Methods, devices, equipment and systems for series oscillation damping control in wind power plants

Abstract

This application relates to a method, apparatus, equipment, and system for series compensation oscillation damping control in wind power plants. The method includes: extracting a first dynamic small signal from a first relevant parameter causing oscillations during doubly-fed induction generator (DFIG) operation via a filter, and inputting the PID controller with the PID output as a first feedforward term; obtaining a virtual voltage corresponding to a second dynamic small signal based on a second relevant parameter causing subsynchronous oscillations, and injecting this virtual voltage as a second feedforward term into the rotor voltage controller; and extracting a third dynamic small signal from a third relevant parameter causing rotor current loop oscillations during DFIG operation via a POD, performing phase and amplitude compensation, and then injecting this third dynamic small signal as a third feedforward term into the rotor current controller. This addresses the problems of unsatisfactory subsynchronous oscillation suppression effects and poor adaptability to different series compensation degrees in weak power grids in existing solutions.

Description

Technical Field

[0001] This application relates to the field of wind power generation technology, and in particular to a method, device, equipment and system for series compensation oscillation damping control of wind power farms. Background Technology

[0002] New energy wind power plants are often located at the end of the grid and require series compensation devices to improve transmission capacity. The capacitive reactance of the series compensation device and the inductive reactance of the grid have a resonant frequency point. Doubly fed induction generators (DFIGs) are directly connected to the grid. The rotor's equivalent resistance is related to the slip frequency. In a positive-sequence grid, the rotor speed and the subsynchronous resonant frequency result in a negative subsynchronous slip rate, making the rotor's equivalent resistance negative. When the grid resistance and the sum of the stator and rotor equivalent resistances are negative, the series-compensated grid will experience insufficient damping, causing grid voltage resonance oscillations at the resonant frequency point. This can lead to unstable generator operation, generator power oscillations, or even control failure and grid disconnection.

[0003] Doubly fed induction generators (DFIGs) are directly coupled to the power grid. Grid oscillations cause subsynchronous and supersynchronous oscillations, and the stator and rotor are mutually coupled and induced, resulting in oscillations at multiple resonant frequencies in stator voltage, stator current, rotor voltage, and rotor current. The subsynchronous grid makes conventional control methods for DFIGs unsuitable. Inappropriate controllers lead to mechanical torsional vibration and oscillation divergence in the wind turbine, expanding the fault range and endangering the stable operation of the power grid. This results in non-convergent oscillations in grid voltage, grid frequency, and active and reactive power of the wind farm, exhibiting underdamped oscillation divergence characteristics.

[0004] Existing subsynchronous oscillation suppression schemes mainly include: subsynchronous voltage feedforward control compensation method, excitation current damping control, or stator current virtual resistance feedforward control method. The current schemes have the problem that feedforward control cannot accurately control the subsynchronous resonant current. In particular, the detection and identification methods for voltage and current components with multiple resonant frequencies are complex and difficult. The control coupling is complex, requiring the detection of all subsynchronous voltage and current frequency information. The selection of the corresponding subsynchronous controller and the design of control parameters are complex, and the adaptability to different series compensation degrees in weak power grids is poor. Summary of the Invention

[0005] The purpose of this application is to provide a method, device, equipment, and system for series compensation oscillation damping control of wind power plants, which solves the problems of existing systems that require the detection of all subsynchronous voltage, current, and frequency information, have complex subsynchronous controller selection and control parameter design, and have poor adaptability to different series compensation degrees in weak power grids.

[0006] In a first aspect, embodiments of this application provide a method for series compensation oscillation damping control in a wind power plant, the method comprising: The first relevant parameter that causes power oscillation during the operation of the doubly fed motor is processed by a filter to extract the corresponding first dynamic small signal and input to the PID. The output control quantity of the PID is then injected into the rotor voltage controller as the first feedforward term. Based on the second relevant parameter that causes subsynchronous oscillation during the operation of the doubly fed motor, the virtual voltage corresponding to the second dynamic small signal is obtained and then injected into the rotor voltage controller as the second feedforward term. The third relevant parameter that causes rotor current loop oscillation during the operation of the doubly fed motor is extracted as a third dynamic small signal by the damping controller POD, and after phase and amplitude compensation, the output of the POD is injected as the third feedforward term into the rotor current controller setpoint.

[0007] In one or more embodiments, the method further includes: Obtain the secondary synchronous slip voltage and secondary synchronous slip frequency during the operation of the doubly fed motor; The fourth feedforward term is obtained by multiplying the subsynchronous slip voltage, the subsynchronous slip frequency, and the stator-rotor turns ratio coefficient, and then injected into the output of the rotor current controller. The output of the rotor current controller is connected to the rotor voltage controller.

[0008] In one or more embodiments, the method further includes: The rotor voltage is obtained using the rotor voltage controller based on the first feedforward term, the second feedforward term, and the output of the rotor current controller. The rotor voltage includes the d-axis rotor voltage and the q-axis rotor voltage. The rotor voltage is input to the phase-locked loop (PLL). After phase and amplitude compensation of the power component of the first dynamic small signal, it is multiplied by the gain coefficient and fed into the angular frequency integrator of the PLL. The corresponding grid voltage angle is then calculated using the PLL.

[0009] In one or more embodiments, the second relevant parameter is the rotor current or the stator current.

