Linear active disturbance rejection supplementary damping method and device for suppressing subsynchronous oscillation

Abstract

The present invention provides a linear self-disturbance rejection supplementary damping method and device for suppressing subsynchronous oscillations, including initializing the transmission line parameters and unit parameters; introducing LADRC on the rotor side and performing feedback control according to the state error; superimposing the output of the supplementary damping controller on the rotor side current loop to improve the positive damping of the control system; superimposing the disturbance on the rotor side current loop to suppress the subsynchronous oscillation of the doubly fed wind farm. In the rotor side inner loop control, the LESO with self-disturbance rejection control is used to estimate and feedback compensate the subsynchronous disturbance of the system in real time. The output of the supplementary damping controller is superimposed on the rotor side current loop to improve the positive damping of the control system to suppress low-frequency oscillations. It does not require complex parameter setting, has good anti-interference ability to changes in system operating conditions, and shows stronger robustness under high series compensation conditions with higher oscillation frequencies. It aims to solve the problem that doubly fed wind farms with series compensated transmission lines may aggravate subsynchronous oscillations of the power system.

Description

Technical Field

[0001] The present invention relates to the technical field of power system safety and stability control, and in particular to a linear auto-disturbance rejection supplementary damping method and device for suppressing subsynchronous oscillations. Background Art

[0002] Wind power plants are usually far away from the load center, and the scope of power consumption must be expanded through long-distance transmission. At present, doubly fed wind turbines have been widely used in the field of renewable energy power generation. Series compensation transmission technology can increase the capacity of transmission lines, but it can also cause sub-synchronous oscillations (SSO). In recent years, many SSO events have occurred in doubly fed wind farm grid-connected systems around the world, such as ERCOT power grid, Guyuan windfarm, and Oklahoma Gas & Electric. Studies have shown that such problems are mainly caused by the coupling between the doubly fed wind turbine converter control and the series compensation line, namely sub-synchronous control interaction (SSCI). If left unchecked, it will lead to power quality problems such as wind turbine disconnection and equipment damage. At present, common methods for suppressing sub-synchronous oscillations include: (1) Improving the damping of the system at the sub-synchronous oscillation frequency by changing the parameters of proportional integral (PI) control, but changing the control parameters may affect its original performance. For example, reducing the proportional coefficient of the RSC inner loop will cause the current tracking effect of the controller to decrease. (2) Replace the traditional PI controller with advanced nonlinear controllers such as partial feedback linearization controller, sliding mode control, H∞, etc. This type of nonlinear control relies on accurate modeling of wind turbines, and the parameters are difficult to adjust and the calculation is complex, making it difficult to implement in engineering. (3) Introduce supplementary sub-synchronous damping control (SSDC) in the stator-side or rotor-side converter control strategy to alleviate SSCI by reshaping the system impedance. However, when the system operating conditions change, the SSCI oscillation frequency shifts significantly, and the filter parameters and phase shift link parameters of SSDC must be re-adjusted. In addition, patent CN114123232B requires the use of expensive additional devices to suppress sub-synchronous oscillations, which is not economically feasible in actual engineering applications. Patents CN106981878B and CN105449699B require the NLSEF and ESO links in ADRC to be presented as nonlinear functions, with many parameters and complex adjustment methods. Patent CN115459300A requires the introduction of a high-pass filter in the LSEF of the linear anti-disturbance controller to improve the damping of the system in the oscillation frequency band, which increases the difficulty of controller design and fails to verify the SSCI suppression effect of the controller at a high series compensation level.

[0003] In view of this, this application is filed. Summary of the invention

[0004] The present invention provides a linear auto-disturbance rejection supplementary damping method and device for suppressing subsynchronous oscillation, which can at least partially improve the above-mentioned problem.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillations, comprising:

[0007] Obtaining a stator reactive power reference value, a stator reactive power actual value, a rotor side q-axis current actual value, and a disturbance suppression gain, and calling a preset first controller and a second controller to perform proportional integral processing on the stator reactive power reference value, the stator reactive power actual value, the rotor side q-axis current actual value, and the disturbance suppression gain to generate a third difference;

[0008] Obtaining an actual value of a rotor speed, a reference value of a rotor speed, an actual value of a d-axis current on a rotor side, and a disturbance suppression gain, and calling a preset third controller and a fourth controller to perform proportional-integral processing and linear auto-disturbance rejection combined with supplementary damping processing on the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain, to generate a sixth difference;

[0009] Performing coordinate conversion processing on the third difference and the sixth difference, converting the difference from dq coordinates to abc coordinates, and performing space vector pulse width modulation processing on the difference after coordinate conversion to obtain a space vector pulse width modulation result;

[0010] The machine-side converter RSC and the grid-side converter GSC are controlled according to the space vector pulse width modulation result.

