A method and device for SVG-based additional subsynchronous damping control without phase shifting

Abstract

The application discloses a SVG-based non-phase-shifting additional subsynchronous damping control method and device, from the perspective of a SVG reactive power compensation device, additional damping control is exerted on the current inner loop control of the SVG, voltage and current components when subsynchronous oscillation occurs are introduced, and the oscillation frequency bands of the voltage and current components are extracted by using FFT respectively, the influence between each input component and the subsynchronous oscillation component is fully considered, and the system subsynchronous oscillation problem caused by the interaction between a new energy unit and the SVG is effectively inhibited.

Description

Technical Field

[0001] This invention belongs to the field of power electronic power system control technology, specifically relating to an additional subsynchronous damping control method and device for subsynchronous oscillations caused by a doubly fed wind turbine and a static var compensator (SVG). Background Technology

[0002] In recent years, with the increasing awareness of environmental protection and energy conservation and emission reduction, new energy sources have been vigorously developed. Compared with traditional power grids, large-scale new energy power plant clusters have more complex structures and characteristics, and are often located at the end of the power grid, providing weaker support to the AC side system. Furthermore, with the widespread application of DC transmission of new energy, the trend towards power electronics in power systems is obvious, which may pose new threats to the safe and stable operation of the system. For example, when the power grid is subjected to small disturbances, a power system with a high proportion of power electronics can adjust the state of each component of the system using only conventional control. Under the control of different bandwidth loops, the components of the system form a structure with multi-scale cascade characteristics. The interaction between these devices may trigger oscillations in the subsynchronous frequency band, which will be a key research point for my country's future large-scale long-distance transmission of new energy.

[0003] Currently, numerous regions have reported subsynchronous oscillation accidents caused by the interaction between wind power grid-connected systems and other power equipment, as well as with the power grid. To suppress subsynchronous oscillations between large-scale wind farm clusters and other devices, the shortcomings of existing mainstream analysis methods and technical solutions are as follows:

[0004] The method uses eigenvalue analysis to select the state variable with the highest sensitivity under subsynchronous oscillation, and then analyzes this parameter to understand the mechanism and characteristics of subsynchronous oscillation. The drawbacks of this method are: the process is cumbersome and computationally intensive; moreover, the accuracy of eigenvalue analysis is related to the accuracy of the system model, and if the system is large and the accuracy is insufficient, eigenvalue analysis will result in significant errors.

[0005] A small-signal model of the converter and other components of the new energy system is established in the frequency domain. The parameters of each controller are adjusted according to the grid impedance analysis method to improve the subsynchronous oscillation of the system. Its shortcomings are: for large systems, optimizing the parameters of each controller one by one is difficult to implement; and if the grid structure changes, subsequent maintenance becomes difficult.

[0006] Oscillation suppression is added to the control stage of the renewable energy converter, mainly including filtering, gain control, phase shifting, and limiting. However, its drawback is that the effect of adding damping suppressors is limited for subsynchronous oscillations with strong time-varying frequencies. Summary of the Invention

[0007] In response to novel power oscillations that differ from traditional subsynchronous oscillation mechanisms, this invention proposes a phase-shift-free subsynchronous damping control method and device based on a reactive power compensation device (SVG) to suppress subsynchronous oscillations.

[0008] To achieve the above objectives, the present invention provides a phase-shift-free subsynchronous damping control method based on SVG. This method adds a phase-shift-free subsynchronous damping controller to the inner current control loop of the SVG. The grid-side voltage at the grid connection point and the output of the outer loop voltage controller are used as inputs to the subsynchronous damping controller. The subsynchronous oscillation component of the grid-side voltage at the grid connection point and the output of the outer loop voltage controller are extracted by the subsynchronous damping controller. This subsynchronous oscillation component is then used as the output of the subsynchronous damping controller and superimposed onto the output of the inner current control loop of the SVG to obtain a modulation voltage component. This modulation voltage component is then input to the modulation loop of the SVG for control.