[0010] In one or more embodiments, the second relevant parameter is the rotor current. Based on the second relevant parameter causing subsynchronous oscillation during the operation of the doubly-fed motor, a virtual voltage corresponding to the second dynamic small signal is obtained and injected as a second feedforward term into the rotor voltage controller, including: After the rotor current is processed by a POD filter for second dynamic small-signal extraction and phase compensation, it is multiplied by a gain coefficient to obtain the virtual voltage corresponding to the second dynamic small-signal, which is then injected into the rotor voltage controller as the second feedforward term; or Multiply the rotor current by the sum of the virtual resistance and virtual impedance to obtain the virtual voltage corresponding to the second dynamic small signal, which is then injected as the second feedforward term into the output of the rotor current controller, which is connected to the rotor voltage controller.

[0011] In one or more embodiments, the method further includes: The rotor voltage is obtained using the rotor voltage controller based on the first feedforward term, the second feedforward term, and the output of the rotor current controller. The rotor voltage includes the d-axis rotor voltage and the q-axis rotor voltage. The stator active power and reference active power are used as inputs to the power controller. The corresponding angular frequency changes are processed by an inertia unit and a filter, and then fed back to the power controller via a negative feedback loop. The rotor voltage is input to the phase-locked loop (PLL), and the output of the power controller is fed into the angular frequency integrator of the PLL. The corresponding grid voltage angle is calculated using the PLL.

[0012] In one or more embodiments, the filter is a washout filter, and the transfer function of the washout filter is: ; Wherein, S is the differential operator, and the... This is the set time constant.

[0013] In one or more embodiments, the first relevant parameter includes the stator active power P along the d-axis. fb Stator reactive power Q along the q-axis fb The rotor voltage controller includes a d-axis rotor voltage controller and a q-axis rotor voltage controller.

[0014] In one or more embodiments, the third relevant parameter includes the d-axis rotor positive sequence voltage and the q-axis rotor positive sequence voltage, and the rotor voltage controller includes a d-axis rotor voltage controller and a q-axis rotor voltage controller.

[0015] In one or more embodiments, the damping controller POD includes a gain unit with a gain factor K, a washout filter, and at least one phase compensator.

[0016] Secondly, embodiments of this application provide a series compensation oscillation damping control device for wind power plants, the device comprising: The power oscillation suppression module is used to extract the first dynamic small signal corresponding to the first relevant parameter that causes power oscillation during the operation of the doubly fed motor after filtering and input it into the PID. The output control quantity of the PID is then injected into the rotor voltage controller as the first feedforward term. The subsynchronous oscillation suppression module is used to obtain the virtual voltage corresponding to the second dynamic small signal based on the second relevant parameter that causes subsynchronous oscillation during the operation of the doubly fed motor, and then inject it into the rotor voltage controller as the second feedforward term. The current oscillation suppression module is used to extract the third relevant parameter that causes rotor current loop oscillation during the operation of the doubly fed motor, extract the third dynamic small signal through the damping controller POD, and after phase and amplitude compensation, inject the output of the POD as the third feedforward term into the rotor current controller setpoint.

[0017] Thirdly, another embodiment of this application provides a wind farm series compensation oscillation damping control device, including at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method described in the first aspect above.

[0018] Fourthly, another embodiment of this application provides a computer storage medium storing a computer program for causing a computer to perform the method described in the first aspect above.

[0019] Fifthly, another embodiment of this application also provides a wind power generation system, including: The wind power plant series compensation oscillation damping control device provided in the second aspect above; A doubly-fed motor is used to operate under the control of the series compensation oscillation damping control device in the wind farm.

[0020] This application's embodiments utilize filters and damping controllers, employing feedforward and negative feedback methods for rotor voltage control, to suppress power oscillations, subsynchronous oscillations, and rotor current loop oscillations. This addresses the shortcomings of existing solutions, such as unsatisfactory subsynchronous oscillation suppression, the need to collect and calculate large amounts of subsynchronous voltage, current, and frequency information, the complex process of extraction, the coupling effects of subsynchronous controller selection and control parameter design, and poor adaptability to changes in grid series compensation degree when switching different series compensation devices on weak power grid transmission lines.

[0021] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 A schematic flowchart of the wind power plant series compensation oscillation damping control method provided in the embodiments of this application; Figure 2 A schematic diagram of the software structure of the damping controller provided in the embodiments of this application; Figure 3 A schematic diagram illustrating the use of filters to process stator active power and stator reactive power in an embodiment of this application; Figure 4 This is a schematic diagram illustrating the use of POD to process rotor current in an embodiment of this application; Figure 5 This is a schematic diagram illustrating how the rotor current is multiplied by the virtual resistance and impedance to obtain the virtual voltage according to an embodiment of this application; Figure 6 This is a schematic diagram illustrating the use of POD to process stator current in an embodiment of this application; Figure 7 This is a schematic diagram illustrating how the rotor positive sequence voltage, after POD processing, is fed back to the given point of the rotor current inner loop via a negative feedback loop according to an embodiment of this application. Figure 8 A schematic diagram of a software structure for suppressing power angle oscillations provided in an embodiment of this application; Figure 9 A schematic diagram of another software structure for suppressing power angle oscillations provided in an embodiment of this application; Figure 10 This is a schematic diagram of the overall control of the series compensation oscillation damping control of a wind power plant provided in the embodiments of this application; Figure 11 The diagram shows the subsynchronization suppression waveforms corresponding to the control method of this application and the relevant technologies in the simulation comparison of the embodiments of this application. Figure 12 The simulation comparison diagram for the relevant technologies and controls in the embodiments of this application shows whether the power divergence generator set at the PCC point is disconnected from the grid when the series compensation degree is 85%. Figure 13 A schematic diagram of the structure of the wind power plant series compensation oscillation damping control device provided in the embodiments of this application; Figure 14 A schematic diagram of the structure of a wind power plant series compensation oscillation damping control device provided in the embodiments of this application. Detailed Implementation

[0024] To further illustrate the technical solutions provided in the embodiments of this application, a detailed description is provided below in conjunction with the accompanying drawings and specific implementation methods. Although the embodiments of this application provide method operation steps as shown in the following embodiments or drawings, more or fewer operation steps may be included in the method based on conventional or non-inventive effort. For steps that do not logically have a necessary causal relationship, the execution order of these steps is not limited to the execution order provided in the embodiments of this application. In actual processing or when the control device executes the method, it may be executed sequentially or in parallel according to the method shown in the embodiments or drawings.