[0011] The present invention also provides a linear active disturbance rejection supplementary damping device for suppressing subsynchronous oscillations, which comprises:

[0012] A proportional integral unit is used to obtain a stator reactive power reference value, a stator reactive power actual value, a rotor side q-axis current actual value and a disturbance suppression gain, and call a preset first controller and a second controller to perform proportional integral processing on the stator reactive power reference value, the stator reactive power actual value, the rotor side q-axis current actual value and the disturbance suppression gain to generate a third difference;

[0013] A disturbance suppression gain proportional integration unit is used to obtain the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain, and call the preset third controller and the fourth controller to perform proportional integration processing and linear auto-disturbance rejection combined with supplementary damping processing on the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain, so as to generate a sixth difference;

[0014] a conversion unit, configured to perform coordinate conversion processing on the third difference and the sixth difference, convert the difference from dq coordinates to abc coordinates, and perform space vector pulse width modulation processing on the difference after coordinate conversion to obtain a space vector pulse width modulation result;

[0015] The modulation unit is used to control the machine-side converter RSC and the grid-side converter GSC according to the space vector pulse width modulation result.

[0016] In summary, in view of the problem that the doubly-fed wind farm with series-compensated transmission lines may aggravate the subsynchronous oscillation of the power system, the linear auto-disturbance rejection supplementary damping method for suppressing subsynchronous oscillation is proposed. The method includes: initializing the transmission line parameters and unit parameters; introducing LADRC on the rotor side, and performing feedback control according to the state error; superimposing the output of the supplementary damping controller to the rotor side current loop to improve the positive damping of the control system; superimposing the disturbance on the rotor side current loop to suppress the subsynchronous oscillation of the doubly-fed wind farm. The linear auto-disturbance rejection supplementary damping method for suppressing subsynchronous oscillation uses the LESO of the auto-disturbance rejection control in the inner loop control of the rotor side to perform real-time estimation and feedback compensation of the subsynchronous disturbance of the system. Then, the output of the supplementary damping controller is superimposed on the rotor side current loop to improve the positive damping of the control system to suppress low-frequency oscillation. This method does not require complex parameter setting, has good anti-interference ability to changes in system operating conditions, and exhibits stronger robustness under high series compensation conditions with higher oscillation frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flow chart of a linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillations provided by a first embodiment of the present invention;

[0018] Figure 2 is a structural diagram of a DFIG wind farm grid-connected system provided by an embodiment of the present invention;

[0019] Figure 3 It is a schematic diagram of the SDC-LADRC structure provided by an embodiment of the present invention;

[0020] Figure 4 is a structural diagram of a supplementary damping controller provided by an embodiment of the present invention;

[0021] Figure 5 is a LADRC control block diagram provided by an embodiment of the present invention;

[0022] FIG6 (a) is a schematic diagram of the stator current of a DFIG under PI control provided by an embodiment of the present invention;

[0023] FIG6 (b) is a schematic diagram of the stator current of the DFIG under the SDC-LADRC provided in an embodiment of the present invention;

[0024] Figure 7 is a comparison diagram of the operating effects of three types of controls under different series compensation degrees provided by an embodiment of the present invention, Figure 7 (a) is a comparison diagram of PI, SSDC and SDC-LADRC at 40% series compensation. Figure 7 (b) is a comparison diagram of PI, SSDC and SDC-LADRC at 50% series compensation. Figure 7 (c) is a comparison diagram of PI, SSDC and SDC-LADRC at 60% series compensation. Figure 7 (d) is a comparison diagram of PI, SSDC and SDC-LADRC at 80% series compensation degree;

[0025] Figure 8 is a comparison diagram of the operating effects of SDC-LADRC and LADRC provided in an embodiment of the present invention, Figure 8 (a) is a comparison diagram of LADRC and SDC-LADRC at 40% series compensation. Figure 8 (b) is a comparison diagram of LADRC and SDC-LADRC at 50% series compensation. Figure 8 (c) is a comparison diagram of LADRC and SDC-LADRC at 60% series compensation degree;

[0026] Fig. 9 is a comparison diagram of the inhibition range of three SSCI methods provided by an embodiment of the present invention;

[0027] Fig.10 is a dynamic response test diagram provided by an embodiment of the present invention;

[0028] Fig.11 This is a comparison diagram of active waveforms of four control strategies under 50% series compensation provided by an embodiment of the present invention;

[0029] Fig.12 It is a module schematic diagram of a linear active disturbance rejection supplementary damping device for suppressing subsynchronous oscillations provided by the second embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] refer to Figure 1As shown, the first embodiment of the present invention discloses a linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillations, which can be executed by a linear active disturbance rejection supplementary damping device for suppressing subsynchronous oscillations (hereinafter referred to as a damping device), and in particular, executed by one or more processors in the damping device to implement the following method:

