A broadband oscillation suppression method, terminal and dielectric for a flexible low-frequency power transmission system

Abstract

This invention relates to the field of flexible low-frequency AC transmission control technology, and discloses a broadband oscillation suppression method, terminal, and medium for flexible low-frequency transmission systems. Based on the M3C characteristics of the flexible low-frequency transmission system, this method designs a first-order L-ADRC model; constructs an ADRC-PI composite dual-closed-loop control strategy and configures the ADRC based on this strategy; uses a Gaussian quantum behavior particle swarm optimization algorithm to optimize the parameters of the ADRC controller; based on this strategy, oscillation discrimination of the flexible low-frequency transmission system is performed using dual parallel criteria in the frequency and time domains; and based on the discrimination results and combined with a pre-synchronous transition hybrid control strategy, the state of the ADRC controller in the flexible low-frequency transmission system is adjusted to achieve disturbance-free connection and oscillation suppression. This invention effectively suppresses broadband oscillations induced by various factors in the FLFT system and avoids the adverse effects of data noise on the system control performance.

Description

Technical Field

[0001] This invention relates to the field of flexible low-frequency AC power transmission control technology, specifically a broadband oscillation suppression method, terminal, and medium for a flexible low-frequency power transmission system. Background Technology

[0002] Flexible low-frequency AC transmission (FLFT) technology is a power transmission method that transmits power at frequencies lower than the power frequency (50 / 60Hz). It combines the advantages of power frequency AC systems (flexible networking and easy voltage transformation) with the long-distance transmission capacity of DC systems. It possesses unique technical and economic advantages in medium- and long-distance offshore wind power transmission scenarios, effectively complementing both power frequency AC and DC transmission. Its applications in long-distance power transmission, offshore wind power transmission, and urban power grids have been extensively studied. Currently, the AC / AC converters commonly used in FLFT systems are modular multilevel matrix converters (M3C) based on fully controlled power electronic devices. These converters employ decoupled control on the power / low-frequency side based on proportional-integral (PI) control, and a dual closed-loop control structure with inner and outer loops. This decoupled control... dq The control quantities along the coordinate axes exhibit good tracking performance. However, the increased number of bridge arms and the more complex power electronic structure complicate the inter-frequency energy coupling on both sides of the M3C. Wideband oscillations caused by various factors not only easily lead to voltage and current fluctuations resulting in a decline in power quality, but may also damage electrical equipment such as power generation equipment, transformers, converters, and user-side equipment. Furthermore, the large number of power electronic devices complicates the control structure of the FLFT system. Data noise caused by electromagnetic interference couples with the control quantities, negatively impacting the system's control performance and even causing serious problems such as FLFT system instability. Therefore, effectively suppressing oscillations and data noise in the FLFT system is particularly important.

[0003] Currently, most M3C systems use PI controllers, whose parameters cannot be flexibly adjusted in actual engineering. When the system oscillates or becomes unstable due to data disturbances, the parameters cannot be adaptively adjusted to maintain stable system operation. In addition, the research in "Study on the Subsynchronous Oscillation Characteristics Dominated by the Current Inner Loop of Direct-Drive Wind Farms under Low Operating Conditions" found that the parameter settings of the current inner loop PI controller are also one of the main inducing factors for grid oscillation.

[0004] Active disturbance rejection controller (ADRC), as an advanced control strategy, has been widely applied in various fields in recent years. Facing nonlinear, multivariable, strongly coupled systems and disturbance problems, it can effectively handle uncertainties, external disturbances, and nonlinearities in the system, improving the dynamic performance and robustness of the system. However, ADRC parameter tuning is complex and relies heavily on experience. Achieving efficient and optimal parameter configuration for ADRC controllers has always been an engineering challenge. Furthermore, when facing complex dynamic characteristics during temporary non-malicious operating conditions (such as FLFT system startup / grid connection processes, system reclosing, etc.), the extended state observer (ESO) of ADRC may struggle to quickly and accurately estimate system state variables, leading to poor dynamic performance, poor robustness, or even system instability. This limits the reliability of direct application of ADRC in power systems and further increases the difficulty of its controller parameter tuning. Summary of the Invention

[0005] To address the technical problem of poor suppression of broadband oscillations and data noise in existing technologies for flexible low-frequency AC transmission systems, this invention provides a broadband oscillation suppression method, terminal, and medium for flexible low-frequency transmission systems.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention discloses a method for suppressing broadband oscillations in a flexible low-frequency power transmission system, comprising the following steps:

[0008] S1. Based on the characteristics of the modular multilevel matrix converter (M3C) of the flexible low-frequency transmission system, a first-order L-ADRC model is designed. This model includes a linear extended state observer, a linear state error feedback law, and disturbance compensation.

[0009] S2. Construct an ADRC-PI composite dual closed-loop control strategy and configure ADRC for this strategy; wherein, the ADRC controller in this strategy is used for the outer loop voltage control of the low-frequency side of the M3C, which is completed by the first-order L-ADRC model, and the inner loop control of the low-frequency side of the M3C is completed by the PI controller.

[0010] S3. The ADRC controller is configured with optimal parameters using a Gaussian quantum behavior particle swarm optimization algorithm.