[0025] Based on the study of series compensation oscillations and weak grid impedance characteristics in wind farm transmission networks, this application analyzes the small-signal model of doubly-fed wind turbines and adopts an active damping control scheme based on small-signal analysis to suppress the power oscillations of the doubly-fed generators. It can also contribute damping to the grid so that the grid voltage and grid frequency oscillations converge and return to a stable state.

[0026] See Figure 1 Here is a flowchart of a wind power plant series oscillation damping control method according to an embodiment of this application. The method includes: Step 101: The first relevant parameter that causes power oscillation during the operation of the doubly fed motor is processed by a filter to extract the corresponding first dynamic small signal and input it into the PID controller. The output control quantity of the PID controller is then injected into the rotor voltage controller as the first feedforward term. The function of the filter is to extract the first dynamic small signal that causes power oscillation from the first relevant parameter. The PID controller uses the first dynamic small signal as the control target to control the power oscillation. The output control quantity is determined according to the output of the filter and the control target. The output control quantity is injected into the rotor voltage controller as the first feedforward term, thereby suppressing power oscillation.

[0027] Step 102: Based on the second relevant parameters that cause subsynchronous oscillation during the operation of the doubly fed motor, obtain the virtual voltage corresponding to the second dynamic small signal, and then inject it into the rotor voltage controller as the second feedforward term. The virtual voltage corresponding to the second dynamic signal that causes subsynchronous oscillation is injected as a feedforward into the rotor voltage controller to suppress subsynchronous oscillation.

[0028] Step 103: The third relevant parameter that causes rotor current loop oscillation during the operation of the doubly fed motor is extracted as a third dynamic small signal by the damping controller POD, and after phase and amplitude compensation, the output of the POD is injected into the rotor current controller as a third feedforward term.

[0029] The aforementioned POD function is to extract the third dynamic small signal that causes rotor current loop oscillation from the third relevant parameter and feed it back to the rotor current controller setpoint, thereby suppressing rotor current loop oscillation.

[0030] This application's embodiments utilize filters and damping controllers, employing feedforward and negative feedback methods for rotor voltage control, which can suppress power oscillations, subsynchronous oscillations, and rotor current loop oscillations. This addresses the problems of unstable performance and complex solution schemes in existing wind power doubly-fed generator converters due to the switching of series compensation transmission devices at the grid end, leading to grid resonant oscillation control.

[0031] In one or more embodiments, the damping controller POD includes a gain unit with a gain coefficient K, a washout filter, and at least one phase compensator. It should be noted that the gain unit, washout filter, and at least one phase compensator are all software units.

[0032] The aforementioned POD implements dynamic small-signal filtering extraction and amplitude / phase compensation functions. Based on the small-signal frequency domain distribution analysis, the time constant of the washout filter is set. With a first- or second-order lead-lag phase compensator, set the time constants T1, T2, T3, and T4, and set the small-signal gain coefficient K and the input / output signal saturation limit values. The specific structure of the damping controller POD is as follows: Figure 2 As shown, one or two phase compensators can be designed according to requirements. The formula in the phase compensator block diagram is the transfer function of the phase compensator.

[0033] The filter mentioned in this embodiment is a washout filter, and the transfer function of the washout filter is: ; Wherein, S is the differential operator, and the... This is the set time constant.

[0034] In one or more embodiments, the first relevant parameter mentioned above includes the stator active power P along the d-axis. fb Stator reactive power Q along the q-axis fb The rotor voltage controller includes a d-axis rotor voltage controller and a q-axis rotor voltage controller. For example... Figure 3 As shown, for the stator active power P fbA washout filter is used to extract the dynamic small signal ΔP,SSR, which is then input to the corresponding PID negative feedback controller. The PID controller uses ΔP,SSR to obtain the corresponding output control quantity Vrd2,SSR. This output control quantity Vrd2,SSR is injected as the first feedforward term into the d-axis rotor voltage controller and added to the rotor voltage term output from the inner loop of the rotor current controller (i.e., the rotor voltage term output from the rotor current controller). For the stator reactive power Q... fb The dynamic small signal ΔQ,SSR is extracted using a washout filter and input to the corresponding PID negative feedback controller. The PID controller obtains the corresponding output control quantity Vrq2,SSR based on ΔQ,SSR. The output control quantity Vrq2,SSR is injected into the q-axis rotor voltage controller as the first feedforward term and added to the rotor voltage term output by the inner loop of the rotor current.

[0035] A PID controller can determine the control quantity in the following ways:

[0036] The above K p For proportionality coefficient, K i Integral coefficient K d Let S be the differential coefficient, S be the differential operator, and T be the differential coefficient. f is the time constant.

[0037] The second relevant parameter mentioned above can be any of the following: 1) Rotor current As an optional implementation, when the second relevant parameter is the rotor current, the virtual voltage corresponding to the second dynamic small signal is obtained based on the second relevant parameter that causes subsynchronous oscillation during the operation of the doubly-fed motor, and injected as the second feedforward term into the rotor voltage controller, including: After the rotor current is extracted and phase compensated by the POD for the second dynamic small signal, it is multiplied by the gain coefficient to obtain the virtual voltage corresponding to the second dynamic small signal, which is then injected into the rotor voltage controller as the second feedforward term.