[0032] S1, obtaining a stator reactive power reference value, a stator reactive power actual value, a rotor side q-axis current actual value, and a disturbance suppression gain, and calling a preset first controller and a second controller to perform proportional integral processing on the stator reactive power reference value, the stator reactive power actual value, the rotor side q-axis current actual value, and the disturbance suppression gain to generate a third difference;

[0033] Specifically, step S1 includes: obtaining a stator reactive power reference value and stator reactive power actual value , and the stator reactive power reference value and stator reactive power actual value Performing difference processing to obtain a first difference value;

[0034] A preset first controller is used to perform proportional integration processing on the first difference to obtain a reference value of the d-axis component of the rotor current , wherein the first controller is a reactive power control outer loop;

[0035] Get the actual value of the q-axis current on the rotor side , the actual value of the q-axis current on the rotor side , reference value of the d-axis component of the rotor current and the disturbance rejection gain of the inner loop Performing difference processing to obtain a second difference value;

[0036] Use the preset second controller to perform proportional integration processing on the second difference to obtain the output of the rotor voltage d axis , wherein the second controller is a current control inner loop;

[0037] The disturbance rejection gain of the inner loop and the rotor voltage d-axis output A difference processing is performed to obtain a third difference value.

[0038] S2, obtaining the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain, and calling the preset third controller and the fourth controller to perform proportional integral processing and linear auto-disturbance rejection combined with supplementary damping processing on the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain, to generate a sixth difference;

[0039] Specifically, step S2 includes: obtaining the actual value of the rotor speed and rotor speed reference , and the actual value of the rotor speed and rotor speed reference Performing a difference process to obtain a fourth difference value;

[0040] Calling a preset third controller to perform proportional integration processing on the fourth difference to obtain a reference value of the q-axis component of the rotor current , wherein the third controller is a speed control outer loop;

[0041] Get the actual value of the rotor side d-axis current , the actual value of the rotor side d-axis current , reference value of the q-axis component of the rotor current and the disturbance rejection gain of the inner loop Perform difference processing to obtain the fifth difference value ;

[0042] The fifth difference is controlled by a preset fourth controller. Perform linear anti-disturbance control combined with supplementary damping to obtain the output of the rotor voltage q axis , wherein the fourth controller is a current control inner loop;

[0043] The disturbance rejection gain of the inner loop and the rotor voltage q-axis output A difference processing is performed to obtain a sixth difference value.

[0044] The fifth difference is controlled by a preset fourth controller. Perform linear auto-disturbance rejection combined with supplementary damping processing, specifically:

[0045] Call the ADRC to the five difference values Perform preprocessing, specifically:

[0046] For the five differences and the actual value of the q-axis current on the rotor side Estimated value of Perform difference processing to obtain the error , where the actual value of the rotor side q-axis current is Estimated value of The initial value of is 0;

[0047] The error Input to the linear error feedback controller LSEF for linear combination to obtain the intermediate variable ;

[0048] The intermediate variable and total disturbance Estimated value of Make a difference and convert the intermediate variable and total disturbance Estimated value of The difference is multiplied by , and obtain the intermediate variable when no disturbance is introduced ,in, To estimate the system gain, the total disturbance Estimated value of The initial value of is 0;

[0049] The intermediate variable when no disturbance is introduced Subsynchronous disturbances caused by external factors Add them and use the transfer function G(s) to calculate the addition result to get the actual value of the q-axis current on the rotor side ;

[0050] The intermediate variable when no disturbance is introduced and estimated system gain Multiply the product by the actual value of the rotor side q-axis current Input into the linear extended state observer LESO to update the actual value of the rotor side q-axis current Estimated value of and the total disturbance Estimated value of The value of

[0051] Get the actual power of the wind farm , calling the preset supplementary damping controller SDC to the actual power of the wind farm Perform supplementary preprocessing to generate compensation for the output of the supplementary damping link , wherein the supplementary preprocessing includes gain processing, phase shift processing, filtering processing and limiting processing;

[0052] The compensation amount output by the supplementary damping link and the actual value of the rotor side q-axis current Add them together to get the output of the rotor voltage q axis .

[0053] The mathematical expression of the active disturbance rejection controller is:

[0054] The active disturbance rejection controller is abstracted into a first-order differential equation, and the formula is: , where u is the control rate, , y is the system output, and the value of y is equal to the q-axis rotor voltage , t is the time-varying state;

[0055] Select state variables separately , h, transform the first-order differential equation into a state space equation, the formula is: , where, to facilitate matrix operations, the system output y is defined as the state variable , further, the state variable The q-axis rotor voltage output by the system , state variables is the total disturbance , the state variable h is the estimated value of the total disturbance , and They are and The derivative of , , , , .

[0056] The mathematical expression of the linear extended state observer LESO is: ,in, and for and The derivative of is the estimated value of the system output, z is the output of LESO, and These are LADRC dynamic performance parameters.