[0011] S4. Based on the ADRC-PI composite dual closed-loop control strategy, the oscillation of the flexible low-frequency transmission system is determined by dual parallel criteria in the frequency and time domains. According to the determination results and combined with the pre-synchronous transition hybrid control strategy, the state of the ADRC controller in the flexible low-frequency transmission system is adjusted to achieve disturbance-free connection and oscillation suppression.

[0012] This invention discloses a computer terminal, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the broadband oscillation suppression method for a flexible low-frequency power transmission system as described above.

[0013] The present invention also discloses a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the broadband oscillation suppression method for the flexible low-frequency power transmission system as described above.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1. The broadband oscillation suppression method for flexible low-frequency transmission systems disclosed in this invention selects a first-order L-ADRC based on the mathematical model order of the FLFT system and designs and constructs an ADRC-PI composite double closed-loop control structure, which effectively suppresses broadband oscillations induced by various factors in the FLFT system, while avoiding the adverse effects of data noise on the system control effect, and significantly improves the robustness and anti-interference capability of the system.

[0016] 2. This invention uses the GQPSO algorithm to... dq The outer-loop ADRC is used for controller parameter configuration, and the particle dimension, objective optimization function, particle swarm size, and maximum number of iterations are reasonably designed. Iterative updates of the particle swarm are performed under FLFT system oscillation and data noise disturbance conditions, solving the problems of high difficulty and low efficiency in manual parameter tuning. Meanwhile, GQPSO, through the Gaussian mutation operator, endows particles with the ability to jump with "low probability and large amplitude," solving the problem of traditional PSO algorithms easily getting trapped in local optima. This enables rapid and efficient configuration of multiple ADRC optimization parameters.

[0017] 3. The oscillation identification and suppression method designed in this invention judges the stability of the system based on the dual parallel criteria of time and frequency domain of multiple monitoring points, and realizes the ADRC without disturbance through HPSTC after the occurrence of oscillation / data noise disturbance conditions. This ensures accurate judgment and timely suppression of abnormal system conditions, and also avoids the system stability problem caused by the inaccuracy of LESO observation in ADRC due to temporary non-malicious conditions (such as FLFT system startup / grid connection process, reclosing, etc.), further improving the reliability of the system. Attached Figure Description

[0018] Figure 1 This is a structural diagram of the offshore wind power transmission system via FLFT in Embodiment 1 of the present invention.

[0019] Figure 2 This is a flowchart of the broadband oscillation suppression method for the flexible low-frequency power transmission system in Embodiment 1 of the present invention.

[0020] Figure 3 This is a structural diagram of the first-order L-ADRC model in Embodiment 1 of the present invention.

[0021] Figure 4 This is a block diagram of the improved M3C low-frequency side control structure based on oscillation suppression in Embodiment 1 of the present invention.

[0022] Figure 5 This is a flowchart of ADRC optimization parameter configuration based on GQPSO in Embodiment 1 of the present invention.

[0023] Figure 6 This is a comparison chart of the control effects of the ADRC-PI composite dual closed-loop control strategy and the traditional PI-PI dual closed-loop control strategy under the system oscillation condition in Embodiment 1 of the present invention.

[0024] Figure 7 This is a control effect diagram of the traditional inner-loop PI-outer-loop PI control strategy under data noise disturbance in Embodiment 1 of the present invention.

[0025] Figure 8 This is a control effect diagram of the ADRC-PI composite dual closed-loop control strategy under data noise disturbance in Embodiment 1 of the present invention.

[0026] Figure 9 The diagram shows the control effect of the ADRC-PI composite dual closed-loop control strategy (GQPSO parameter optimization configuration) in Embodiment 1 of the present invention under system oscillation conditions.

[0027] Figure 10 This is a diagram showing the control effect of the ADRC-PI composite dual closed-loop control strategy (manual parameter tuning) in Embodiment 1 of the present invention under system oscillation conditions.

[0028] Figure 11 This is a diagram showing the control effect of the traditional inner-loop PI-outer-loop PI control strategy in Embodiment 1 of the present invention under system oscillation conditions.

[0029] Figure 12 This is a schematic diagram of the computer terminal structure in Embodiment 2 of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] This embodiment is a simulation model of offshore wind power transmitted via flexible low-frequency transmission. Specifically, it includes the offshore wind turbine collection section, the low-frequency submarine cable transmission section, and the onshore converter station and grid connection section. The specific structure is as follows: Figure 1 As shown, Figure 1 In this context, WTG represents wind turbine generator set. k 1 and k 2 represents the turns ratio of the power frequency transformer and the turns ratio of the low frequency transformer, respectively. A simulation model of this embodiment was built using PSCAD / EMTDC and MATLAB co-simulation, and the relevant parameters are shown in Table 1. This embodiment focuses on improving the control strategy and structure of the M3C section of the onshore converter station to address the oscillation conditions and data noise interference problems that occur within the M3C.

[0033] Table 1: Simulation parameters of wind power transmission via flexible low-frequency transmission system

[0034] ;

[0035] Please see Figure 2 This embodiment provides a broadband oscillation suppression method for a flexible low-frequency power transmission system, including the following steps, namely S1 to S4.

[0036] S1. Based on the characteristics of the modular multilevel matrix converter (M3C) in flexible low-frequency transmission systems, design as follows: Figure 3 The first-order L-ADRC (Active Disturbance Rejection Controller) model shown includes a linear extended state observer, a linear state error feedback law, and disturbance compensation.