[0038] The aforementioned rotor currents include the d-axis rotor current Ird,fb and the q-axis rotor current Irq,fb, as follows: Figure 4As shown, the rotor current Ird,fb is processed by the damping controller POD to extract the small current signal, and phase and amplitude compensation is performed. The virtual voltage Vrd1,SSR obtained by multiplying by the gain coefficient is injected as the second feedforward control term into the rotor voltage controller of the d-axis, and added to the rotor voltage term output by the inner loop of the rotor current. The rotor current Irq,fb is processed by the damping controller POD to extract the small current signal, and phase and amplitude compensation is performed. The virtual voltage Vrq1,SSR obtained by multiplying by the gain coefficient is injected as the dynamic feedforward control term into the rotor voltage control of the q-axis, and added to the rotor voltage term output by the inner loop of the rotor current.

[0039] As another optional implementation, when the second relevant parameter is the rotor current, the virtual voltage corresponding to the second dynamic small signal is obtained based on the second relevant parameter that causes subsynchronous oscillation during the operation of the doubly-fed motor, and injected as the second feedforward term into the rotor voltage controller, including: Multiplying the rotor current by the sum of the virtual resistance and virtual impedance yields the virtual voltage corresponding to the second dynamic small signal, which is then injected as the second feedforward term into the output of the rotor current controller, which is connected to the rotor voltage controller. Figure 5 As shown: the rotor current Ird,fb is compared with (virtual resistance R) virtual +virtual sensory resistance jωL virtual Multiplying the two signals together, the virtual voltage corresponding to the second dynamic small signal is fed into the output of the d-axis rotor current controller and added to the rotor voltage term at the output of the d-axis rotor current controller. The output of the d-axis rotor current controller is connected to the d-axis rotor voltage controller. The rotor current Irq,fb is then multiplied by (virtual resistance R). virtual +virtual sensory resistance jωL virtual Multiplying these two signals yields the virtual voltage corresponding to the second dynamic small signal, which is fed into the output of the q-axis rotor current controller and added to the rotor voltage term at the output of the q-axis rotor current controller.

[0040] 2) Stator current

[0041] As an optional implementation, when the second relevant parameter is the stator current, the virtual voltage corresponding to the second dynamic small signal is obtained based on the second relevant parameter that causes subsynchronous oscillation during the operation of the doubly-fed motor, including: After the stator current is extracted and phase compensated by the second dynamic small signal through the POD, it is multiplied by the gain coefficient to obtain the virtual voltage corresponding to the second dynamic small signal.

[0042] The aforementioned stator currents include the d-axis stator current Isd,fb and the q-axis stator current Isq,fb, as follows: Figure 6As shown, the stator current Isd,fb is extracted by the damping controller POD, and phase and amplitude compensation is performed. The resulting stator current small signal ΔIsd,SSR is multiplied by the gain and injected as the second feedforward control term into the output of the d-axis rotor current controller, which is added to the rotor voltage term output by the d-axis rotor current controller. The stator current Isq,fb is extracted by the damping controller POD, and phase and amplitude compensation is performed. The resulting ΔIsq,SSR is multiplied by the gain and injected as the dynamic feedforward control term into the output of the q-axis rotor current controller, which is added to the rotor voltage term output by the q-axis rotor current controller.

[0043] In one or more embodiments, the aforementioned third relevant parameter includes the d-axis rotor positive sequence voltage and the q-axis rotor positive sequence voltage, and the rotor voltage controller includes a d-axis rotor voltage controller and a q-axis rotor voltage controller.

[0044] Small signal extraction and phase compensation are performed on the rotor positive sequence voltage. A negative feedback loop is designed to feed back to the rotor current inner loop setpoint to suppress rotor current inner loop oscillation and accelerate current inner loop convergence.

[0045] Specific implementation as follows Figure 7 As shown, the d-axis rotor positive sequence voltage Vrd,con is processed by the damping controller POD for third dynamic small signal and phase compensation to obtain the q-axis small signal current value ΔIrd,SSR, which is fed back to the rotor current controller setpoint via a negative feedback loop; the q-axis rotor positive sequence voltage Vrq,con is processed by the damping controller POD for third dynamic small signal and phase compensation to obtain the q-axis small signal current value ΔIrq,SSR, which is fed back to the rotor current controller setpoint via a negative feedback loop.

[0046] Based on the solution provided in the above embodiments of this application, the grid-connected converter of the wind turbine doubly fed generator set adopts rotor current small signal filter extraction and phase compensation, and uses the output signal of the damping filter as a dynamic feedforward control term to inject the rotor voltage to suppress subsynchronous oscillation.

[0047] The stator active and reactive power are extracted and compensated by a filter. The PQ small signal output by the filter is passed through a PID negative feedback controller. The PID output control quantity is injected into the rotor control voltage as a feedforward term to achieve power oscillation suppression.

[0048] The rotor positive sequence voltage is extracted by a filter and multiplied by a gain coefficient by a compensator. This control signal is negatively fed back to the rotor current loop setpoint. After passing through the rotor current forward channel closed loop, rotor current loop oscillation suppression is achieved.

[0049] Based on the above steady-state control, this embodiment can also utilize a feedforward control method to inject the steady-state feedforward term of the subsynchronous rotor control voltage, calculated by multiplying the subsynchronous voltage and subsynchronous slip rate by the stator-rotor turns ratio, into the rotor control voltage for subsynchronous control. Specifically, this includes: Obtain the secondary synchronous slip voltage and secondary synchronous slip frequency during the operation of the doubly fed motor; The fourth feedforward term is obtained by multiplying the subsynchronous slip voltage, the subsynchronous slip frequency, and the stator-rotor turns ratio coefficient, and then injected into the output of the rotor current controller. The output of the rotor current controller is connected to the rotor voltage controller.