[0057] Intermediate variables The expression is: ,in, is the controller bandwidth.

[0058] The control rate Substitution In the formula, we can get , is the derivative of y. At this time, the system is simplified to a single integral system, and LSEF can be set as an intermediate variable The expression is: , for proportional control.

[0059] Transfer function G of control rate u c The formula for (s) is , where s is the Laplace operator, is the observer bandwidth. G(s) is the controlled object. Since LADRC is a model-free controller and does not rely on the precise mathematical model of the system, G(s) is not shown.

[0060] Among them, the advantages of model-free control include: 1. No detailed system model is required, which is suitable for systems that are difficult to accurately model or have high modeling costs; 2. Flexibility, able to cope with changes in system parameters, and has strong adaptability; 3. Less computing resource requirements, especially in complex systems, avoiding the high computing resources required to solve complex mathematical models.

[0061] See also Figures 2 to 5 In this embodiment, the devices involved in the linear anti-disturbance supplementary damping method for suppressing subsynchronous oscillations include a double-fed wind farm grid-connected system via a series compensation line, a double-fed induction generator, a rotor-side converter, a grid-side converter, a speed reactive loop, a voltage and current loop, a linear anti-disturbance control system, and a supplementary damping control system. Among them, the double-fed wind farm grid-connected system via a series compensation line consists of 67 double-fed wind turbines, each of which has a rated voltage of 0.575kv and a capacity of 1.5MW. The wind turbine is stepped up by a transformer and transmitted over long distances through a 161kv series compensation transmission line.

[0062] Initialize the transmission line parameters and unit parameters, such as Figure 2 The figure shows the schematic diagram of DFIG wind farm connected to the grid via series compensation transmission line. line , L line , C line They are the equivalent reactance, equivalent inductance and equivalent capacitance of the 161kV transmission line respectively.

[0063] See also Figure 3 The rotor side d-axis realizes the stator reactive power Q through two PI controllers s The first controller is the reactive power control outer loop, and the reference value i of the rotor current d-axis component is obtained through the proportional-integral link. rdref ; The second controller is the current control inner loop, and the d-axis component of the rotor voltage is obtained through the proportional-integral link. Similarly, the rotor side q-axis realizes the rotor speed through the PI controller and SDC-LADRC controller The third controller is the speed control outer loop, and the reference value i of the q-axis component of the rotor current is obtained through the proportional-integral link. rqref Controller 4 is the current control inner loop (in which the anti-disturbance control controller is embedded). The rotor voltage q-axis component u is obtained through the linear anti-disturbance control proposed by this method combined with the supplementary damping control link. rq .in, Figure 3 K p1 , K i1 , respectively represent the proportional gain and integral gain of controller 1, i.e. the first controller. Similarly, K p2 , K i2 , K p3 , Ki3 , are the proportional gain and integral gain of controller 2 and controller 3, and the parameters are generally adjusted through experiments and empirical formulas. K dr represents the disturbance suppression gain of the inner loop. This parameter determines the inner loop controller's ability to suppress disturbances. Increasing K dr It can improve the system's ability to resist disturbances, but it should also be noted that K dr If it is too large, the inner loop may respond too quickly, causing system instability or overshoot.

[0064] Among them, LADRC hopes to compensate the system to a simple series integral type. Any part that does not conform to the integral type will be regarded as a disturbance. No matter how the total disturbance changes, the compensated system can be effectively controlled. This allows LADRC to control the same type of objects with a similar time scale without changing parameters, which is very suitable for SSCI problems with time-varying oscillation frequencies.

[0065] will i rqref Connect to the linear active disturbance rejection control system, replace the original current inner loop proportional integral control, and send the output signal of the linear active disturbance rejection system to the LESO for analysis; that is, the first-order active disturbance rejection control system, replace the original proportional integral control of the rotor side current inner loop with a first-order active disturbance rejection controller. Send the output signal of the first-order active disturbance rejection system to LESO for analysis, and obtain the estimated value z1 of the output signal and the total disturbance z2. The expected difference is subtracted from z1 to obtain the error e1. The error e1 is sent to LSEF for linear combination to obtain the uncompensated control signal, and then subtracted from the product of z2 and the constant coefficient b0 to obtain the control signal and send it to the control object.

[0066] Among them, the active disturbance rejection controller module is specifically:

[0067] The control system is abstracted into a first-order differential equation in the form of , where b0 is the estimated system gain, f d is the total disturbance. The subsynchronous disturbance d caused by the system output and external factors is q , the estimation error of the time-varying state t and b0, etc. are included in the total disturbance. Select the state variable and transform the differential equation into the state space equation, as shown in the following formula: The linear extended state observer is expressed as follows: , where ^ represents the estimated value, the output z of LESO will track x, z1 is the estimate of irq, and z2 is the total disturbance f d , β1 and β2 are the dynamic performance parameters of LADRC.