[0037] Step S1 includes the following specific steps, namely S11~S12.

[0038] S11. Construct the linear extended state observer (LESO), whose equation is:

[0039] ;

[0040] In the formula, e For the output state observations of LESO Compared with the actual output value of the system The difference, u For system input, This is the total system disturbance compensation coefficient. This represents the total disturbance observations; and They are respectively and The derivative; β 1 and β 2 represents the preset gain parameter for LESO. It should be noted that the systems mentioned in the subsequent methods of this embodiment are all flexible low-frequency power transmission systems.

[0041] S12. Construct the linear state error feedback law (LESF) and the disturbance compensation term. The specific equations are as follows:

[0042] ;

[0043] ;

[0044] ;

[0045] In the formula, For LESF input; Provides the ADRC output reference value; The proportional coefficient of ADRC is given; where LESF is equivalent to a proportional-integral cascade control, yielding the output value. u and the output value after disturbance compensation u 0.

[0046] S2. Construct an ADRC-PI composite dual closed-loop control strategy and configure ADRC for this strategy, such as... Figure 4 As shown, this strategy is applied to the low-frequency side control structure of M3C; wherein, the ADRC controller in this strategy is used for the outer loop voltage control of the low-frequency side of M3C, which is completed by the first-order L-ADRC model, and the inner loop control of the low-frequency side of M3C is completed by the PI controller.

[0047] Step S2 includes the following specific steps, namely S21 to S26.

[0048] S21. Obtain the low-frequency three-phase voltage of the flexible low-frequency transmission system , and And through the Park transformation, the three-phase voltage is changed from abc Transformation to three-phase stationary coordinate system dq In a synchronously rotating coordinate system, the transformed three-phase voltage is obtained. dq Axial components and In this embodiment, the transformation formula is expressed as:

[0049] ;

[0050] In the formula, θ for a Phase voltage u la phase, sin θ cos θ They represent θ The sine and cosine values.

[0051] S22. Secondly, construct the control equations for the low-frequency side of the M3C:

[0052] ;

[0053] ;

[0054] In the formula, For the bridge arm inductor of M3C; For the three-phase current on the low-frequency side of the flexible low-frequency transmission system d Axial components; For the three-phase current on the low-frequency side of the flexible low-frequency transmission system q Axial components; t For time; The angular frequency of the flexible low-frequency power transmission system; For the common-mode voltage of the low-frequency side bridge arm d Axial components; For the common-mode voltage of the low-frequency side bridge arm q Axial component; M3C low-frequency side dq The given reference voltages for the shafts are denoted as follows: and The inner ring generated by the outer ring dq The shaft reference currents are respectively denoted as and .

[0055] S23. Replace the outer loop with an ADRC controller. dq A PI controller for the axis, denoted as dq Axis ADRC, input the outer loop and As respectively dq The control object of the axis ADRC is set with the outer loop input reference value. and They are respectively dq The control reference values ​​and output values ​​of the axis ADRC are respectively dq Inner loop current reference value and This yields an ADRC-PI composite dual-closed-loop control strategy with an outer loop based on ADRC control and an inner loop based on PI control; where, dq The control equations for the axis ADRC are as follows:

[0056] ;

[0057] In the formula, and They are respectively and The derivative; express d The total disturbance of the system caused by various known and unknown physical quantities of the axis; express q The total disturbance of the system caused by various known and unknown physical quantities of the axis; and These represent the low-frequency side of the flexible low-frequency transmission system. d shaft and q External disturbance to the shaft.

[0058] S24. Perform parameter design and configuration for the first-order L-ADRC model designed in step S1; where, for the linearly extended state observer LESO, according to the pole placement principle, let , ; For observer bandwidth; dq The observer equations for the outer loop are as follows:

[0059] d axis: ;

[0060] q axis: ;

[0061] In the formula, and They are respectively d Axis observer pair d Axis controlled object and disturbance quantity Observed values; and They are respectively and The derivative; for d The system gain estimate of the axis observer; for d The output of the axis observer; for d Axis observer bandwidth; and They are respectively q Axis observer pair q Axis controlled object and disturbance quantity Observed values; and They are respectively and The derivative; for q The system gain estimate of the axis observer; for q The output of the axis observer; for q Axis observer bandwidth; and They are respectively d shaft and q Reference value for the inner loop current of the shaft.

[0062] S25. Calculate the derivative from step S24. , , and Discrete observation data are obtained by approximating the differential formula. d Taking the LESO axis as an example, the specific formula is as follows:

[0063] ;

[0064] Based on this dq The differential equation of the axis observer with respect to the observations is transformed into an iterative update form, and the differential iteration formula is as follows:

[0065] ;

[0066] ;

[0067] In the formula, h Indicates the differential step size; and The first h +1 and h time The state value.

[0068] Based on the above differential iteration formula, set up the following in MATLAB programming: dq Initial value of LESO output for axis ADRC and And set the differential step size h The simulation step size was set to 50 μs, consistent with PSCAD / EMTDC; subsequently, data from the flexible low-frequency transmission system were read. , , and As input, and at the same time , , and As the output value, thus achieving dq The axis observer outputs updated observations.