[0050] This application's embodiments calculate and identify the amplitude of the subsynchronous slip voltage. and subsynchronous slip frequency Calculate the rotor subsynchronous slip voltage As the subsynchronous steady-state feedforward part of the rotor voltage, it is multiplied by the rotor turns ratio coefficient. It is injected into the rotor voltage controller as the fourth feedforward term for subsynchronous control. The specific calculation formula is as follows:

[0051] Among them, R r L represents the rotor resistance. lr L represents the leakage inductance of the rotor. r L represents the self-inductance of the rotor. m ωSSR represents the mutual inductance of a doubly-fed induction generator. fr,mech represents the mechanical speed of the rotor.

[0052] Based on the above-mentioned steady-state control and vibration control, the embodiments of this application can further suppress the power angle vibration during the operation of the doubly fed motor, specifically by adopting any of the following suppression methods.

[0053] 1) Power Angle Oscillation Damping Suppression Method 1

[0054] The rotor voltage is obtained by using the rotor voltage controller based on the output of the first feedforward term, the second feedforward term, and the rotor current controller. The rotor voltage includes the d-axis rotor voltage and the q-axis rotor voltage. The rotor voltage is input to the phase-locked loop (PLL). After phase and amplitude compensation of the power component of the first dynamic small signal, it is multiplied by the gain coefficient and fed into the angular frequency integrator of the PLL. The corresponding power angle is then calculated using the PLL.

[0055] Based on the motor's oscillation equation, the power component ΔP,SSR of the first dynamic small signal is multiplied by a gain coefficient and fed into the angular frequency integrator of the phase-locked loop (PLL) to suppress power angle oscillations and contribute damping to the grid frequency oscillations. PLL damping compensator structure. Figure 8 as follows:

[0056] J represents the inertia coefficient, P ref Given the power, P e Represents electromagnetic power, D represents the damping coefficient, ω ref ω represents the reference angular frequency, ω0 represents the motor angular frequency, ω g Kω represents the grid angular frequency, and Kω represents the gain coefficient.

[0057] Figure 8 In the middle, V abc V represents the grid stator voltage of the doubly-fed induction generator. abc Positive sequence voltage is obtained by decomposing the voltage into positive and negative sequence components. and negative sequence voltage For positive sequence voltage and negative sequence voltage The q-axis voltage is obtained by performing a synchronous rotating coordinate system transformation. and d-axis voltage q-axis voltage The input is fed into a PI controller for phase-locked loop regulation, resulting in the angular frequency increment Δω, which is then input into the angular frequency integrator. Simultaneously, ω... ff The rated angular frequency feedforward value is represented by ΔP,SSR. Multiplying ΔP and SSR by the gain coefficient Kω and feeding them into the angular frequency integrator of the phase-locked loop (PLL) for superposition processing, the compensated grid voltage orientation angle is obtained. This angle is used as the synchronous rotating coordinate change angle, where θ represents the grid angle. r θ represents the electrical angle of the motor rotor. slip This represents the rotor slip electrical angle.

[0058] The power angle oscillation suppression method provided in this application embodiment uses stator power extracted by a filter and phase corrected, multiplied by a gain droop coefficient, and fed forward to a phase-locked loop angular frequency integrator, thereby suppressing the subsynchronous grid frequency power angle oscillation and effectively increasing system damping.

[0059] 2) Power Angle Oscillation Damping Suppression Method Two

[0060] The rotor voltage is obtained using the rotor voltage controller based on the first feedforward term, the second feedforward term, and the output of the rotor current controller. The rotor voltage includes the d-axis rotor voltage and the q-axis rotor voltage. The stator active power and reference active power are used as inputs to the power controller. The corresponding angular frequency changes are processed by an inertia unit and a filter, and then fed back to the power controller via a negative feedback loop. The rotor voltage is input to the phase-locked loop (PLL), and the output of the power controller is fed into the angular frequency integrator of the PLL. The corresponding grid voltage angle is calculated using the PLL.

[0061] like Figure 9 As shown, the stator active power P fb and reference active power P ref As the input to the power controller, the power error increment ΔP is input. The angular frequency increment Δω is obtained, where J is the inertia coefficient, S is the differential operator, and D is the damping coefficient. (See figure.) Represents the washout filter, multiplying Δω by D. g The input washout filter is then fed back into the phase-locked loop to achieve frequency oscillation damping. g This is the angular frequency deviation feedback gain coefficient.

[0062] The above-mentioned solution provided in this application can be applied to wind power generation systems, which include doubly-fed generators and converter systems. This application is based on the application scenario of doubly-fed converter grid connection in a weak grid at the end of the grid where the grid impedance is compensated by series capacitors, and the grid is unstable under subsynchronous and supersynchronous oscillation conditions.

[0063] like Figure 10 The diagram shown is a schematic representation of the series oscillation damping control method for wind power plants provided in this application embodiment. This control method mainly includes the control of d-axis and q-axis parameters. 1) d-axis parameter control For stator active power P fb The dynamic small signal ΔP,SSR is extracted using a washout filter and input to the corresponding PID negative feedback controller. The output control quantity of the PID is then fed forward to the rotor voltage controller of the d-axis.