[0009] Furthermore, the subsynchronous damping controller implements the following steps:

[0010] Determine the oscillation angular frequency of each input component of the subsynchronous damping controller; based on the oscillation angular frequency of each input component, determine the transfer function of its corresponding second-order bandpass filter and establish a second-order bandpass filter model; based on the second-order bandpass filter model, select the gain of the proportional element. .

[0011] Furthermore, using the outputs of the grid-side voltage and outer loop voltage controller at the grid connection point as inputs to the subsynchronous damping controller includes the following steps:

[0012] Step 1: Calculate the difference between the actual DC side voltage and the actual AC side voltage of the SVG converter and their reference values. After passing the difference through a PI circuit, obtain the reference values ​​of the SVG current on the d-axis and q-axis.

[0013] Step 2: Decompose the d-axis reference value and q-axis reference value into positive and negative order to obtain the positive and negative components of the d-axis reference value and the positive and negative components of the q-axis reference value; decompose the d-axis and q-axis components of the grid-side voltage at the SVG grid connection point into positive and negative order to obtain the positive and negative components of the d-axis and the positive and negative components of the q-axis of the grid-side voltage.

[0014] Furthermore, extracting the subsynchronous oscillation components of the grid-side voltage and the output of the outer loop voltage controller at the grid connection point through the subsynchronous damping controller includes the following steps:

[0015] Step 3: Input each input component into the subsynchronous damping controller to obtain the positive sequence subsynchronous component of the d-axis reference value and the positive sequence subsynchronous component of the q-axis reference value output by the corrected SVG voltage controller, the positive sequence subsynchronous component of the d-axis and the positive sequence subsynchronous component of the q-axis of the grid-side voltage at the grid-connected SVG, and the negative sequence subsynchronous component of the d-axis and the negative sequence subsynchronous component of the q-axis of the grid-connected SVG.

[0016] Furthermore, the subsynchronous oscillation component is used as the output of the subsynchronous damping controller and superimposed on the output of the inner current control loop of the SVG to obtain the modulated voltage component, including the following steps:

[0017] Step 4: Superimpose the d-axis and q-axis subsynchronous components onto the output of the SVG current inner loop control to obtain the d-axis component and q-axis component of the modulation voltage.

[0018] Furthermore, the process of inputting the modulated voltage component into the modulation stage of the SVG for control includes the following steps:

[0019] Step 5: Perform coordinate transformation on the d-axis component and q-axis component of the modulation voltage to obtain... Axial components and The axis component is input to the modulation stage of the SVG for control.

[0020] Furthermore, the oscillation angular frequency of each input component is determined through FFT analysis.

[0021] Furthermore, the minimum value that achieves the suppression effect under the worst operating conditions is taken as the gain. The final setting value.

[0022] A phase-shift-free subsynchronous damping control device based on SVG includes an outer-loop voltage controller and an inner-loop current controller connected to the outer-loop voltage controller. The outer-loop voltage controller includes a first adder and a first PI controller. The inner-loop current controller includes a second adder, a second PI controller, a third adder, and a subsynchronous damping controller. The output of the first adder is connected to the input of the first PI controller, the output of the first PI controller is connected to the input of the second adder, the output of the second adder is connected to the input of the second PI controller and the input of the subsynchronous damping controller, the input of the subsynchronous damping controller is also connected to the grid-side voltage output from the SVG grid, and the outputs of the second PI controller and the subsynchronous damping controller are both connected to the input of the third adder. The subsynchronous damping controller includes a second-order bandpass filter, a proportional element, and a limiting element connected in sequence.

[0023] Furthermore, the control device follows the steps of the method described above.

[0024] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0025] This invention differs from previous methods that only applied additional control to the renewable energy converter side. Instead, it applies additional damping control from the perspective of the reactive power compensation device (SVG), specifically to the inner current loop control of the SVG. Simultaneously, it introduces the voltage and current components during subsynchronous oscillations and extracts their oscillation frequency bands, fully considering the influence between each input component and the subsynchronous oscillation component. This effectively suppresses the system subsynchronous oscillation problem caused by the interaction between the renewable energy unit and the SVG. Furthermore, compared to traditional additional damping control, this invention uses voltage and current reference components that are precisely phased with the system subsynchronous current—namely, the SVG's current d-axis and q-axis reference values ​​and the grid-side voltage at the SVG's grid connection point. These can be directly output without a proportional phase-shifting stage, generating a resistance effect to offset the oscillating current and effectively dissipating the oscillation energy in the system.

