46 results about "Repetitive control" patented technology

The invention relates to the technical field of power systems, in particular to a UPQC harmonic compensation method and system based on repetitive control, and the method comprises the steps: obtaining a load current signal and a voltage signal of a power distribution network, and extracting a harmonic instruction current based on the load current signal; and inputting the harmonic instruction current into a feed-forward channel constructed based on an adaptive filter, and generating a feed-forward control quantity. The phase and frequency of the voltage signal of the power distribution network are tracked in real time through a digital phase-locked loop, the fundamental frequency of the power grid is accurately solved, and the power distribution network can be accurately controlled. The internal model period and the phase lead compensation amount of the frequency adaptive repetitive controller are dynamically calculated, and the internal model structure of the repetitive controller is always matched with the current power grid frequency by updating the two core parameters in real time, so that the compensation precision decline caused by frequency deviation is avoided; and high-precision suppression of the periodic harmonic waves can be realized in a normal fluctuation range of the fundamental wave frequency of the power grid.

The invention belongs to the technical field of power electronics of power supply or power distribution, and provides a control method of a three-phase four-wire inverter, a controller and an inversion control system. A first control component is generated by using a phase angle, an inversion side three-phase current sampling value and a proportional integral compensator; a second control component and a third control component are generated by using a power grid voltage angular frequency, a neutral line current sampling value, a repetitive controller and a proportional resonance controller, the three control components are combined to control an inverter power switch tube, a proportional integral compensator is still adopted, the algorithm is simple, parameters are easy to design, and the reliability is high. And meanwhile, a repetitive-proportional resonance (RC-PR) composite controller is utilized to realize suppression of neutral line fundamental wave and harmonic current, and the method has faster dynamic response to load abrupt change, so that optimization of dynamic performance and steady-state performance is realized.

The invention discloses a repetitive control-based circulating current suppression method between grid-forming type energy storage units, and relates to the technical field of power electronics and control, the method adopts three rings of power, voltage and current to regulate and control a grid-forming type multi-machine parallel inverter, a repetitive controller is introduced into a current inner ring, and the repetitive controller is introduced into a current outer ring to control the circulating current between the grid-forming type energy storage units. The method has the advantages that periodic harmonic current is accurately tracked and suppressed, meanwhile, a narrow-band resonance circuit and LC filter state feedback and pole assignment design are introduced into a current loop, LC filter resonance peaks are effectively eliminated through LC filter state feedback and pole assignment, typical harmonic circulation in a parallel system is further suppressed through the narrow-band resonance circuit, and the harmonic current suppression efficiency is improved. Efficient suppression of circulation among the units and uniform distribution of power are further realized; according to the technical scheme, the stable operation of the system can be guaranteed, the power sharing capability and the grid-connected adaptability of the energy storage unit are improved, a complex distributed communication structure is avoided, and the operation reliability of the network construction type energy storage system in a complex power grid environment is improved.

The invention provides an off-line and on-line collaborative optimization MMC harmonic elimination method for harmonic constraint driving, and relates to the technical field of power electronics, S1, generating a switching angle training set and a parameter fluctuation label through clustering analysis and a differential evolution algorithm according to power grid parameters and MMC operation parameters; and S2, extracting harmonic characteristics by using a harmonic detection technology, predicting a switching angle through a neural network, and outputting a final switching angle in combination with a repetitive control link to realize harmonic suppression. According to the off-line and on-line collaborative optimization MMC harmonic elimination method based on harmonic constraint driving, an MMC under a low level number can always keep a low harmonic content level under the complex conditions of different modulation ratios and access to a new energy field station.

The invention relates to a dual three-phase permanent magnet synchronous motor model-free prediction repetitive control method and system based on a double-subspace virtual vector, and the method comprises the steps: decomposing the vector of a motor into a fundamental wave subspace and a harmonic wave subspace which are orthogonal to each other based on an obtained operation parameter, and constructing an independent super-local model in the two subspaces; constructing a linear expansion state observer in the fundamental wave subspace, and constructing a repetitive expansion state observer based on repetitive control in the harmonic wave subspace; respectively synthesizing an independent virtual voltage vector set and a decoupling virtual voltage vector set in the two subspaces; and calculating reference voltage vectors of the two subspaces, selecting an optimal virtual voltage vector and an optimal decoupling virtual voltage vector, respectively calculating optimal duty ratios, synthesizing control signals applied to each bridge arm of the inverter, and driving the dual three-phase permanent magnet synchronous motor. According to the method, model-free control of double sub-spaces is realized, model parameters of a motor system of an algorithm are controlled, and better robustness is shown when the parameters are mismatched.