[0068] Determine the control rate of the designed controller and express it by the following formula: LESF is represented by the following formula: ,in, is the controller bandwidth, u0 is the given reference variable of the system.

[0069] The transfer function is specifically: ,in, is the observer bandwidth, and the empirical formula for observer design is: .

[0070] G(s) is the controlled object. Since LADRC is a model-free controller and does not rely on the precise mathematical model of the system, G(s) is not displayed.

[0071] S3, performing coordinate conversion processing on the third difference and the sixth difference, converting the difference from dq coordinates to abc coordinates, and performing space vector pulse width modulation processing on the difference after coordinate conversion to obtain a space vector pulse width modulation result;

[0072] See also Figure 4 Specifically, in this embodiment, the supplementary damping controller is mainly composed of a gain, a phase shift link, a filter link and a limit link. The input end extracts the actual value P of the wind farm active power measured locally s , the output q-axis rotor voltage is compensated through gain, phase compensation, bandpass filter and limiting link, which can minimize the impact of SDC on the wind turbine mechanical system. Therefore, it involves neither communication link nor transmission delay. Compared with more complex model predictive control, linear quadratic Gaussian control, etc., the structure of this lead-lag module is simpler and easier to adjust. That is, the actual value P of the wind farm active power measured locally is extracted at the input of the supplementary damping controller s , after gain, phase compensation, bandpass filter and limiting links, the q-axis rotor voltage at the output end is compensated.

[0073] Gain module, adjusts the input signal amplitude to a suitable size through the amplifier, K s This is the amplifier's gain factor, K s The value of K should be within a reasonable range. s If the value of K is too small, the controller may not have a significant control effect and insufficient control capability. s If the value of K is too large, it may lead to over-control and over-amplify some signal noise, affecting the steady-state operation of the system. s A value that allows the SDC to provide adequate damping to the system.

[0074] The phase shifting link generally uses two identical lead-lag modules to achieve phase adjustment from -90° to +90°. Figure 4T1 and T2 are the time constants of lead and lag respectively, s is the Laplace operator, and the values ​​of T1 and T2 determine the magnitude of phase adjustment. Further, the residual method is used to set the parameters of SDC, and the subsynchronous characteristic value of the residual Ri is set to , the eigenvalue is moved 180 degrees to the left half plane to increase its damping ratio, so the phase compensation angle is selected , the specific parameters are calculated as follows: , where T1 and T2 are the time constants of lead and lag respectively, and the number of lead and lag modules is m, usually m=2. Where (arg(Ri) refers to the residual of Ri, which is the difference between the actual observed value and the model predicted value; the residual can be expressed as arg=actual value-predicted value; and are the real and imaginary parts of the subsynchronous eigenvalue, respectively, and j represents the imaginary unit; is a variable, obtained from the third formula above ( ). The specific parameters are shown in Table 2.

[0075] The filtering step needs to use a bandpass filter to extract the subsynchronous component at the subsynchronous oscillation frequency in the input signal. The transfer function of the second-order bandpass filter used is: ,in, is the damping coefficient, , f0 is the center frequency. f0 is usually the frequency of the subsynchronous oscillation, and It is related to the bandwidth B of the filter, and the relationship is The bandwidth of the bandpass filter is usually around 5Hz to ensure the filtering effect while adapting to possible frequency changes. f0 is usually the frequency of the subsynchronous oscillation, and It is related to the bandwidth B of the filter, and the relationship is The bandwidth of the bandpass filter is usually around 5Hz to ensure the filtering effect while adapting to possible frequency changes. The value of .

[0076] The limiter limits the amplitude of the SDC output signal through the limiter. Since the normal operation of the system may be threatened by sudden disturbances or failures, the control target deviates greatly from the reference value, resulting in a sudden increase in the controller output amplitude. Therefore, the controller output needs to be limited to a safe range. max , u min The value of u needs to comprehensively consider the controller performance and the impact on normal control functions. max , u min The value is set to 10% of the output of the control link to which the SDC is attached.

[0077] S4, controlling the generator-side converter RSC and the grid-side converter GSC according to the space vector pulse width modulation result.

[0078] Specifically, in this embodiment, the linear auto-disturbance rejection supplementary damping method for suppressing subsynchronous oscillations is used to establish a double-fed wind farm grid-connected system via a series compensation line in MATLAB / Simulink, and the effectiveness of the designed linear auto-disturbance rejection supplementary damping method for suppressing subsynchronous oscillations is verified through time domain simulation. Figure 2 As shown in Figure 1, the doubly-fed wind farm consists of 67 doubly-fed wind turbines, each with a rated voltage of 0.575 kV and a capacity of 1.5 MW. The wind turbines are stepped up by transformers and transmitted over long distances through 161 kV series compensation transmission lines. The simulation parameters of the wind farm system are shown in Table 1, and the designed controller parameters are shown in Table 2.