[0069] S26. Construction dq The linear state error feedback law LESF of the axis ADRC and the disturbance compensation term are used to calculate the inner loop. dq Shaft reference current and The Extended State Observer (LESO) provides observations of system state variables. , Compared with a given reference value , Subtract to get the difference , Multiplying the linear state error feedback law LESF by the gain coefficient and subtracting the observed output value of LESO for the total system disturbance from the disturbance compensation term, we obtain the following results: dq The output of the axis ADRC is the reference value for the inner loop current control. , The output value expression is as follows:

[0070] ;

[0071] ;

[0072] In the formula, and They represent dq The controller bandwidth of the axis ADRC; for and The difference obtained by subtraction for and The difference obtained by subtraction; , , , , and These are all key parameters that need to be configured in the ADRC part of the ADRC-PI composite dual closed-loop control strategy. Parameter configuration directly affects the control performance of the FLFT system, such as robustness and dynamic response. It is important to emphasize that the parameters obtained through the above steps... dq The basic structure design and bandwidth of the ADRC shaft can be implemented through MATLAB programming, and linked with the FLFT system simulation model in PSCAD / EMTDC for simulation calculation, so as to realize the implementation and verification of the invention in specific embodiments.

[0073] S3. The ADRC controller is configured with optimal parameters using the Gaussian Quantum Behavior Particle Swarm Optimization (GQPSO) algorithm. This specifically includes the controller bandwidth. , Observer bandwidth , and system state estimates , Flowchart as follows Figure 5 As shown, the specific steps are as follows, namely S31~S36.

[0074] S31. Initialize the particle swarm:

[0075] The initial positions of the particles are randomly generated in the solution space using a uniform probability distribution. The particles are 6-dimensional, corresponding to the controller bandwidth. and Observer bandwidth and and system gain estimate and And set the particle population size N =80; where the expression for the value of each particle is:

[0076] ;

[0077] In the formula, Indicates the first i The value of each particle, 1≤ i ≤ N ; , , , , and All of these are ADRC parameters that need to be optimized; and They are respectively and The lower limit is set based on ADRC parameter configuration experience. , ; and They are respectively and The lower limit is generally set according to the ADRC parameter configuration principle. 3 to 5 times Therefore, it is set , ; and They are respectively and The lower limit of the system The error tolerance is generally around 30%, so the upper and lower limits are set relatively wide here. , ; This represents a random number between 0 and 1.

[0078] S32. Fitness Calculation and Evaluation:

[0079] Based on the requirements of flexible low-frequency power transmission systems, a multi-objective optimization function is defined, and the fitness of the parameters corresponding to each particle is calculated. , The smaller the value, the better the solution; among them, The expression is:

[0080] ;

[0081] In the formula, α , β and γ All are weighting factors, and this embodiment sets them as follows: α = 0.3, β = 0.3, γ = 0.4; Input M3C low-frequency side for ADRC controller dq The settling time of the flexible low-frequency transmission system behind the outer ring of the shaft reflects the dynamic stability of the system; ADRC output value y Compared with the output reference value Steady-state error between; The total perturbation reflecting the steady-state process of ADRC is expressed as:

[0082] ;

[0083] In the formula, Input M3C low-frequency side for ADRC controller dq Time after the outer ring of the shaft; for t The ADRC output value at time 1; it should be noted that the minimum requirement for generating a particle swarm is that at least one particle exists, making If the fitness is less than a preset minimum fitness (the minimum fitness in this embodiment is set to 4.8), and this requirement is not met, the process returns to step S31 to regenerate a new particle swarm.

[0084] S33. Calculate the global optimal position:

[0085] Global optimal position For all individual particles, the historical best position (Personal Best Position) Pbest The mean of the search, reflecting the statistically optimal direction of the group search, is expressed as:

[0086] ;

[0087] In the formula, Indicates the first i The optimal position of each individual particle.

[0088] S34. Update particle swarm positions:

[0089] Random numbers are generated using the absolute values ​​of a Gaussian probability distribution with zero mean and unit variance. Step sizes with high probability of small amplitude and low probability of high amplitude are then generated around the current point, causing the particle to move away from the current point and escape local minima. The particle's update position function is:

[0090] ;

[0091] In the formula, and They are respectively In the t and t The state value at time +1; The preset coefficient of shrinkage and expansion; G and k It is the absolute value of the generated value of the Gaussian probability distribution function with a mean of 0 and a variance of 1, denoted as and ; p The parameters are calculated and updated based on local and global optima, and the calculation equation is as follows: , For the first i The optimal position of each individual particle. The position of the particle with the best fitness in the entire population; The weighting factor is expressed as follows:

[0092] ;

[0093] in, m It is the absolute value of the generated value of the Gaussian probability distribution function with a mean of 0 and a variance of 1, denoted as .

[0094] S35. Fitness Optimization Update:

[0095] Individual fitness optimization: if particles i fitness Then update ; For particles i The fitness is calculated from the individual's optimal position.

[0096] Population fitness optimization: if particlesi fitness Then update ; The fitness is calculated for the position of the particle with the best fitness in the entire population.

[0097] S36. Repeated iterative loop:

[0098] Repeat steps S32 to S35 until any of the following stopping conditions are met:

[0099] (1) The fitness value reaches the preset accuracy ( );Pick ;

[0100] (2) Reaching the maximum number of iterations T =500.

[0101] Output Information on each component of the particle , , , , and .