[0026] This invention eliminates the phase-shifting stage, has a simple principle, low computational load, and is easy to implement. It is suitable for suppressing subsynchronous oscillations caused by the interaction between large-scale renewable energy power plants and SVG (Static Var Compensator). For subsynchronous oscillations with a small frequency variation range, the method of this invention adds a phase-shift-free additional subsynchronous damping control to the installed and operational SVG, offering an economic advantage of requiring no additional equipment and possessing practical engineering significance. Attached Figure Description

[0027] Figure 1 This is a block diagram of the SVG control with additional damping control involved in the method of the present invention;

[0028] Figure 2 This is a block diagram of the additional damping control under the method of the present invention;

[0029] Figure 3 A schematic diagram of the structure of the computer device provided by the present invention;

[0030] Figure 4a This is a comparison chart of the effective value waveform of the 220kV bus voltage with and without additional damping control when the interaction between the doubly fed wind turbine and the SVG causes subsynchronous oscillation in PSCAD.

[0031] Figure 4b This is a comparison chart of the output power and grid connection point voltage waveforms of a doubly fed wind turbine and an SVG interacting to induce subsynchronous oscillations in PSCAD, with and without additional damping control.

[0032] Figure 5aThis is a comparison of the effective waveform of the 220kV bus voltage under the method of this invention and the additional damping control method of the traditional phase-shifting stage when the interaction between the doubly fed wind turbine and the SVG causes subsynchronous oscillation in PSCAD.

[0033] Figure 5b This is a comparison of the output power of the doubly fed wind turbine and the voltage waveform at the grid connection point when the interaction between the doubly fed wind turbine and the SVG causes subsynchronous oscillation in PSCAD, under the method of this invention and the additional damping control method of the traditional phase-shifting stage. Detailed Implementation

[0034] To make the objectives and technical solutions of this invention clearer and easier to understand, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0035] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] This invention utilizes the grid-side voltage and current components at the point where subsynchronous oscillation occurs due to interaction as additional subsynchronous damping control inputs for the SVG. After filtering, a certain damping effect is generated, and subsynchronous current is injected into the system to counteract the oscillation energy in the system, thereby achieving the purpose of suppressing subsynchronous oscillation.

[0037] The SVG is connected to the line in parallel through a transformer. Its overall control strategy includes a basic control strategy and a damped control (SSDC) strategy to suppress subsynchronous oscillations.

[0038] Example 1

[0039] For reference Figure 1 A phase-shift-free subsynchronous damping control device based on SVG includes an outer-loop voltage controller and an inner-loop current controller connected to the outer-loop voltage controller. The outer-loop voltage controller includes a first adder and a first PI controller; the inner-loop current controller includes a second adder, a second PI controller, a third adder, and a subsynchronous damping controller. The output of the first adder is connected to the input of the first PI controller; the output of the first PI controller is connected to the inputs of the second adder and the subsynchronous damping controller; the output of the second adder is connected to the input of the second PI controller; and the outputs of the second PI controller and the subsynchronous damping controller are both connected to the input of the third adder.

[0040] Figure 1 middle, This is the reference value for the DC-side voltage of the SVG converter; This is the actual value; This is the reference value for the AC side voltage; This is the actual value; and These are the reference values ​​for the SVG current on the dq axis, respectively; and These are the feedback values ​​of the SVG current on the dq axis, respectively; and These are the dq-axis components of the SVG access point voltage, respectively. This is a decoupling term applied to the active and reactive power of SVG; and These are the dq-axis components of the modulation voltage generated by the dual-loop control, respectively. and The modulation voltage generated by the dual-loop control is respectively Axial components.

