation after subtracting the three-phase damping modulation wave from the three-phase fundamental modulation wave; the damper is driven to work according to the driving signal; and the first coefficient of the damper is gradually increased from 0 until all the dampers 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 is characterized in that: The method of obtaining the underdamped node and the eigenvalue of the underdamped node according to the node admittance matrix of the grid-connected system topology includes: The busbar nodes are numbered from 1 to n according to the grid-connected system topology; in a common dq coordinate system, the output impedance or admittance of the new energy converter, the load equivalent impedance, and the line and grid power equivalent impedance are obtained to construct the node admittance matrix; Perform eigenvalue decomposition on the node admittance matrix within a preset frequency range to obtain 2n eigenvalues; obtain the frequency band corresponding to the eigenvalue whose absolute value of the imaginary part of the eigenvalue is less than 0.05 among the 2n eigenvalues ​​to obtain an adjacent oscillation frequency band; within the adjacent oscillation frequency band, obtain all eigenvalues ​​whose real part of the eigenvalue is less than 0 among the 2n eigenvalues ​​to obtain an underdamped eigenvalue; obtain the node number corresponding to the underdamped eigenvalue, that is, obtain the underdamped node and the eigenvalue of the underdamped node.

3. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 2 is characterized in that: At the first frequency, the influence coefficient of the real part of the node eigenvalue when the damper is installed at each node of the grid-connected system is calculated, and the influence coefficient set obtained includes: Assume that the damper is installed at the node , then the node The influence coefficient include: ； in, represents taking the real part; represents the node admittance matrix The left eigenvector elements; represents the node admittance matrix The left eigenvector elements; represents the node admittance matrix The left eigenvector elements; represents the node admittance matrix The left eigenvector elements; ; The influence coefficient set can be obtained by calculating the influence coefficient of the real part of the node eigenvalue when the damper is installed at each node of the grid-connected system.

4. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 3 is characterized in that: 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: When there is one underdamped node, the damping deficiency includes: ； in, represents the damping deficiency of the underdamped node; represents the preset compensation margin; represents the minimum real part of the eigenvalue; When the underdamped node is greater than one, the damping deficiency includes: ； in, Representation Node The damping gap; Representation Node The influence coefficient of .

5. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 4 is characterized in that: The step of setting the switching frequency of the damper to be greater than a preset value comprises: The switching device in the damper is set to a high-frequency switching device, and the switching frequency is set 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 is characterized in that: The three phases of the grid connection point voltage are sequentially subjected to high-frequency signal interference filtering, fundamental component filtering, phase angle leading correction and phase angle lagging correction, including: The high frequency interference signal is filtered out by the transfer function accomplish: ； The fundamental component is filtered out by the transfer function accomplish: ； The phase angle advance correction is achieved by the transfer function accomplish: ； The phase angle lag is corrected by the transfer function accomplish: ； in, represents the cut-off frequency; represents the Laplace operator; Indicates the center frequency, taking the fundamental frequency; α represents the leading coefficient; represents a look-ahead constant; represents the hysteresis coefficient; Represents the hysteresis constant.

7. The damping compensation method for a new energy grid-connected system based on an optimized control damper according to claim 6 is characterized in that: The advance constant It can be expressed as: ； The hysteresis constant It can be expressed as: ； in, Indicates the leading center frequency; Indicates the lag 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 the integral parameter ; The integration parameter Take the preset value; the ratio parameter The value of satisfies: ； in, Indicates the delay parameter, , Indicates the switching frequency; It 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: The step of gradually increasing the first coefficient of the damper from 0 until all dampers jointly achieve complete compensation of the damping deficiency comprises: The first coefficient is positively correlated with the damping effect of the damper; the output admittance calculation of the damper can be expressed as: ； in, 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 ; Assume that the first frequency is ;make , we can calculate the first frequency ; Starting from 0, gradually increase the first coefficient of the damper, then the damping provided by the damper gradually increases; until all dampers jointly achieve full compensation of the damping deficiency, suspend adjusting the first coefficient.

10. A damping compensation device for a new energy grid-connected system based on an optimized control damper, used in the method according to any one of claims 1 to 9, characterized in that: The system comprises 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 underdamped nodes and eigenvalues ​​of underdamped nodes according to the node admittance matrix of the grid-connected system topology; Recording the frequency corresponding to the minimum real part of the eigenvalue in the eigenvalue as the first frequency; at the first frequency, calculating the influence coefficient of the real part of the node eigenvalue when the damper is installed at each node of the grid-connected system to obtain an influence coefficient set; 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; and connect the under-damped node after setting the switching frequency of the damper to be greater than the preset value; The third module is used to obtain the grid connection point voltage and three-phase output current of the damper; The fourth module is used to sequentially filter out high-frequency signal interference, filter out fundamental components, perform phase angle advance correction and phase angle lag correction on the three phases of the grid connection point voltage, and then multiply the three phases by the first coefficient to obtain a three-phase damped modulation wave; The fifth module is used to integrate the fundamental frequency to obtain the phase angle; perform Parker transformation according to the phase angle and the three-phase output current to obtain the d-axis current and the q-axis current; after the d-axis current and the q-axis current are negative, they are added and subtracted from the corresponding current decoupling terms through the PI controller, and an inverse Parker transformation is performed in combination with the phase angle to obtain a three-phase fundamental modulation wave; The sixth module is used to obtain a driving signal by pulse width modulation after subtracting the three-phase damping modulation wave from the three-phase fundamental modulation wave; drive the damper to work according to the driving signal; and gradually increase the first coefficient of the damper from 0 until all dampers jointly achieve complete compensation of the damping deficiency.

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