[0102] S4. Based on the ADRC-PI composite dual closed-loop control strategy, the oscillation of the flexible low-frequency transmission system is determined by dual parallel criteria in the frequency and time domains. According to the determination results and combined with the pre-synchronous transition hybrid control strategy, the state of the ADRC controller in the flexible low-frequency transmission system is adjusted to achieve disturbance-free connection and oscillation suppression.

[0103] like Figure 4 As shown, this strategy can be divided into an oscillation identification module and an ADRC disturbance-free input module according to its functions. The oscillation identification includes the following specific steps, namely S411~S413.

[0104] S411. Frequency Domain Oscillation Detection:

[0105] The frequency domain detection point is set on the M3C low-frequency transformer side to detect the energy proportion of each frequency band of the low-frequency side voltage, and to obtain the energy proportion of the low-frequency side voltage at 20Hz. Among them, when When the frequency is ≤90% and lasts for one fundamental frequency cycle, a frequency domain oscillation warning signal is triggered. ;when When ≤80% and lasts for 2 fundamental frequency cycles, the frequency domain oscillation criterion signal is triggered. .

[0106] In step S411, the sliding window FFT algorithm is used to detect the energy ratio of each frequency band of the low-frequency side voltage; wherein, the sliding window FFT algorithm selects the Hanning window, the sampling frequency is 5kHz, the number of SFFT points is 256, the base frequency is 5Hz, and the voltage signal that can be measured has a frequency range of 5Hz-1280Hz. The formula for expressing it is:

[0107] ;

[0108] In the formula, X ( n )express n Voltage amplitude at twice the fundamental frequency, X (4) indicates the voltage amplitude at a frequency of 20Hz.

[0109] S412. Time-domain oscillation detection:

[0110] The time-domain detection point is set within the M3C low-frequency control structure, and the detection voltage outer loop is used. dq The per-unit value of the axis voltage is used to calculate the corresponding voltage derivative. and oscillation amplitude ;

[0111] In step S412, the numerical difference method under discrete time series is used to approximate the voltage derivative by first-order forward difference based on the voltage data at adjacent sampling times. The expression is:

[0112] ;

[0113] In the formula, and They are respectively Time and Moment q Sampled value of outer loop voltage; m This represents the reference time node for performing time-domain differential calculations; The sampling time interval for the voltage.

[0114] Time-domain oscillation early warning signal is denoted as D warn2 It satisfies the following equation:

[0115] ;

[0116] The time-domain oscillation criterion signal is denoted as D osc2 It satisfies the following equation:

[0117] ;

[0118] d The same applies to axes.

[0119] S413. When both frequency domain and time domain warning signals are triggered, an oscillation warning signal is generated; when both frequency domain and time domain criterion signals are triggered, an oscillation trigger signal is generated. The expression for S413. When both frequency domain and time domain warning signals are triggered, an oscillation warning signal is generated; when both frequency domain and time domain criterion signals are triggered, an oscillation trigger signal is generated, as follows:

[0120] ;

[0121] ;

[0122] In step S4, the non-disruptive input includes the following specific steps:

[0123] S42. When an oscillation warning signal is generated, enter the pre-synchronization state. dq Axis ADRC begins sampling and reading from the flexible low-frequency transmission system. , , and However, it was not implemented in the system for control; when an oscillation trigger signal is generated, a pre-synchronous transition hybrid control strategy is used to... dq The axis ADRC is put into operation in the system to suppress oscillations, generating dq The formula for calculating the reference value of the inner loop current is as follows:

[0124] ;

[0125] ;

[0126] In the formula, and They are respectively dq The output of the axis ADRC; and They are the original dq Output of the outer loop PI controller; The working time after the oscillation trigger signal is generated; The time constant is denoted as ADRC. After the ADRC is activated without disturbance, the continuous oscillation of the system can be regarded as a disturbance signal. With the strong robustness and disturbance rejection capability of ADRC itself, the oscillation of the system can be effectively suppressed.

[0127] The following will describe the practical application effect of the oscillation suppression method designed in this embodiment in specific implementation, and compare it with traditional control strategies and parameter configuration methods to verify the effectiveness and superiority of the present invention.

[0128] 1. Verify the ability of the ADRC-PI composite dual closed-loop control structure to suppress system oscillations. Compare the ADRC-PI control strategy with the traditional outer-loop PI-inner-loop PI control strategy through simulation. In the embodiment, the oscillation condition of the FLFT system is as follows: after 2.65 seconds of system operation, the low-frequency side of the M3C... q The inner loop PI controller parameters are faulty, proportional parameter k p The change from 4 to 2 causes a mid-to-high frequency oscillation of approximately 460Hz within the low-frequency control loop. The M3C outer loop is designed with an ADRC control structure. In this embodiment, the ADRC parameters are optimized through 500 iterations using GQPSO, resulting in approximate design parameters: d In the ADRC axis ω 0-d =1400, ω c-d =400, b 0-d =12000; q In the ADRC axis ω 0-q =2000, ω c-q =800, b 0-q =12000. The control effects of the outer-loop ADRC control strategy and the full PI control strategy under oscillating conditions, after GQPSO optimization parameter tuning, are compared as follows: Figure 6 As shown.