This application provides a control method, system, and electronic device for a PWM rectifier. The control method includes: determining the actual current of the PWM rectifier and determining a current error based on the actual current and a reference current; obtaining a first control parameter based on the current error using a preset algorithm; determining an error compensation value based on the current error using a repetitive controller, and compensating the first control parameter with the error compensation value to obtain a second control parameter; determining the fundamental frequency of the modulation wave based on the second control parameter, and obtaining a control signal based on the fundamental frequency of the modulation wave using a discontinuous pulse width modulation (DPWM) method to control the PWM rectifier. This application introduces a repetitive controller into the discontinuous pulse width modulation (DPWM) method, which improves the problem of large current harmonics caused by periodic errors due to periodic entry into clamping state in the DPWM modulation method, thereby improving control accuracy.

The invention relates to the technical field of power systems, in particular to an event-triggered proportional-integral repetitive controller and method and a related device. Two channels of the event triggering block are respectively provided with two adjusting coefficients, and tracking error signals are respectively input into a repetitive controller and a proportional-integral controller after being adjusted; when a triggering condition is met, two adjustment coefficients of a forward channel of the event triggering block change along with time; the tracking error is increased, the adjustment coefficient of the repetitive control channel is reduced, and the adjustment coefficient of the proportional-integral channel is increased; and after a trigger period, the two adjustment coefficients of the event trigger block are gradually recovered to default values along with the reduction of the tracking error signal. According to the invention, decoupling of the proportional-integral repetitive controller is realized, the dynamic performance is improved, and output distortion of multiple periods caused by mismatching of the dynamic performance of the proportional-integral controller and the repetitive controller is avoided.

The invention provides a photovoltaic inverter harmonic suppression system and method, and the method comprises the steps: obtaining a target current error of a current period, enabling a repetitive control branch to generate a branch period delay of the current period according to the target current error, a gain coefficient corresponding to the target current error and a branch period delay of a previous period, and collecting the branch period delay as a total delay of the current period; and inputting the total delay of the current period into a PI controller, so that the PI controller generates a target voltage instruction. The tracking capability of the PI controller on the fundamental current is reserved, the current inner loop design of a common inverter is not affected, and the suppression effect on the periodic harmonic waves is enhanced through the repetitive controller. Meanwhile, by optimizing the design of the repetitive controller, the repetitive controller becomes a composite repetitive controller comprising at least two repetitive control branches, the effective bandwidth of the repetitive controller is widened, the repetitive controller can adapt to the fluctuation of the power grid frequency, and therefore the excellent grid-connected current harmonic suppression performance is kept within the wide frequency change range.

The application discloses a network-constructing energy storage converter control method based on a repetitive control inner loop, comprising the following steps: generating a power grid angular frequency reference value by integrating adjustment of an active power deviation; generating a power grid amplitude reference value by integrating adjustment of a reactive power deviation; generating an inner loop current reference instruction through a voltage loop controller according to a voltage loop voltage reference value, superposition of a power grid current feedforward branch and a voltage loop dq decoupling branch; generating a current loop voltage reference value through a current loop controller and a repetitive controller in parallel processing according to the inner loop current reference instruction, and superposition of a current loop dq decoupling branch; and generating a corresponding output current according to the current loop voltage reference value. By designing a lead compensation link and a compensator, the problem of difficult parameter setting and easy instability of a traditional repetitive controller is improved, and stable operation of the system is ensured.

The application discloses a control strategy based on combination of a pre-filter friction compensator and improved repetitive control, and specifically comprises the following steps: step 1, a pre-filter friction compensator is added to a P / PI cascade controller to improve the anti-friction interference capability of a driving system; step 2, a transfer function of an output voltage of the driving system and a tracking error is determined; step 3, specific parameters of a LuGre model in the pre-filter friction compensator are obtained; step 4, a repetitive controller is designed; step 5, an action time period of the repetitive controller determined in step 4 is set at motion commutation to obtain a segmented repetitive control; and step 6, the segmented repetitive control obtained in step 5 is combined with the designed pre-filter friction compensator to form an improved repetitive control framework. The method combines the pre-filter friction compensation control with the segmented repetitive control, greatly improves the error and convergence rate at the motion commutation of each cycle, and reduces the influence of the friction interference on the product processing quality.