[0079] Table 1

[0080]

[0081] Table 2

[0082]

[0083] This method indirectly changes the oscillation frequency by changing the compensation level of the series capacitor. As shown in Figure 6 (a) and Figure 6 (b), the initial wind speed is 9m / s during the time domain simulation verification, and a 50% series compensation level is connected at 2s. As shown in Figure 6 (b), under the action of SDC-LADRC, the oscillation component in the DFIG stator current is alleviated.

[0084] See also Figure 7 , Figure 7 Three control methods under different degrees of series compensation are demonstrated. Figure 7 (a) Figure 7 (b) Figure 7 (c) Figure 7 The four figures (d) in the figure correspond to the series compensation levels of 40%, 50%, 60%, and 80%, respectively. The SDC-LADRC proposed in this method, the traditional PI control, and the traditional subsynchronous damping control SSDC in the literature are compared. It can be seen that PI has oscillations at any compensation level. Figure 7 In (a), Figure 7(b) Under low and medium compensation levels, both SDC-LADRC and SSDC can converge after a period of oscillation. The proposed method is superior to the traditional SSDC with fixed parameters. With the continuous improvement of the compensation level, the conventional SSDC fixed parameters cannot match the output required by the subsynchronous oscillation frequency. The convergence time of the SSDC method in the literature increases sharply, and even fails to converge. The proposed SDC-LADRC power curve has a smaller oscillation amplitude, a faster convergence speed, and better damping performance.

[0085] See also Figure 8 , Figure 8 The effect comparison of LADRC and SDC-LADRC under three series compensation conditions of 40%, 50% and 60% is shown. Figure 8 (a) Figure 8 As can be seen from (b) in Figure 1, the oscillation is suppressed to varying degrees under the action of LADRC and SDC-LADRC. Figure 8 As shown in (c) in Figure 2, as the compensation degree increases further, the vibration reduction effect of LADRC becomes worse and the oscillation convergence time becomes longer. The power curve shows that SDC-LADRC has better damping performance.

[0086] The time domain simulation results show that under the control of this method, the wind farm power curve oscillates less, converges faster, and the controller parameters do not fail when the system conditions change, indicating that SDC-LADRC has good damping performance.

[0087] Fig. 9 The suppression range comparison of the three suppression methods is shown, where SSDC1 is the grid-side additional damping control and SSDC2 is the rotor-side additional damping control. It can be seen that the SDC-LADRC proposed in this method has a wider range of suppression capability, which is better than the traditional SSDC method.

[0088] In order to illustrate the effectiveness of the method of the present invention, an experimental platform was built on MT6020HIL and MT1050RCP for verification. The wind farm consists of 67 wind turbines, each with a rated voltage of 0.575kV and a capacity of 1.5MW. The wind turbines are driven by transformers and transmitted over long distances through 161kV series compensated transmission lines. Fig.10 As shown, Fig.10 The experimental waveform of the dynamic response of the output voltage of the doubly-fed wind farm on the same time scale is given. Under the traditional double-loop control, 40% series compensation is put into use, and the oscillation is obvious. Subsequently, the SDC-LADRC control proposed in the present invention is put into use, and the voltage recovers from an unstable state to a stable state.

[0089] Fig.11The active power waveforms of wind farms with four different control strategies under 50% series compensation are shown in the figure. The experimental results show that compared with PI control, the proposed control strategy is more suitable for doubly fed wind power generation systems with random output fluctuations and strong disturbance factors, and has good transient stability operation characteristics, which can effectively suppress the SSCI problem of doubly fed wind farms; unlike the traditional SSDC method, the proposed control strategy does not require complex parameter setting, and the suppression effect is not affected by the time-varying nature of the oscillation frequency, and has good adaptability to changing working conditions; when SSCI occurs, the SDC-LADRC oscillation is smaller, the convergence speed is faster, and the damping performance is better. In addition, the control strategy is not only applicable to doubly fed wind power systems, but can also be extended to other types of generator sets.

[0090] In summary, the linear auto-disturbance rejection supplementary damping method for suppressing subsynchronous oscillations calls the trained first-order auto-disturbance rejection control to replace the inner loop PI control of the doubly fed wind turbine rotor side current. Secondly, the output of the supplementary damping controller is compensated to the rotor side current loop, and the disturbance is superimposed on the rotor side current loop to suppress subsynchronous oscillations of the doubly fed wind farm.

[0091] Compared with the prior art, the linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillations can ensure that the SSCI suppression strategy will not fail due to changes in system operating conditions. In addition, under high series compensation conditions, it is significantly better than the LADRC control method alone. Finally, the effectiveness of SDC-LADRC in suppressing subsynchronous oscillations was verified by time domain simulation.