[0064] Given the active power Pset and the stator active power P fb After subtraction, the given current Ird,set is obtained through PI and input to the inner loop of the rotor current on the d-axis. The rotor current Ird,fb is extracted as a small current signal by the damping controller POD, and its phase and amplitude are compensated. The signal is then multiplied by the gain coefficient and fed forward to the rotor voltage controller on the d-axis. The rotor positive sequence voltage Vrd,con of the d-axis is subjected to third dynamic small signal and phase compensation by the damping controller POD to obtain ΔIrd,SSR, which is then fed back to the inner loop setpoint of the rotor current of the d-axis through the negative feedback loop. The given current Ird,set, rotor current Ird,fb, and ΔIrd,SSR fed back from the negative feedback loop are superimposed to obtain the rotor current controller input error. This error is then passed through a PI regulator and superimposed with the rotor subsynchronous slip voltage Vrd,ffc,SSR of the d-axis and a coupling term to obtain the rotor positive sequence voltage Vrd,con of the d-axis. This error is then output to the rotor voltage controller of the d-axis. The rotor voltage controller obtains the final rotor voltage of the d-axis based on the first feedforward term, the second feedforward term, and the rotor positive sequence voltage Vrd,con of the d-axis.

[0065] 2) Parameter control of the q-axis

[0066] For stator reactive power Q fb The dynamic small signal ΔQ,SSR is extracted using a washout filter and input into a PID negative feedback controller, which feeds the output control quantity of the PID forward to the rotor voltage controller of the q-axis. Given reactive power Qset and stator reactive power Q fb After subtraction, the given current Irq,set is obtained by the PI controller and input to the inner loop of the rotor current on the q-axis. The rotor current Irq,fb is extracted as a small current signal by the damping controller POD, and its phase and amplitude are compensated. The signal is then multiplied by the gain coefficient and fed forward to the rotor voltage controller of the q-axis.

[0067] The positive sequence voltage Vrq,con of the q-axis rotor is subjected to third dynamic small signal and phase compensation by the damping controller POD to obtain ΔIrq,SSR, which is then fed back to the inner loop setpoint of the q-axis rotor current through the negative feedback loop. The given current Irq,set, the rotor current Irq,fb, and the negative feedback loop are fed back. The input error of the rotor current controller is obtained by subtraction. It is then passed through a PI regulator and superimposed with the rotor subsynchronous slip voltage Vrq,ffc,SSR of the q-axis and the coupling term to obtain the rotor positive sequence voltage Vrq,con of the q-axis. This is output to the rotor voltage controller of the q-axis. The rotor voltage controller obtains the final rotor voltage of the q-axis based on the first feedforward term, the second feedforward term and the rotor positive sequence voltage Vrq,con of the q-axis.

[0068] The purpose of this application is to address the problems of unstable performance and complex solution schemes in the control of grid resonance oscillation caused by the switching of series compensation transmission devices at the grid end of existing wind power doubly-fed generator converters. The wind power grid series compensation oscillation damping control method provided in this application employs an oscillation component filter based on a small-signal model and an active damping controller. This damping controller must select active power, reactive power, and rotor current as control inputs. The control point injected into the damping controller output is the rotor current loop output, i.e., the rotor voltage synchronous coordinate system output point. Simultaneously, the damping control of the active power small signal must be injected into the phase-locked loop integrator for phase compensation and power angle damping. Furthermore, the positive-sequence rotor voltage small signal is negatively fed back into the rotor current loop's given input point, enabling the inner current loop to quickly enter a stable state. The combined effect of the small signal extraction and feedforward / feedback methods solves the problems of series compensation resonance and doubly-fed generator oscillation suppression in weak grids, contributing damping and stabilizing the grid. This overcomes the poor adaptability of wind power applications in weak grids with subsynchronous oscillations, thereby significantly expanding and improving the control performance of wind power grid-connected converters. For the negative sequence subsynchronous frequency component, its negative sequence equivalent resistance is always positive and will not cause the damping effect of the negative voltage group, so the influence of the negative sequence can be ignored. By default, this application uses positive sequence power and positive sequence voltage and current for signal processing and oscillation control.

[0069] The control scheme of this application was verified in the PSCAD simulation software environment for wind farm and power grid models. The PSCAD power grid model was built according to the actual structure and parameters of a 300MW wind farm power grid, and test cases were designed according to the actual operating state of the power grid. A sudden addition of a series compensation capacitor to the simulated power grid caused the wind turbine to enter a subsynchronous resonance state, which was used to verify and evaluate the performance of the doubly-fed induction generator (DFIG) wind turbine under these grid parameters. Simulation results show that, using the subsynchronous damping oscillation suppression method of this application, the oscillations of the DFIG power, grid voltage, and grid frequency can converge quickly, allowing the wind farm to return to stable and continuous operation, with a power control accuracy error of less than 1%. Other subsynchronous oscillation control methods for DFIG converters can alleviate the power oscillation, but oscillations still occur, with a power oscillation error greater than 3%. The PSCAD simulation waveforms are shown below. Figure 11 As shown.

[0070] Controlling subsynchronous power grids with different series compensation levels (25%, 45%, 65%, 85%) was performed. Using the control method described in this application, the power grid quickly recovered from oscillations and returned to stable normal operation. Other subsynchronous oscillation control schemes were controllable at 25% series compensation, but as the series compensation increased to 45%, the doubly-fed induction generator could not stably control the wind turbine unit, causing it to rapidly diverge and disconnect from the grid, rendering it inoperable. (PSCAD simulation waveforms are shown.) Figure 12 .

[0071] Based on the same inventive concept, this application also provides a series compensation oscillation damping control device for wind power plants, such as... Figure 13 As shown, the device includes: The power oscillation suppression module 1301 is used to extract the first dynamic small signal corresponding to the first relevant parameter that causes power oscillation during the operation of the doubly fed motor after filtering and input it into the PID, and inject the output control quantity of the PID as the first feedforward term into the rotor voltage controller. The subsynchronous oscillation suppression module 1302 is used to obtain the virtual voltage corresponding to the second dynamic small signal based on the second relevant parameters that cause subsynchronous oscillation during the operation of the doubly fed motor, and then inject it into the rotor voltage controller as the second feedforward term. The current oscillation suppression module 1303 is used to extract the third relevant parameter that causes rotor current loop oscillation during the operation of the doubly fed motor, extract the third dynamic small signal through the damping controller POD, and after performing phase and amplitude compensation, inject the output of the POD as the third feedforward term into the rotor current controller setpoint.

