Suppression Of Oscillations Research Articles

Oscillation Suppression of Grid-Following Converters by Grid-Forming Converters with Adaptive Droop Control

The high penetration of renewable energy sources (RESs) and power electronics devices has led to a continuous decline in power system stability. Due to the instability of grid-following converters (GFLCs) in weak grids, the grid-forming converters (GFMCs) have gained widespread attention featuring their flexible frequency and voltage regulation capabilities, as well as the satisfactory grid-supporting services, such as inertia and damping, et al. Notably, the risk of wideband oscillations in modern power grids is increasingly exacerbated by the reduced number of synchronous generators (SGs). Thus, the wideband oscillation suppression method based on adaptive active power droop control of GFMCs is presented in this paper. First, the stability of the hybrid grid-forming and grid-following system is obtained according to the improved short circuit ratio (ISCR), where the GFMC is in parallel at the point of common coupling (PCC) of the GFLC. Then, an adaptive adjustment strategy of the active power droop control is proposed to enhance the oscillation suppression capability across the full frequency range, thereby mitigating the wideband oscillation caused by phase-locked loop (PLL) synchronization in the GFLCs. Additionally, a first-order inertia control unit is added to the active and reactive power droop controllers to mitigate frequency and voltage variations as well as suppress potential mid-to-high frequency resonance. Finally, the wideband oscillation suppression strategy is validated by the simulation and experimental results.

Analysis and Suppression of Oscillations in Doubly Fed Variable Speed Pumped Storage Hydropower Plants Considering the Water Conveyance System

The doubly fed variable speed pumped storage (DFVSPS) system is a hydraulically, mechanically, and electrically coupled system, and the characteristics of the components from the water conveyance system to the transmission line need to be fully considered in the oscillation analysis. Hence, the model of the water conveyance system is included to investigate the oscillation characteristics of the DFVSPS connecting to the grid via a series-compensated line. A small-signal state-space model of the DFVSPS system in the generation mode is first established. The oscillation characteristics of the DFVSPS are studied, and the dominant state variables for each oscillation mode are identified. The impact of system parameters on oscillations is further studied, and simulations are carried out to validate the accuracy of the model. The results indicate the oscillation mode of the DFVSPS comprises the electrical sub-synchronous oscillation (SSO) mode and the hydraulically, mechanically coupled low-frequency mechanical oscillation modes. When the series compensation level is high, the SSO becomes divergent, and the system is more likely to be unstable. Optimizing the rotor-side control parameters and the governor control parameters, sub-synchronous and low-frequency oscillations could be effectively suppressed, respectively. This study provides reference suggestions for the development and use of the future DFVSPS system.

Experimental study on how the settings of plasma affect its effectiveness of suppression of thermoacoustic oscillations in a Rijke tube

Thermoacoustic instabilities, frequent in a wide range of combustors, arise from the intricate coupling between the flame’s unsteady heat release and the combustor acoustic. The application of plasma, characterized by its substantial local energy addition and radical generation, has demonstrated potential in disrupting this coupling and thereby mitigating thermoacoustic oscillations. Notably, open-loop control using discharge plasma has been successfully implemented to suppress self-excited oscillations in a Rijke tube setup. Considering the broader context of a complex system that integrates both thermoacoustic systems and discharge plasma, experiments were done to see its performance in stability under different arrangement and discharge repetition rates of discharge plasma. These experimental investigations identified critical operating conditions essential for complete suppression: (A) the optimal location of discharge actuations, and (B) the minimum energy required for complete suppression. Moreover, the impact of discharge plasma, particularly when tuned to the eigenfrequencies of oscillations within the thermoacoustic system, was thoroughly examined. The insights gained from these successful suppression trials are instrumental in guiding the strategic design of both physical arrangement and electrical configurations for the control of combustion instabilities via discharge plasma. Furthermore, through the photographing of the swinging arcs and their thermal disturbances by high-speed camera and high-speed schlieren, the characteristics of arcs’ thermal disturbances and the reasons affecting its suppression effectiveness were determined.

Development of means for suppressing the negative effects of interaction between the pilot and reentry and other high-speed vehicles

Several novel active and passive means for the suppression of pilot-induced oscillations are considered in the paper. The potential of the proposed means in eliminating Category I, II, and III pilot-induced oscillations was studied in ground-based simulation for two controlled element dynamics corresponding to an aerospace vehicle and a second-generation supersonic transport. The experiments demonstrated that the highest effectiveness in suppressing pilot-induced oscillations and improving task performance is provided by integrating both proposed active suppressors with one of the passive prefilters.

A General [P Q]-[ω V] Model of Hybrid GFM/GFL Multi-VSC Systems: Power Oscillation Analysis and Suppression Method

A General [P Q]-[ω V] Model of Hybrid GFM/GFL Multi-VSC Systems: Power Oscillation Analysis and Suppression Method

A Smith Predictor Based High-Frequency Oscillation Suppression Method for VSC-HVDC System

A Smith Predictor Based High-Frequency Oscillation Suppression Method for VSC-HVDC System

Pressure oscillation and suppression method of large-aspect-ratio solid rocket motors

A two-dimensional large eddy simulation numerical model is proposed to study the transient vortex flow and pressure oscillation of a large-aspect-ratio solid rocket motor. The numerical model is validated through experimental data, finite element analysis and cumulative error analysis. The numerical simulations are executed to obtain the characteristics of the vortex-acoustic and pressure oscillation. The results show that the burning surface regression decreases the motor aspect ratio, increasing the corresponding natural frequency from 260 Hz to 293 Hz. The pressure oscillation phenomenon is formed due to the vortex-acoustic coupling. Decreasing the corner vortex shedding intensity shows negative effects on the dimensionless amplitude of the pressure oscillation. The head cavity without the injection can decrease the vortex-acoustic coupling level at the acoustic pressure antinode. The modified motor with head cavity can obtain a lower dimensionless oscillating pressure amplitude 0.00149 in comparison with 0.00895 of the original motor. The aspect ratio and volume of the head cavity without the injection have great effects on the pressure oscillation suppression, particularly at the low aspect ratio or large volume. The reason is that the mass in the region around the acoustic pressure antinode is extracted centrally, reducing the energy contribution to the acoustic system. With the volume increasing, the acoustic energy capacity increases.