[0092] See also Fig.12 A second embodiment of the present invention provides a linear active disturbance rejection supplementary damping device for suppressing subsynchronous oscillations, comprising:

[0093] A proportional-integral unit 201 is used to obtain a stator reactive power reference value, a stator reactive power actual value, a rotor-side q-axis current actual value, and a disturbance suppression gain, and call a preset first controller and a second controller to perform proportional-integral processing on the stator reactive power reference value, the stator reactive power actual value, the rotor-side q-axis current actual value, and the disturbance suppression gain to generate a third difference;

[0094] The disturbance suppression gain proportional integration unit 202 is used to obtain the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side and the disturbance suppression gain, and call the preset third controller and the fourth controller to perform proportional integration processing and linear auto-disturbance rejection combined with supplementary damping processing on the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side and the disturbance suppression gain to generate a sixth difference;

[0095] A conversion unit 203 is used to perform coordinate conversion processing on the third difference and the sixth difference, convert the difference from dq coordinates to abc coordinates, and perform space vector pulse width modulation processing on the difference after coordinate conversion to obtain a space vector pulse width modulation result;

[0096] The modulation unit 204 is used to control the generator-side converter RSC and the grid-side converter GSC according to the space vector pulse width modulation result.

[0097] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillations, characterized in that: include: Obtaining a stator reactive power reference value, a stator reactive power actual value, a rotor side q-axis current actual value, and a disturbance suppression gain, and calling a preset first controller and a second controller to perform proportional integral processing on the stator reactive power reference value, the stator reactive power actual value, the rotor side q-axis current actual value, and the disturbance suppression gain to generate a third difference; Obtaining an actual value of a rotor speed, a reference value of a rotor speed, an actual value of a d-axis current on a rotor side, and a disturbance suppression gain, and calling a preset third controller and a fourth controller to perform proportional-integral processing and linear auto-disturbance rejection combined with supplementary damping processing on the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain, to generate a sixth difference; Performing coordinate conversion processing on the third difference and the sixth difference, converting the difference from dq coordinates to abc coordinates, and performing space vector pulse width modulation processing on the difference after coordinate conversion to obtain a space vector pulse width modulation result; Controlling the machine-side converter RSC and the grid-side converter GSC according to the space vector pulse width modulation result; The actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain are obtained, and the preset third controller and the fourth controller are called to perform proportional integral processing and linear auto-disturbance rejection combined with supplementary damping processing on the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain to generate a sixth difference, which is specifically: Get the actual value of rotor speed and rotor speed reference , and the actual value of the rotor speed and rotor speed reference Performing a difference process to obtain a fourth difference value; Calling a preset third controller to perform proportional integration processing on the fourth difference to obtain a reference value of the q-axis component of the rotor current , wherein the third controller is a speed control outer loop; Get the actual value of the rotor side d-axis current , the actual value of the rotor side d-axis current , reference value of the q-axis component of the rotor current and the disturbance rejection gain of the inner loop Perform difference processing to obtain the fifth difference value ; The fifth difference is controlled by a preset fourth controller. Perform linear anti-disturbance control combined with supplementary damping to obtain the output of the rotor voltage q axis , wherein the fourth controller is a current control inner loop; The disturbance rejection gain of the inner loop and the rotor voltage q-axis output A difference processing is performed to obtain a sixth difference value.

2. The linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillation according to claim 1, characterized in that: The stator reactive power reference value, the stator reactive power actual value, the rotor side q-axis current actual value and the disturbance suppression gain are obtained, and the preset first controller and the second controller are called to perform proportional integral processing on the stator reactive power reference value, the stator reactive power actual value, the rotor side q-axis current actual value and the disturbance suppression gain to generate a third difference, specifically: Get stator reactive power reference value and stator reactive power actual value , and the stator reactive power reference value and stator reactive power actual value Performing difference processing to obtain a first difference value; A preset first controller is used to perform proportional integration processing on the first difference to obtain a reference value of the d-axis component of the rotor current , wherein the first controller is a reactive power control outer loop; Get the actual value of the q-axis current on the rotor side , the actual value of the q-axis current on the rotor side , reference value of the d-axis component of the rotor current and the disturbance rejection gain of the inner loop Performing difference processing to obtain a second difference value; Use the preset second controller to perform proportional integration processing on the second difference to obtain the output of the rotor voltage d axis , wherein the second controller is a current control inner loop; The disturbance rejection gain of the inner loop and the rotor voltage d-axis output A difference processing is performed to obtain a third difference value.