This invention relates to a model-free predictive repetitive control method and system for a dual-subspace virtual vector dual-three-phase permanent magnet synchronous motor. Based on the acquired operating parameters, the motor's vectors are decomposed into mutually orthogonal fundamental and harmonic subspaces, and independent hyperlocal models are constructed in both subspaces. A linear extended state observer is constructed in the fundamental subspace, and a repetitive extended state observer based on repetitive control is constructed in the harmonic subspace. Independent virtual voltage vector sets and decoupled virtual voltage vector sets are synthesized in the two subspaces, respectively. Reference voltage vectors for the two subspaces are calculated, and the optimal virtual voltage vector and optimal decoupled virtual voltage vector are selected. The optimal duty cycle is calculated for each subspace, and control signals are synthesized and applied to each arm of the inverter to drive the dual-three-phase permanent magnet synchronous motor. This invention achieves model-free control in a dual-subspace manner, and the control algorithm for the motor system's model parameters exhibits better robustness in the event of parameter mismatch.

The present disclosure relates to a kind of energy storage converter multi-mode control method and device.Wherein, the method includes: for energy storage converter in grid-connected mode, by creating second-order infinite impulse response IIR filter, establish low voltage ride through control strategy based on compliance repeat control;For energy storage converter in off-grid mode, three-phase four-bridge topology is used to provide zero sequence path, establish preset proportional resonant control strategy;For energy storage converter in grid-constructing mode, establish parallel pre-synchronization control strategy;Low voltage ride through control strategy based on compliance repeat control, preset proportional resonant control strategy, parallel pre-synchronization control strategy are used to realize multi-mode control to the energy storage converter.The present disclosure can set any resonant frequency and filter radius to suppress the resonant peak, ensure system stability, compared with traditional pre-synchronization method only using its frequency modulation characteristics, without additional control link can complete pre-synchronization, greatly save control resources.

The application discloses a torque ripple suppression method for a brushless doubly-fed motor, which comprises the following steps: firstly, a current loop and a rotating speed loop model of the brushless doubly-fed motor are established; then, an active disturbance rejection controller is established according to the current loop and the rotating speed loop model, wherein the active disturbance rejection controller comprises a d-axis improved current controller, a q-axis current loop active disturbance rejection controller and a rotating speed loop active disturbance rejection controller; the d-axis improved current controller comprises a d-axis current loop active disturbance rejection controller and an improved repetitive controller connected in parallel with the d-axis current loop active disturbance rejection controller; and then, the brushless doubly-fed motor is controlled by using the established active disturbance rejection controller. The active disturbance rejection controller is combined with the improved repetitive controller, the extended state observer is used for disturbance estimation, and the disturbance contains a coupling term, so that the current dynamic response is faster, and the parameter robustness is stronger; meanwhile, the improved repetitive controller connected in parallel can overcome the high-frequency current harmonics introduced by uncontrolled rectification, and can also limit the dynamic response to not produce excessive overshoot when the working condition is suddenly changed.

This invention belongs to the field of shield tunneling construction control technology, and specifically discloses a method and system for adaptive control of shield machine attitude under shield tunneling conditions. The method includes: constructing a virtual construction environment for TBM attitude adaptive control; determining the state and reward of a reinforcement learning model during TBM tunneling, wherein the TBM state is updated according to constitutive relations, and the reward is used for forward speed and TBM attitude; constructing a DGDPG model for the shield tunneling process based on the above virtual construction environment, state, and reward, and optimizing and training the DGDPG model; and evaluating the TBM tunneling process based on the optimized DGDPG model. This invention addresses the characteristics of traditional shield tunneling processes, such as non-repeatability, poor control accuracy, and low level of intelligence, by achieving high-precision adaptive control of shield machine tunneling attitude based on deep reinforcement learning methods, thereby overcoming the shortcomings of current shield machine attitude prediction and optimization methods in engineering applications.