[0129] 2. Verify the ability of the ADRC-PI composite control structure to suppress data signal noise interference. This is demonstrated in the M3C low-frequency side simulation model of the FLFT system in the embodiment. q Random data noise with an amplitude not exceeding 0.15 pu and conforming to a Gaussian distribution is added to the axis control loop. The ADRC-PI composite control strategy and the full PI control strategy are then compared through simulation. Figure 7 and Figure 8 As shown, it can be seen that, in the presence of data noise interference, the ADRC-PI composite control strategy has a significantly better noise immunity than the inner and outer loop full PI control strategy.

[0130] 3. The ADRC-GQPSO parameter configuration method is verified to be superior to the manual parameter tuning method. The optimized oscillation suppression system is applied to the embodiment, and its control effect is as follows: Figure 9 As shown in the figure. 0.09 s after the oscillation occurred, the oscillation suppression system successfully suppressed the oscillation to a stable range, and after 0.02 s, the controlled variable completely recovered to its stable value before the oscillation occurred; in contrast, the control effect of the oscillation suppression system relying on manual ADRC parameter tuning is as follows: Figure 10As shown, after ADRC is implemented, the controlled variable still exhibits slight fluctuations, and it takes 0.22 seconds after the oscillation occurs to bring it back to its stable value before the oscillation. Its dynamic performance in oscillation suppression is significantly worse than the ADRC-GQPSO parameter configuration method. In contrast, the ADRC-PI composite control strategy, whether manually tuned or tuned using GQPSO, demonstrates superior oscillation suppression compared to the ADRC-GQPSO method. Figure 11 The traditional inner-loop PI-outer-loop PI control strategy is shown.

[0131] Therefore, compared with the traditional FLFT system, the broadband oscillation suppression method for flexible low-frequency transmission systems described in this application significantly improves the robustness and disturbance rejection capability of the FLFT system, and has good oscillation suppression capability for sudden oscillation conditions in M3C. At the same time, the optimal parameter configuration method based on GQPSO has significant advantages over manual parameter tuning, such as lower time cost and better parameter configuration effect, further proving the practical value and significance of this method.

[0132] Example 2

[0133] This embodiment provides a computer terminal, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the broadband oscillation suppression method for the flexible low-frequency power transmission system as described in Embodiment 1.

[0134] like Figure 12 As shown, the computer terminal provided in this embodiment includes: at least one processor 101, and a memory 102 connected to at least one processor 101. This embodiment does not limit the specific connection medium between the processor 101 and the memory 102. Figure 12 The example shown is the connection between processor 101 and memory 102 via bus 100. Bus 100 is... Figure 12 The connections between other components are shown in bold lines and are for illustrative purposes only, not as limiting information. Bus 100 can be divided into address bus, data bus, control bus, etc., for ease of representation. Figure 12 The bus is represented by a single thick line, but this does not indicate that there is only one bus or one type of bus. Alternatively, the processor 101 may also be called a controller; there is no restriction on the name.

[0135] In this embodiment, the memory 102 stores instructions that can be executed by at least one processor 101. The at least one processor 101 can execute the aforementioned method by executing the instructions stored in the memory 102.

[0136] The processor 101 is the control center of the device. It can connect to various parts of the control device through various interfaces and lines. By running or executing instructions stored in memory 102 and calling data stored in memory 102, the processor can perform various functions and process data, thereby monitoring the device as a whole.

[0137] In one possible design, processor 101 may include one or more processing units. Processor 101 may integrate an application processor and a modem processor, wherein the application processor mainly handles the operating system, user interface, and applications, and the modem processor mainly handles wireless communication. It is understood that the modem processor may also not be integrated into processor 101. In some embodiments, processor 101 and memory 102 may be implemented on the same chip; in some embodiments, they may also be implemented on separate chips.

[0138] Processor 101 can be a general-purpose processor, such as a central processing unit (CPU), digital signal processor, application-specific integrated circuit, field-programmable gate array or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component, capable of implementing or executing the methods, steps, and logic block diagrams disclosed in the embodiments. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the broadband oscillation suppression method for the flexible low-frequency transmission system disclosed in Embodiment 1 can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules in processor 101.

[0139] Memory 102, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules. Memory 102 may include at least one type of storage medium, such as flash memory, hard disk, multimedia card, card-type memory, random access memory (RAM), static random access memory (SRAM), programmable read-only memory (PROM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic storage, magnetic disk, optical disk, etc. Memory 102 can be any other medium capable of carrying or storing desired program code in the form of instructions or data structures that can be accessed by a computer, but is not limited thereto. In this embodiment, memory 102 can also be a circuit or any other device capable of implementing storage functions for storing program instructions and / or data.

[0140] By designing and programming the processor 101, the code corresponding to the security verification method described in the foregoing embodiments can be embedded into the chip, thereby enabling the chip to execute the code during operation. Figure 2 The steps of the broadband oscillation suppression method for the flexible low-frequency power transmission system are shown. How to design and program the processor 101 is a technique well-known to those skilled in the art and will not be described further here.

[0141] Example 3

[0142] This embodiment provides a computer-readable storage medium storing a computer program thereon. When the program is executed by a processor, it implements the steps of the broadband oscillation suppression method for the flexible low-frequency power transmission system as described in Embodiment 1.