[0072] In one or more embodiments, the device further includes: The steady-state feedforward module is used to obtain the subsynchronous slip voltage and subsynchronous slip frequency during the operation of the doubly fed motor; the subsynchronous slip voltage, subsynchronous slip frequency and stator-rotor turns ratio coefficient are multiplied to obtain a fourth feedforward term, which is injected into the output terminal of the rotor current controller, and the output terminal of the rotor current controller is connected to the rotor voltage controller.

[0073] In one or more embodiments, it further includes: The first power angle oscillation suppression module is used to obtain the rotor voltage based on the output of the rotor voltage controller, the first feedforward term, the second feedforward term, and the rotor current controller. The rotor voltage includes the d-axis rotor voltage and the q-axis rotor voltage. The rotor voltage is input to the phase-locked loop (PLL), and after phase and amplitude compensation of the power component of the first dynamic small signal, it is multiplied by the gain coefficient and fed into the angular frequency integrator of the PLL. The corresponding grid voltage angle is calculated using the PLL.

[0074] In one or more embodiments, the second relevant parameter is the rotor current or the stator current.

[0075] In one or more embodiments, the second relevant parameter is the rotor current. Based on the second relevant parameter causing subsynchronous oscillation during the operation of the doubly-fed motor, a virtual voltage corresponding to the second dynamic small signal is obtained and injected as a second feedforward term into the rotor voltage controller, including: After the rotor current is processed by a POD filter for second dynamic small-signal extraction and phase compensation, it is multiplied by a gain coefficient to obtain the virtual voltage corresponding to the second dynamic small-signal, which is then injected into the rotor voltage controller as the second feedforward term; or Multiply the rotor current by the sum of the virtual resistance and virtual impedance to obtain the virtual voltage corresponding to the second dynamic small signal, which is then injected as the second feedforward term into the output of the rotor current controller, which is connected to the rotor voltage controller.

[0076] In one or more embodiments, the device further includes: The second power angle oscillation suppression module is used to obtain the rotor voltage based on the first feedforward term, the second feedforward term, and the output of the rotor current controller using the rotor voltage controller. The rotor voltage includes the d-axis rotor voltage and the q-axis rotor voltage. The stator active power and the reference active power are used as inputs to the power controller. The obtained corresponding angular frequency change is processed by an inertia unit and a filter, and then fed back to the power controller via a negative feedback loop. The rotor voltage is input to the phase-locked loop (PLL), and the output of the power controller is fed into the angular frequency integrator of the PLL. The corresponding grid voltage angle is calculated using the PLL.

[0077] In one or more embodiments, the filter is a washout filter, and the transfer function of the washout filter is: ; Wherein, S is the differential operator, and the... This is the set time constant.

[0078] In one or more embodiments, the first relevant parameter includes the stator active power P along the d-axis. fb Stator reactive power Q along the Q axis fb The rotor voltage controller includes a d-axis rotor voltage controller and a q-axis rotor voltage controller.

[0079] In one or more embodiments, the third relevant parameter includes the d-axis rotor positive sequence voltage and the q-axis rotor positive sequence voltage, and the rotor voltage controller includes a d-axis rotor voltage controller and a q-axis rotor voltage controller.

[0080] In one or more embodiments, the damping controller POD includes a gain unit with a gain factor K, a washout filter, and at least one phase compensator.

[0081] After introducing the wind farm series oscillation damping control method and apparatus according to exemplary embodiments of this application, the wind farm series oscillation damping control device according to another exemplary embodiment of this application will be introduced next.

[0082] In some possible implementations, the wind farm series oscillation damping control device according to this application may include at least one processor and at least one memory. The memory stores program code that, when executed by the processor, causes the processor to perform the steps in the wind farm series oscillation damping control method according to the various exemplary embodiments of this application described above.

[0083] The following reference Figure 14 This application describes a series oscillation damping control device for a wind power plant according to this embodiment. Figure 14 The wind farm series compensation oscillation damping control device shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of this application.

[0084] like Figure 14 As shown, the series compensation oscillation damping control device for wind power plants is presented in the form of general-purpose electronic equipment. Components of the electronic equipment may include, but are not limited to, the aforementioned at least one processor 141 and the aforementioned at least one memory 142.

[0085] The memory 142 may include a readable medium in the form of volatile memory, such as random access memory (RAM) and / or cache memory, and may further include read-only memory (ROM).

[0086] The memory 142 may also include a program / utility having a set (at least one) of program modules, including but not limited to: an operating system, one or more application programs, other program modules, and program data, each or some combination of these examples may include an implementation of a network environment.

[0087] The wind farm series oscillation damping control device can also communicate with one or more external devices (such as keyboards, pointing devices, etc.), one or more devices that enable users to interact with the wind farm series oscillation damping control device, and / or any device that enables the wind farm series oscillation damping control device to communicate with one or more other electronic devices (such as routers, modems, etc.). This communication can be performed through an input / output (I / O) interface.

[0088] This application also provides a wind power generation system, including: The wind power plant series compensation oscillation damping control device provided in the above embodiments; A doubly-fed motor is used to operate under the control of the series compensation oscillation damping control equipment in the wind farm.