The application discloses a permanent magnet synchronous motor NVH optimization method based on frequency adaptive repetitive control, and comprises the following steps: S1, an air gap magnetic field model generated by a permanent magnet and an armature reaction is established; S2, a relationship between a radial electromagnetic force order and a three-phase current harmonic order is derived according to the air gap magnetic field model; S3, a frequency adaptive repetitive control algorithm is used to suppress the harmonic of the dq-axis current; and S4, a joint simulation platform is built to verify the effect. The frequency adaptive repetitive controller and the PI controller are used to suppress the harmonic in the current loop, the harmonic content of the three-phase current of the motor is greatly reduced, and the NVH performance of the motor is improved.

The application relates to the technical field of brushless direct-current motors, in particular to an optimization control method for a permanent magnet brushless direct-current motor servo system, which comprises the following steps: S1.1: obtaining an equivalent system basic model of the permanent magnet brushless direct-current motor servo system; S1.2: improving the equivalent system basic model of the permanent magnet brushless direct-current motor servo system, and establishing a compound repetitive control law; and S1.3: optimizing control of the parameters of the equivalent system basic model of the permanent magnet brushless direct-current motor servo system. The application proposes a repetitive control system parameter optimization method based on an improved disturbance estimator compensation, establishes an optimization control model of system parameters based on the stability of the system, realizes synchronous optimization design of the parameters of a system repetitive controller, an improved disturbance estimator and a feedback controller, and makes the system simultaneously have satisfactory non-periodic disturbance suppression performance and periodic signal tracking performance.

The invention discloses a high-reliability complex coefficient repetitive control grid-connected inverter control system and method suitable for a power supply protection scene, and the method comprises the steps: building an LCL type grid-connected inverter mathematical model under an alpha-beta static coordinate system for a three-phase grid-connected inverter, and saving Park transformation and decoupling calculation under a dq coordinate system; a complex coefficient filter H (s) and a complex coefficient repetitive controller are designed to form a double-input double-output control structure, and a complex coefficient imaginary part omega m is set to be equal to a fundamental frequency omega 0, so that the gain of the controller at the fundamental frequency is infinite, and complete tracking of periodic signals is realized; and the dynamic response capability of the system is improved by combining an output feedback control law. According to the method, the grid-side voltage imbalance and harmonic pollution can be effectively suppressed, the grid-connected current THD can be remarkably reduced, and the method has good dynamic control performance and robustness, is suitable for a grid-connected power generation system of new energy such as solar energy and wind energy, and plays an important supporting role in improving the power supply reliability and supply guarantee capability of a power system under the new energy access background.

The present invention aims at obtaining an optimal solution of an optimization problem at high speed and efficiently with a simple optimization algorithm. The solution search system is provided with: a plurality of data generating units (11-1 / ... / 11-i); a variation setting unit (16) that supplies a variation probability to the data generating units and sets the occurrence frequency of data generated by the data generating units to be non-uniform so that the occurrence frequency of a specific variable and the occurrence frequency of other variables form different values; a plurality of data converting units (12-1 / ... / 12-i) that read the data generated by the data generating units and convert them into information; an output adjustment unit (14) that transmits an output adjustment signal, or an output adjustment signal and a value of the variation probability, to the data generating units; and a feedback control unit (13) that repeatedly controls the action of transmitting the output adjustment signal, or the output adjustment signal and the value of the variation probability, to the data generating units when an optimal solution is not obtained.

The application discloses a kind of based on repeated self-adapting cascade type power grid simulator inverter side control method, comprising: acquisition output voltage and output current;The output voltage is subtracted from given signal to obtain error voltage;Error voltage is inputted repeated controller to obtain first control signal, and first control signal is added to given signal to obtain the reference voltage of self-adapting control;Self-adapting control reference voltage, output voltage, output circuit input self-adapting controller and carry out self-adapting processing, obtain second control signal;Output current is inputted feedforward compensator and is compensated, and compensated control signal is obtained;Compensated control signal and second control signal are added to obtain third control signal;Third control signal is modulated to obtain SPWM pulse of the SPWM pulse of control cascade type power grid simulator inverter side output voltage.The application is based on voltage outer loop repeated control to realize no static error tracking, and harmonic tracking capability is improved.