3. The linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillation according to claim 1, characterized in that: The fifth difference is controlled by a preset fourth controller. Perform linear auto-disturbance rejection combined with supplementary damping processing, specifically: Call the ADRC to the five difference values Perform preprocessing, specifically: For the five differences and the actual value of the q-axis current on the rotor side Estimated value of Perform difference processing to obtain the error , where the actual value of the rotor side q-axis current is Estimated value of The initial value of is 0; The error Input to the linear error feedback controller LSEF for linear combination to obtain the intermediate variable ; The intermediate variable and total disturbance Estimated value of Make a difference and convert the intermediate variable and total disturbance Estimated value of The difference is multiplied by , and obtain the intermediate variable when no disturbance is introduced ,in, To estimate the system gain, the total disturbance Estimated value of The initial value of is 0; The intermediate variable when no disturbance is introduced Subsynchronous disturbances caused by external factors Add them and use the transfer function G(s) to calculate the addition result to get the actual value of the q-axis current on the rotor side ; The intermediate variable when no disturbance is introduced and estimated system gain Multiply the product by the actual value of the rotor side q-axis current Input into the linear extended state observer LESO to update the actual value of the rotor side q-axis current Estimated value of and the total disturbance Estimated value of The value of Get the actual power of the wind farm , calling the preset supplementary damping controller SDC to the actual power of the wind farm Perform supplementary preprocessing to generate compensation for the output of the supplementary damping link , wherein the supplementary preprocessing includes gain processing, phase shift processing, filtering processing and limiting processing; The compensation amount output by the supplementary damping link and the actual value of the rotor side q-axis current Add them together to get the output of the rotor voltage q axis .

4. The linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillation according to claim 3, characterized in that: The mathematical expression of the active disturbance rejection controller is: The active disturbance rejection controller is abstracted into a first-order differential equation, and the formula is: , where u is the control rate, , y is the system output, and the value of y is equal to the q-axis rotor voltage , t is the time-varying state; Select state variables separately , h, transform the first-order differential equation into a state space equation, the formula is: , where the system output y is defined as the state variable , state variables The q-axis rotor voltage output by the system , state variables is the total disturbance , the state variable h is the estimated value of the total disturbance , and They are and The derivative of , , , , .

5. The linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillation according to claim 4, characterized in that: The mathematical expression of the linear extended state observer LESO is: ,in, and for and The derivative of is the estimated value of the system output, z is the output of LESO, and These are LADRC dynamic performance parameters.

6. The linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillation according to claim 3, characterized in that: Intermediate variables The expression is: ,in, is the controller bandwidth.

7. The linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillation according to claim 3, characterized in that: Control rate Substitution In the formula ,in, is the derivative of y, and LSEF is set as the intermediate variable The expression is: , to achieve proportional control.

8. The linear active disturbance rejection supplementary damping method for suppressing subsynchronous oscillation according to claim 3, characterized in that: The transfer function G c The formula for (s) is , where s is the Laplace operator, is the observer bandwidth.

9. A linear active disturbance rejection supplementary damping device for suppressing subsynchronous oscillations, characterized in that: include: A proportional integral unit is used to obtain a stator reactive power reference value, a stator reactive power actual value, a rotor side q-axis current actual value and a disturbance suppression gain, and call a preset first controller and a second controller to perform proportional integral processing on the stator reactive power reference value, the stator reactive power actual value, the rotor side q-axis current actual value and the disturbance suppression gain to generate a third difference; A disturbance suppression gain proportional integration unit is used to obtain the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain, and call the preset third controller and the fourth controller to perform proportional integration processing and linear auto-disturbance rejection combined with supplementary damping processing on the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain, so as to generate a sixth difference; a conversion unit, configured to perform coordinate conversion processing on the third difference and the sixth difference, convert the difference from dq coordinates to abc coordinates, and perform space vector pulse width modulation processing on the difference after coordinate conversion to obtain a space vector pulse width modulation result; A modulation unit, used for controlling the machine-side converter RSC and the grid-side converter GSC according to the space vector pulse width modulation result; The actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain are obtained, and the preset third controller and the fourth controller are called to perform proportional integral processing and linear auto-disturbance rejection combined with supplementary damping processing on the actual value of the rotor speed, the reference value of the rotor speed, the actual value of the d-axis current on the rotor side, and the disturbance suppression gain to generate a sixth difference, which is specifically: Get the actual value of rotor speed and rotor speed reference , and the actual value of the rotor speed and rotor speed reference Performing a difference process to obtain a fourth difference value; Calling a preset third controller to perform proportional integration processing on the fourth difference to obtain a reference value of the q-axis component of the rotor current , wherein the third controller is a speed control outer loop; Get the actual value of the rotor side d-axis current , the actual value of the rotor side d-axis current , reference value of the q-axis component of the rotor current and the disturbance rejection gain of the inner loop Perform difference processing to obtain the fifth difference value ; The fifth difference is controlled by a preset fourth controller. Perform linear anti-disturbance control combined with supplementary damping to obtain the output of the rotor voltage q axis , wherein the fourth controller is a current control inner loop; The disturbance rejection gain of the inner loop and the rotor voltage q-axis output A difference processing is performed to obtain a sixth difference value.

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