[0089] In some possible implementations, various aspects of the wind farm series oscillation damping control method provided in this application can also be implemented in the form of a program product, which includes program code. When the program product is run on a computer device, the program code is used to cause the computer device to perform the steps of the wind farm series oscillation damping control method according to the various exemplary embodiments of this application described above.

[0090] The program product may employ any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0091] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0092] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for series compensation oscillation damping control in a wind power plant, characterized in that, The method includes: The first relevant parameter that causes power oscillation during the operation of the doubly fed motor is processed by a filter to extract the corresponding first dynamic small signal and input to the proportional-integral-derivative (PID) control. The output control quantity of the PID is then injected into the rotor voltage controller as the first feedforward term. Based on the second relevant parameter that causes subsynchronous oscillation during the operation of the doubly fed motor, the virtual voltage corresponding to the second dynamic small signal is obtained and then injected into the rotor voltage controller as the second feedforward term. The third relevant parameter that causes rotor current loop oscillation during the operation of the doubly fed motor is extracted as a third dynamic small signal by the damping controller POD, and after phase and amplitude compensation, the output of the POD is injected as the third feedforward term into the rotor current controller setpoint.

2. The method according to claim 1, characterized in that, Also includes: Obtain the secondary synchronous slip voltage and secondary synchronous slip frequency during the operation of the doubly fed motor; The fourth feedforward term is obtained by multiplying the subsynchronous slip voltage, the subsynchronous slip frequency, and the stator-rotor turns ratio coefficient, and then injected into the output of the rotor current controller. The output of the rotor current controller is connected to the rotor voltage controller.

3. The method according to claim 1 or 2, characterized in that, Also includes: The rotor voltage is obtained using the rotor voltage controller based on the first feedforward term, the second feedforward term, and the output of the rotor current controller. The rotor voltage includes the d-axis rotor voltage and the q-axis rotor voltage. The rotor voltage is input to the phase-locked loop (PLL). After phase and amplitude compensation of the power component of the first dynamic small signal, it is multiplied by the gain coefficient and fed into the angular frequency integrator of the PLL. The corresponding grid voltage angle is then calculated using the PLL.

4. The method according to claim 1, characterized in that, The second relevant parameter is the rotor current or the stator current.

5. The method according to claim 4, characterized in that, The second relevant parameter is the rotor current. Based on the second relevant parameter that causes subsynchronous oscillation during the operation of the doubly-fed motor, the virtual voltage corresponding to the second dynamic small signal is obtained and injected into the rotor voltage controller as the second feedforward term, including: After the rotor current is processed by a POD filter for second dynamic small-signal extraction and phase compensation, it is multiplied by a gain coefficient to obtain the virtual voltage corresponding to the second dynamic small-signal, which is then injected into the rotor voltage controller as the second feedforward term; or Multiply the rotor current by the sum of the virtual resistance and virtual impedance to obtain the virtual voltage corresponding to the second dynamic small signal, which is then injected as the second feedforward term into the output of the rotor current controller, which is connected to the rotor voltage controller.

6. The method according to claim 1 or 2, characterized in that, Also includes: The rotor voltage is obtained using the rotor voltage controller based on the first feedforward term, the second feedforward term, and the output of the rotor current controller. The rotor voltage includes the d-axis rotor voltage and the q-axis rotor voltage. The stator active power and reference active power are used as inputs to the power controller. The corresponding angular frequency changes are processed by an inertia unit and a filter, and then fed back to the power controller via a negative feedback loop. The rotor voltage is input to the phase-locked loop (PLL), and the output of the power controller is fed into the angular frequency integrator of the PLL. The corresponding grid voltage angle is calculated using the PLL.

7. The method according to claim 1, characterized in that, The filter is a washout filter, and the transfer function of the washout filter is: ； Wherein, S is the differential operator, and the... This is the set time constant.

8. The method according to claim 1, characterized in that, The first relevant parameter includes the stator active power P along the d-axis. fb Stator reactive power Q along the q-axis fb The rotor voltage controller includes a d-axis rotor voltage controller and a q-axis rotor voltage controller.

9. The method according to claim 1, characterized in that, The third relevant parameter includes the d-axis rotor positive sequence voltage and the q-axis rotor positive sequence voltage, and the rotor voltage controller includes a d-axis rotor voltage controller and a q-axis rotor voltage controller.

10. The method according to claim 1 or 8, characterized in that, The damping controller POD includes a gain unit with a gain factor K, a washout filter, and at least one phase compensator.

11. A series compensation oscillation damping control device for a wind power plant, characterized in that, include: The power oscillation suppression module is used to extract the first dynamic small signal corresponding to the first relevant parameter that causes power oscillation during the operation of the doubly fed motor after filtering and input it into the PID. The output control quantity of the PID is then injected into the rotor voltage controller as the first feedforward term. The subsynchronous oscillation suppression module is used to obtain the virtual voltage corresponding to the second dynamic small signal based on the second relevant parameter that causes subsynchronous oscillation during the operation of the doubly fed motor, and then inject it into the rotor voltage controller as the second feedforward term. The current oscillation suppression module is used to extract the third relevant parameter that causes rotor current loop oscillation during the operation of the doubly fed motor, extract the third dynamic small signal through the damping controller POD, and after phase and amplitude compensation, inject the output of the POD as the third feedforward term into the rotor current controller setpoint.

12. A series compensation oscillation damping control device for a wind power plant, characterized in that, The method includes at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method as described in any one of claims 1-10.

13. A computer storage medium, characterized in that, The computer storage medium stores a computer program that enables the computer to perform the method as described in any one of claims 1-10.

14. A wind power generation system, characterized in that, include: The wind power plant series compensation oscillation damping control device as described in claim 11; A doubly-fed motor is used to operate under the control of the series compensation oscillation damping control device in the wind farm.

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