The invention discloses a control method, system and device for automatic switching of forward and reverse water supply and a storage medium. The method comprises the steps that the full-open duration of a four-way reversing valve is obtained, first judgment is conducted on the full-open duration, and a unit technical water supply system meeting the switching condition is started according to the first judgment result; acquiring operation parameters of the unit technical water supply system, performing second judgment on the operation parameters, and controlling a four-way reversing valve to execute flow direction switching operation according to a second judgment result; third judgment is conducted on the operation parameters of the unit technical water supply system executing the flow direction switching operation, according to the third judgment result, the unit technical water supply system is stopped, the continuous operation duration of the four-way reversing valve is reset, automatic switching of forward and reverse water supply is repeatedly controlled, the pressure and workload of workers are relieved, and the working efficiency is improved. And safe and stable operation of the unit is ensured.

The invention discloses a symmetric six-phase permanent magnet synchronous motor turn-to-turn short circuit fault-tolerant control method based on IRC-DOB, and belongs to the field of permanent magnet synchronous motor fault-tolerant control. The control method comprises the following steps: S1, based on a voltage equation and a short circuit equation of the symmetric six-phase permanent magnet synchronous motor under a turn-to-turn short circuit fault, establishing a symmetric six-phase permanent magnet synchronous motor turn-to-turn short circuit fault circuit model of a----coordinate system through vector space decoupling transformation; s2, deriving a torque expression after the turn-to-turn short circuit fault of the symmetric six-phase permanent magnet synchronous motor based on the influence of the current and the short circuit current of the----coordinate system on the torque; s3, based on the influence of the current control quantity after the turn-to-turn short circuit fault on the torque after the fault, deriving a current compensation value expression required for suppressing the torque ripple after the fault; and S4, suppressing the torque ripple after the turn-to-turn short circuit fault by adopting a fault-tolerant control method based on the improved repetitive control observer. After a turn-to-turn short circuit fault occurs, turn-to-turn short circuit torque ripple suppression of the symmetric six-phase permanent magnet synchronous motor can be realized.

An induction device includes a plurality of induction areas which can be controlled independently from one another, and a control unit configured to control the plurality of induction areas within a control period from a first control interval and a second control interval repetitively with an alternating current frequency and to supply the plurality of induction areas with energy. The control unit operates in the first control interval at least two of the plurality of induction areas with a first phase shift to minimize interference.

The application discloses a dead zone compensation method and device of a current loop, a motor control system and a storage medium, and the method comprises the following steps: based on a rotor electrical angle of a current axis, an array of the current axis is constructed, the current axis is a d-axis or a q-axis; the array of the current axis contains N elements, the rotor electrical angle of the current axis is divided into N equal parts, and each element is used for storing accumulated current error of a corresponding rotor electrical angle history period of the current axis, and N is a positive integer; based on the array of the current axis, a position domain repetitive control based on the rotor electrical angle of the current axis is adopted to perform dead zone compensation on a current loop of the current axis. According to the scheme, the position domain repetitive control based on the rotor electrical angle is added to the d-q axis current loop, so that the dead zone compensation can be realized, and the compensation effect is relatively ideal.

This processing system is provided with: an acquisition unit, a first calculation unit (processing surface shape calculation unit), a second calculation unit (setting value calculation unit), and an output unit. The acquisition unit acquires processing data obtained during workpiece processing performed by a tool included in a processing machine. The first calculation unit calculates shape data related to a processing shape of the workpiece, on the basis of the processing data acquired by the acquisition unit. The second calculation unit calculates a setting value of repeated control on the processing machine, on the basis of the shape data calculated by the first calculation unit. The output unit outputs the setting value calculated by the second calculation unit to a repetition control unit for exercising the repeated control.

The application provides a three-level inverter multi-rate control method, for any control axis of alpha beta 0: a voltage target value is subtracted from an actual value to obtain a voltage deviation, and a subscript is a control axis code; a repetitive controller is used as an input quantity, and an output result obtained is added to obtain; a state feedback controller is based on phase currents of alpha beta 0 and a control signal at a previous moment to output a control signal, and finally, the inverter is controlled to operate via 3D-SVPWM. The three-level inverter multi-rate control method can improve the dynamic performance and phase characteristics of the system by introducing the state feedback controller under the multi-rate control framework, configuring the closed-loop poles of the inverter discrete model, and thereby improving the stability of the system under the condition of downsampling.