[0143] The computer-readable storage medium may include flash memory, hard disk, multimedia card, card-type memory (e.g., SD or DX memory), random access memory (RAM), static random access memory (SRAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), programmable read-only memory (PROM), magnetic memory, magnetic disk, optical disk, etc. In some embodiments, the storage medium may be an internal storage unit of a computer device, such as the hard disk or memory of the computer device. In other embodiments, the storage medium may also be an external storage device of the computer device, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., provided on the computer device. Of course, the storage medium may include both internal storage units and external storage devices of the computer device. In this embodiment, the memory is typically used to store the operating system and various application software installed on the computer device. In addition, the memory can also be used to temporarily store various types of data that have been output or will be output.

[0144] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for suppressing broadband oscillations in a flexible low-frequency power transmission system, characterized in that, Includes the following steps: S1. Based on the characteristics of the modular multilevel matrix converter (M3C) of the flexible low-frequency transmission system, a first-order L-ADRC model is designed. This model includes a linear extended state observer, a linear state error feedback law, and disturbance compensation. S2. Construct an ADRC-PI composite dual closed-loop control strategy and configure ADRC for this strategy; wherein, the ADRC controller in this strategy is used for the outer loop voltage control of the low-frequency side of the M3C, which is completed by the first-order L-ADRC model, and the inner loop control of the low-frequency side of the M3C is completed by the PI controller. S3. The ADRC controller is configured with optimal parameters using a Gaussian quantum behavior particle swarm optimization algorithm. S4. Based on the ADRC-PI composite dual closed-loop control strategy, the oscillation of the flexible low-frequency transmission system is determined by dual parallel criteria in the frequency and time domains. According to the determination results and combined with the pre-synchronous transition hybrid control strategy, the state of the ADRC controller in the flexible low-frequency transmission system is adjusted to achieve disturbance-free connection and oscillation suppression. In step S4, the oscillation determination includes the following specific steps: S411. Frequency Domain Oscillation Detection: The frequency domain detection point was set on the M3C low-frequency transformer side. The sliding window FFT algorithm was used to detect the energy proportion of each frequency band of the low-frequency side voltage, and the energy proportion E of the low-frequency side voltage at 20Hz frequency was obtained. f＝20Hz ; where, when E f＝20Hz When E is ≤90% and lasts for one fundamental frequency cycle, a frequency domain oscillation warning signal is triggered; when E f＝20Hz When ≤80% and lasting for 2 fundamental frequency cycles, the frequency domain oscillation criterion signal is triggered; the sliding window FFT algorithm uses a Hanning window, a sampling frequency of 5kHz, 256 FFT points, a fundamental frequency of 5Hz, and can measure voltage signals with a frequency range of 5Hz-1280Hz; E f＝20Hz The formula for expressing it is: In the formula, X(n) represents the voltage amplitude at n times the fundamental frequency, and X(4) represents the voltage amplitude at a frequency of 20Hz. S412. Time-domain oscillation detection: By setting the time-domain detection point within the M3C low-frequency control structure and detecting the per-unit value of the dq-axis voltage of the outer voltage loop, the corresponding voltage derivative can be calculated. and oscillation amplitude U Mq U Md ; where, when U Mq ≥0.2pu and exists When, a time-domain oscillation warning signal is triggered, and the same applies to the d-axis; when U Mq ≥0.4 pu and exist At that time, the time-domain oscillation criterion signal is triggered, and the same applies to the d-axis; among them, the numerical difference method under discrete time series is adopted, and the voltage derivative is approximately calculated by first-order forward difference based on the voltage data of adjacent sampling times. The same applies to the d-axis; The expression is: In the formula, U (m+Δt) and U (m) These are the q-axis outer loop voltage sample values ​​at times t = m + Δt and t = m, respectively; m represents the reference time node for time-domain differentiation calculation; Δt is the voltage sampling time interval. S413. When both frequency domain and time domain warning signals are triggered, an oscillation warning signal is generated; when both frequency domain and time domain criterion signals are triggered, an oscillation trigger signal is generated.

2. The broadband oscillation suppression method for a flexible low-frequency power transmission system according to claim 1, characterized in that, Step S2 includes: The low-frequency three-phase voltage signal collected in the flexible low-frequency power transmission system is transformed from the abc three-phase stationary coordinate system to the dq synchronous rotating coordinate system through coordinate transformation, and the corresponding three-phase voltage dq axis components are obtained. Based on the control requirements of the low-frequency side of M3C, a control equation is constructed with the dq axis components of the three-phase voltage as the control target, which is used to describe the dynamic relationship between current, voltage and common-mode voltage of bridge arm in flexible low-frequency transmission system. An ADRC controller is used to replace the traditional outer loop dq axis PI controller and is referred to as dq axis ADRC. The three-phase voltage dq axis component is used as the control object of dq axis ADRC. The given reference voltage of the dq axis on the low frequency side of M3C is set as the control reference value. The inner loop current reference value of dq axis generated by the outer loop is used as the output value, thus forming the ADRC-PI composite dual closed loop control strategy. Based on the pole placement principle, the bandwidth parameters of the extended state observer in step S1 are designed, and the observed values ​​of system gain and disturbance are estimated. At the same time, the observed data are discretized to transform them into a form suitable for iterative updates by simulation software. The output value of ADRC on the dq axis is calculated through a linear state error feedback law and a disturbance compensation mechanism. The linear state error feedback law weights the error signal between the observer's observation of the controlled object and the control reference value according to the bandwidth parameter, and calculates the output value of ADRC on the dq axis by combining the observer's observation of the disturbance and the system gain estimate.