[0041] Damped control SSDC strategy for suppressing subsynchronous oscillations, such as Figure 2 As shown. Figure 2 middle, , These are the positive and negative d-axis components of the SVG voltage controller output, respectively. , These are the positive and negative q-axis components of the SVG voltage controller output, respectively. , These represent the positive and negative d-axis components of the grid-side voltage at the SVG grid connection point; , These represent the positive and negative q-axis components of the grid-side voltage at the SVG grid connection point; , , , , , These are the secondary synchronization components of the corresponding signals via SSDC.

[0042] Example 2

[0043] Reference Figure 2 The present invention proposes an SVG-based subsynchronous damping controller without phase shift, the structure of which includes a second-order Butterworth bandpass filter, a proportional element and a limiting element connected in sequence.

[0044] A SVG-based subsynchronous damping control method without phase shifting has the following main steps:

[0045] Step 1: Set the DC-side voltage reference value of the SVG converter AC side voltage reference value of SVG converter And collect the actual DC side voltage of the SVG converter. AC side of SVG converter After passing through a PI circuit, the voltage-controlled output is obtained, and this output is used as the reference value of the SVG current on the d-axis. and q-axis reference value .

[0046] Step 2: Use the d-axis reference value obtained in Step 1. Performing positive and negative decomposition, the positive and negative components of the d-axis reference value are obtained as follows: , The result obtained in step 1 Performing positive and negative decomposition, the positive and negative components of the q-axis reference value are obtained as follows: , .

[0047] The grid-side voltage Us at the SVG grid connection point is collected, and its d-axis and q-axis components are decomposed into positive and negative d-axis components. , q-axis positive and negative components , .

[0048] Step 3: Obtain the oscillation angular frequency of each positive and negative sequence component from Step 2 through FFT analysis. This ensures that the additional damping control only works during subsynchronous oscillations;

[0049] Step 4: Calculate the oscillation angular frequency of each component obtained in Step 3. Substitute into formula 1 in step (4) A second-order bandpass filter model is established.

[0050] The second-order Butterworth bandpass filter has a transfer function as shown in Equation 1.

[0051] (1)

[0052] ,by ,in, , Let the upper and lower limit angular frequencies be different. The secondary synchronous oscillation frequency is taken as... For example, generally , , corresponding Take respectively and ; , corresponding Take respectively and ; , corresponding Take respectively and ;because , corresponding Since both are 0, these two components are no longer considered in subsequent steps.

[0053] Step 5: Based on the second-order bandpass filter model established in Step 4, select the gain of the proportional element. The subsynchronous damping controller was determined. Since the actual operating conditions of the system are highly variable, and the oscillations vary under different conditions, the minimum gain that achieves suppression under the worst operating condition was selected as the gain. The final setting value is generally taken as a value. . , Corresponding gain Take values ​​of 1 and 1.2 respectively; , , , corresponding Take 1.05.

[0054] Step 6: Take the components obtained in Step 4 , , , , , The input proportional circuit is fed into the output limiting circuit to obtain the corrected d-axis positive sequence synchronization component of the SVG voltage controller output. The corrected SVG voltage controller output q-axis positive sequence synchronization component The corrected SVG grid-side voltage d-axis positive sequence synchronous component The corrected SVG grid-side voltage q-axis positive sequence synchronization component at the grid connection point The corrected grid-side voltage d-axis negative sequence synchronization component at the SVG grid connection point The corrected SVG grid-side voltage q-axis negative sequence synchronization component .

[0055] Since the aforementioned components are at a certain angle to the phase of the system's subsynchronous current, they can produce a resistance effect to a certain extent. Therefore, the three-phase subsynchronous current that can cancel the oscillation current can be directly output without going through a phase-shifting stage, effectively dissipating the oscillation energy in the system.

[0056] Step 7: Superimpose the d-axis and q-axis subsynchronous components obtained in Step 6 onto the output of the SVG current inner loop control, that is, onto the original reference value of the SVG current on the d-axis. SVG current reference value on the q-axis Feedback value of SVG current on the d-axis Feedback value of SVG current on the q-axis d-axis component of SVG access point voltage q-axis component of SVG access point voltage Decoupling terms applied to active and reactive power in SVG The output of the SVG current inner loop control is superimposed respectively. , , , , , This forms the d-axis component of the modulation voltage. and the q-axis component of the modulation voltage .