The invention discloses a PCS zero sequence control method based on an unbalanced load, and belongs to the field of energy storage converter control. The method comprises the steps that PCS three-phase output currents are obtained and added to obtain a zero-sequence component, and low-pass filtering is carried out on the zero-sequence component; detecting PCS positive and negative bus voltages, calculating a bias voltage value, and performing PI adjustment on the bias voltage value and a preset reference value; inputting a PI regulation result, and performing PI control and repetitive control combined modulation on the filtered zero-sequence component to obtain a modulation signal; and inversely transforming the modulation signal into an ABC three-phase coordinate system to obtain a three-phase modulation signal, and controlling a PCS output waveform after per unit. Extra hardware is not needed, and the cost and the implementation difficulty are reduced; excessive dependence of system parameters is avoided, and robustness is high; under the extreme unbalanced load, the zero-sequence current can be restrained to about 3A, the bus voltage deviation is small, normal active / reactive regulation of the PCS is ensured, and the quality of the output voltage reaches the standard.

The invention provides a seismic isolation structure AMD intelligent linkage control system based on a seismic energy storage principle, which comprises a seismic isolation support, a hydraulic inerter damper, an energy transfer module, an energy storage module and a sensor network, and is provided with a variable damping intelligent control unit, an active tuned mass damper and an AMD intelligent control unit. Structural dynamic response, the stress state and the energy state of the shock insulation support are obtained in a unified mode through the linkage control unit, and the damping characteristic of the hydraulic inerter damper and the control force of the active tuned mass damper are coordinated at the same time on the basis of a collaborative optimization strategy. The control direction, the control time sequence and the energy use of the two types of control units are kept consistent. According to the method, the acceleration of the upper structure can be reduced, interlayer displacement can be controlled, the shock insulation support is prevented from being pulled, the energy utilization efficiency is improved, conflicts and repeated control in an independent control mode are avoided, and therefore the overall anti-seismic performance of the shock insulation structure under the complex seismic mode and strong seismic working conditions is improved.

This invention relates to a two-degree-of-freedom active disturbance rejection (ADNR) control method for a dual three-phase motor driven by a nine-switch current source, belonging to the field of permanent magnet motor control technology. The invention addresses the coupling problem between tracking and disturbance rejection performance in traditional ADNR control for dual three-phase permanent magnet synchronous motors based on current source inverters. The invention includes: establishing a mathematical model of the dq-axis current loop of a nine-switch current source inverter in a synchronous rotating coordinate system, incorporating both periodic and aperiodic disturbances; designing an improved extended state observer, removing the error correction term for the current tracking signal and its differential signal update law in the traditional extended state observer, and designing the disturbance update law as a proportional-integral-repetitive control structure; constructing a two-degree-of-freedom ADNR controller based on the control characteristics of the current source inverter, and independently adjusting the reference tracking performance and disturbance rejection performance based on the output of the improved extended state observer, achieving complete decoupling between the two.

The invention discloses an inverter repetitive control method, system and equipment based on phase compensation. The method is applied to an inverter control system, the inverter control system comprises a repetitive controller and a lead correction link used for phase compensation, the lead correction link is arranged at the output end of the repetitive controller, and the method comprises the following steps: obtaining an error signal between an inverter output signal and a given reference signal; inputting the error signal into a repetitive controller to generate a preliminary control signal; performing phase lead compensation on the preliminary control signal through a lead correction link to generate a target control signal; and acting the target control signal on a controlled object of an inverter control system to realize phase compensation-based inverter repetitive control. According to the method, the problems of insufficient phase margin and poor stability caused by inherent phase lag of a repetitive control algorithm can be solved.

The present application relates to the technical field of power system, and particularly relates to a UPQC harmonic compensation method and system based on repetitive control, comprising: obtaining a load current signal and a voltage signal of a power distribution network, and extracting a harmonic instruction current based on the load current signal; inputting the harmonic instruction current to a feedforward channel constructed based on an adaptive filter to generate a feedforward control amount, the present application tracks the phase and frequency of the voltage signal of the power distribution network in real time through a digital phase-locked loop, accurately calculates the fundamental frequency of the power grid, and dynamically calculates the internal mode period and phase lead compensation amount of the frequency adaptive repetitive controller according to the same, by updating the two core parameters in real time, the internal mode structure of the repetitive controller is always matched with the current power grid frequency, the compensation accuracy degradation caused by frequency deviation is avoided, and high-precision suppression of periodic harmonics can be achieved within the normal fluctuation range of the fundamental frequency of the power grid.