3. The broadband oscillation suppression method for a flexible low-frequency power transmission system according to claim 2, characterized in that, Step S3 includes the following specific steps: S31. Initialize the particle swarm: The initial positions of the particles are randomly generated in the solution space using a uniform probability distribution. The particle dimension is 6-dimensional, corresponding to the controller bandwidth ω of the ADRC along the dq axis. c-d and ω c-q Observer bandwidth ω 0-d and ω 0-q and the system gain estimate b 0-d and b 0-q And set the particle population size N; where the expression for the value of each particle is: In the formula, x i ω represents the value of the i-th particle, 1≤i≤N; c-d (i), ω c-q (i), ω 0-d (i), ω 0-q (i), b 0-d (i) and b 0-q (i) are all ADRC parameters to be optimized; l1 and u1 are ω c-d (i) and ω c-q (i) lower upper limit; l2 and u2 are ω 0-d (i) and ω 0-q (i) lower upper limit; l3 and u3 are b 0-d (i) and b 0-q (i) is the lower upper limit; rand(0,1) represents a random number between 0 and 1; S32. Fitness Calculation and Evaluation: Based on the requirements of the flexible low-frequency power transmission system, a multi-objective optimization function is defined, and the fitness f(x) of the corresponding parameters for each particle is calculated. i ), f(x) i The smaller the value of f(x), the better the solution; where f(x) i The expression for ) is: f(x i )=α·T s +β·e s +g·s 2 ; In the formula, α, β, and γ are all weighting factors; T s Settlement time of the flexible low-frequency transmission system after the ADRC controller is put into the M3C low-frequency side dq axis outer loop; e s The ADRC output value y and the output reference value y ref The steady-state error between them; σ 2 The total perturbation reflecting the steady-state process of ADRC is expressed as: In the formula, t0 is the time after the ADRC controller is engaged in the M3C low-frequency side dq axis outer loop; y(t) is the ADRC output value at time t; and the minimum requirement for generating a particle swarm is that there is at least one particle such that f(x i If the fitness is less than a preset minimum fitness, and the requirement is not met, return to step S31 to regenerate a new particle swarm. S33. Calculate the global optimal position: The global optimal position Mbest is the average of the historical optimal positions of all individual particles, reflecting the statistically optimal direction of the swarm search. S34. Update particle swarm positions: The particle's position update function is: In the formula, x i (t) and x i (t+1) are x i The state values ​​at times t and t+1; The pre-defined contraction and expansion coefficients; G and k are the absolute values ​​of the generated values ​​of the Gaussian probability distribution function with a mean of 0 and a variance of 1, denoted as and p is a parameter calculated and updated based on the local optimum and the global optimum, and the calculation equation is p = φ·Pbest i +(1-φ)·gbest,Pbest i Let gbest be the optimal position for the i-th particle, gbest be the position of the particle with the best fitness across the entire population, and φ be the weighting factor. S35. Fitness Optimization Update: Individual fitness optimization: If the fitness f(x) of particle i is... i )<f(Pbest i If Pbest is updated, then Pbest will be updated. i =x i ;f(Pbest i The fitness is calculated from the optimal position of particle i. Population fitness optimization: If the fitness of particle i is f(x) i If f(gbest) < f(gbest), then update gbest = x. i f(gbest) is the fitness calculated from the position of the particle with the best fitness in the entire population; S36. Repeated Iterative Loop: Repeat steps S32 to S35 until the fitness value reaches the preset precision or the maximum number of iterations is reached, then stop the loop and output the component information ω of the gbest particle. c-d (gbest), ω c-q (gbest), ω 0-d (gbest), ω 0-q (gbest), b 0-d (gbest) and b 0-q (gbest).

4. The broadband oscillation suppression method for a flexible low-frequency power transmission system according to claim 3, characterized in that, In step S31, the particle population size N = 80; l1 = 50, u1 = 800; l2 = 150, u2 = 4000; l3 = -20000, u3 = 20000.

5. The broadband oscillation suppression method for a flexible low-frequency power transmission system according to claim 3, characterized in that, In step S4, the non-disruptive input includes the following specific steps: S42. When an oscillation warning signal is generated, the system enters a pre-synchronization state, and the dq-axis ADRC begins sampling and reading the three-phase voltage dq-axis components u from the flexible low-frequency transmission system. ld u lq And the given reference voltage u on the dq axis of the M3C low-frequency side. ld-ref and u lq-ref When an oscillation trigger signal is generated, the dq-axis ADRC is put into system operation through a pre-synchronous transition hybrid control strategy to suppress oscillation. The generated dq-axis inner loop current reference value i ld-ref and i lq-ref The calculation formula is as follows: In the formula, i d-ADRC and i q-ADRC These are the outputs of ADRC on the dq axis, respectively; i d-PI and i q-PI These are the outputs of the original dq-axis outer loop PI controller; t1 is the working time after the oscillation trigger signal is generated; τ = 0.003 is the time constant.

6. A computer terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the broadband oscillation suppression method for a flexible low-frequency power transmission system as described in any one of claims 1 to 5.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps of the broadband oscillation suppression method for flexible low-frequency transmission systems as described in any one of claims 1 to 5.

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