[0057] Step 8: Convert the d-axis and q-axis components of the modulation voltage obtained in Step 7. and Perform coordinate transformations to obtain the following results: Axial components and Axial components The input is fed into the modulation stage of the SVG.

[0058] The method of this invention improves upon the original additional damping suppressor by eliminating the phase shifting stage, simplifying the process and reducing the computational load. It also has a good suppression effect on subsynchronous oscillations caused by the interaction between the phase-locked loop and the reactive power compensation device.

[0059] Example 3

[0060] The present invention provides a computer device, such as... Figure 3 As shown, it includes a memory and a processor that are electrically connected, wherein the memory stores a computer program that can run on the processor, and when the processor executes the computer program, it implements the steps of the above-described SVG-based non-phase-shifted additional subsynchronous damping control method.

[0061] The computer program can be divided into one or more modules / units, which are stored in the memory and executed by the processor to complete the present invention.

[0062] The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0063] The memory can be used to store the computer program and / or module. The processor realizes various functions of the low voltage ride-through reactive current control device / terminal equipment under weak grid by running or executing the computer program and / or module stored in the memory and calling the data stored in the memory.

[0064] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0065] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0066] To verify the method of this invention, a large-scale renewable energy cluster was built using the simulation platform PSCAD / EMTDC, with a focus on the model of the doubly-fed induction generator (DFIG) wind farm and the SVG reactive power compensation device. Frequency analysis of the subsynchronous component was performed using the FFT function in MATLAB, and the simulation results are shown below. Figure 4a and Figure 4b As shown, this is a comparison of the effective waveform of the 220kV bus voltage with and without additional damping control when the phase-locked loop and SVG interact in a 500MW doubly-fed wind farm group, causing subsynchronous oscillation. Figure 4a and Figure 4b It can be seen that when the parameters of the doubly fed wind turbine phase-locked loop are large, and the interaction with the reactive power compensation device SVG causes the phenomenon of subsynchronous oscillation in the system, the addition of subsynchronous oscillation control SSDC to the SVG in this invention can significantly suppress the subsynchronous oscillation of the system, and will not affect the dynamic reactive power compensation capability of the SVG.

[0067] Figure 5a and Figure 5b This chart compares the RMS waveform of the 220kV bus voltage under two control methods: a phase-locked loop (PLL) based on SVG with no additional phase-shift damping, and a traditional control method with additional damping and phase-shifting, when a subsynchronous oscillation occurs due to the interaction between the PLL and SVG in a 500MW doubly-fed wind farm. Figure 5a and Figure 5b It can be seen that, compared with the traditional additional damping control strategy with phase shifting element, the phase-shift-free additional subsynchronous damping control method based on SVG proposed in this invention uses both voltage and current as reference quantities to extract the oscillation frequency band components. After processing, these components are sent to the modulation stage of SVG, which can achieve a more significant suppression effect on subsynchronous oscillation.

[0068] According to existing research, the subsynchronous oscillations caused by wind farm grid connection can be classified into three types based on the different interacting objects: subsynchronous resonance, subsynchronous oscillations caused by devices, and subsynchronous control interaction. The oscillation studied by the method of this invention belongs to subsynchronous control interaction. Its main reason is that the doubly-fed induction generator (DFIG) has negative damping characteristics at the subsynchronous frequency, which increases the risk of subsynchronous oscillations.

[0069] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A SVG-based subsynchronous damping control method without phase shift, characterized in that, A subsynchronous damping controller without phase shifting is added to the inner current control loop of the SVG. The grid-side voltage at the grid connection point and the output of the outer loop voltage controller are used as the inputs of the subsynchronous damping controller. The subsynchronous oscillation component of the grid-side voltage at the grid connection point and the output of the outer loop voltage controller are extracted by the subsynchronous damping controller. The subsynchronous oscillation component is used as the output of the subsynchronous damping controller and superimposed on the output of the inner current control loop of the SVG to obtain the modulation voltage component. The modulation voltage component is then input to the modulation loop of the SVG for control.

2. The SVG-based subsynchronous damping control method without phase shift as described in claim 1, characterized in that, The subsynchronous damping controller implements the following steps: Determine the oscillation angular frequency of each input component of the subsynchronous damping controller; based on the oscillation angular frequency of each input component, determine the transfer function of its corresponding second-order bandpass filter and establish a second-order bandpass filter model; based on the second-order bandpass filter model, select the gain of the proportional element. .

3. The SVG-based subsynchronous damping control method without phase shift as described in claim 1, characterized in that, The method of using the outputs of the grid-side voltage and outer loop voltage controller at the grid connection point as the inputs of the subsynchronous damping controller includes the following steps: Step 1: Calculate the difference between the actual DC side voltage and the actual AC side voltage of the SVG converter and their reference values. After passing the difference through a PI circuit, obtain the reference values ​​of the SVG current on the d-axis and q-axis. Step 2: Decompose the d-axis reference value and q-axis reference value into positive and negative order to obtain the positive and negative components of the d-axis reference value and the positive and negative components of the q-axis reference value; decompose the d-axis and q-axis components of the grid-side voltage at the SVG grid connection point into positive and negative order to obtain the positive and negative components of the d-axis and the positive and negative components of the q-axis of the grid-side voltage.

4. The SVG-based subsynchronous damping control method without phase shift as described in claim 3, characterized in that, The extraction of the subsynchronous oscillation components of the grid-side voltage and the output of the outer loop voltage controller at the grid connection point through the subsynchronous damping controller includes the following steps: Step 3: Input each input component into the subsynchronous damping controller to obtain the positive sequence subsynchronous component of the d-axis reference value and the positive sequence subsynchronous component of the q-axis reference value output by the corrected SVG voltage controller, the positive sequence subsynchronous component of the d-axis and the positive sequence subsynchronous component of the q-axis of the grid-side voltage at the grid-connected SVG, and the negative sequence subsynchronous component of the d-axis and the negative sequence subsynchronous component of the q-axis of the grid-connected SVG.

5. The SVG-based subsynchronous damping control method without phase shift as described in claim 4, characterized in that, The step of using the subsynchronous oscillation component as the output of the subsynchronous damping controller and superimposing it on the output of the inner loop current control loop of the SVG to obtain the modulated voltage component includes the following steps: Step 4: Superimpose the d-axis and q-axis subsynchronous components onto the output of the SVG current inner loop control to obtain the d-axis component and q-axis component of the modulation voltage.

6. The SVG-based subsynchronous damping control method without phase shift as described in claim 5, characterized in that, The control of the modulation stage that inputs the modulation voltage component to the SVG includes the following steps: Step 5: Perform coordinate transformation on the d-axis component and q-axis component of the modulation voltage to obtain... Axial components and The axis component is input to the modulation stage of the SVG for control.

7. The SVG-based subsynchronous damping control method without phase shift as described in claim 2, characterized in that, The oscillation angular frequency of each input component is determined by FFT analysis.

8. The SVG-based subsynchronous damping control method without phase shift as described in claim 2, characterized in that, The minimum value that achieves the suppression effect under the worst operating conditions is taken as the gain. The final setting value.

9. A phase-shift-free subsynchronous damping control device based on SVG, characterized in that, The system includes an outer-loop voltage controller and an inner-loop current controller connected to the outer-loop voltage controller. The outer-loop voltage controller includes a first adder and a first PI controller. The inner-loop current controller includes a second adder, a second PI controller, a third adder, and a sub-synchronous damping controller. The output of the first adder is connected to the input of the first PI controller, and the output of the first PI controller is connected to the input of the second adder and the input of the sub-synchronous damping controller. The input of the sub-synchronous damping controller is also connected to the grid-side voltage output from the SVG grid. The output of the second adder is connected to the input of the second PI controller, and the outputs of the second PI controller and the sub-synchronous damping controller are both connected to the input of the third adder. The sub-synchronous damping controller includes a second-order bandpass filter, a proportional element, and a limiting element connected in sequence.

10. A SVG-based subsynchronous damping control device without phase shift as described in claim 9, wherein the control device implements the steps of the method described in any one of claims 1-8.

Images