Research on Broadband Oscillation Suppression Strategy in Power System Based on Genetic Algorithm

This examination presents an original Broadband Oscillation Concealment Procedure in Power Systems utilizing a Genetic Algorithm (GA). The philosophy’s suitability is deliberately assessed through comprehensive examinations, including affiliation investigation, strength appraisal, and near investigations with elective optimization algorithms. Results show that the GA-based approach displays predominant affiliation, appearing at a health worth of 0.05 after 100 ages, beating Particle Swarm Optimization (PSO), Ant Colony Optimization (ACO), and Simulated Annealing (SA). Strength examination features the versatility of the proposed procedure, with a standard wellbeing worth of 0.08 ± 0.02 under changing power framework conditions. Similar investigation against related work reveals the procedure’s advantage, showing its genuine breaking point with regards to helpful broadband oscillation concealment. The GA-based philosophy changes speedy mixing and computational capacity, with an ordinary execution season of 120 seconds. The examination contributes important pieces of information into power framework strength, offering a good answer for mitigating broadband oscillations in various working situations.

Suppression and Analysis of Low-Frequency Oscillation in Hydropower Unit Regulation Systems with Complex Water Diversion Systems

Suppression and Analysis of Low-Frequency Oscillation in Hydropower Unit Regulation Systems with Complex Water Diversion Systems

Transition among oscillation death, amplitude death, and revival of oscillation in coupled time-delayed systems with diffusivity and common environment

In this paper, we study the transition between different oscillation suppression, revival of oscillation, and oscillatory states in time-delayed chaotic oscillators coupled through simultaneous diffusive and environmental coupling. The present paper, for the first time, reports the occurrence of oscillation death and nontrivial amplitude death states in coupled intrinsic time-delayed systems. Moreover, we explore the revival of the oscillations from these diverse oscillation suppression states. We analyze the stability of the coupled time-delayed system and through extensive numerical investigations, we delineate all the dynamical states in the parameter space. The study is extended to a network of time-delayed oscillators and identical transition scenarios have been obtained. Finally, we support our results in an electronic hardware circuit-based experiment and demonstrate that all the transition scenarios are robust enough in a real world system where the presence of noise, fluctuations, and parameter mismatch are inevitable.

Takagi–Sugeno Fuzzy Parallel Distributed Compensation Control for Low-Frequency Oscillation Suppression in Wind Energy-Penetrated Power Systems

In this paper, a Takagi–Sugeno fuzzy parallel distributed compensation control (TS-PDCC) is proposed for low-frequency oscillation (LFO) suppression in wind energy-penetrated power systems. Firstly, the fuzzy C-mean algorithm (FCMA) is applied to cluster the daily average wind speed of the wind farm, and the obtained wind speed clustering center is used as the premise variable of TS-PDCC, which increases the freedom of parameter setting of the TS fuzzy model and is closer to the actual working environment. Secondly, based on the TS fuzzy model, the TS-PDCC is designed to adjust the active power output of the wind turbine for LFO suppression. To facilitate the computation of controller parameters, the stability conditions are transformed into a set of Linear Matrix Inequalities (LMIs) via the Schur complement. Subsequently, a Lyapunov function is designed to verify the stability of the wind energy-penetrated power system and obtain the parameter ranges. Simulation cases are conducted to verify the validity and superior performance of the proposed TS-PDCC under different operating conditions.

A Transient Damping Improvement Strategy for Enhancing Grid-Connected Active Power Response Performance of VSG

The given power and grid frequency disturbances can cause transient oscillations and steady-state deviations in the output power of a virtual synchronous generator (VSG), which can be effectively addressed by adding transient damping. However, this approach may result in significant power overshoot. This article proposes an improved VSG control strategy based on transient electromagnetic power feedback compensation and a small-signal model reduction scheme. Firstly, the grid-connected active closed-loop small-signal models of typical VSG control and transient damping VSG control are established, respectively. The transient oscillation suppression mechanism of active power is revealed through root locus and frequency response analyses, and the power overshoot characteristics of the two control strategies are analysed by combining them with the system of zero points. Secondly, the active transient feedback compensation method and the small-signal model reduction design method are introduced in detail. Finally, comparative analysis experiments are conducted using the Matlab/Simulink and hardware-in-the-loop experimental platform. It is verified that the proposed control strategy can suppress transient oscillations in active power, prevent steady-state deviations, and effectively mitigate the power overshoot problem of the system.

A Wide Range Zero‐Voltage Switching Phase‐Shifted Full‐Bridge Converter With No Duty Cycle Loss and Low Rectifier Oscillation

ABSTRACTThe phase‐shifted full‐bridge (PSFB) converter has been widely used in DC/DC converters due to its soft‐switching characteristics. However, it still has many drawbacks. In order to solve the shortcomings of the PSFB converter, such as limited soft‐switching range, high loss of duty cycle, and high oscillating voltage of the secondary rectifier, a PSFB converter based on parallel variable inductor and series blocking capacitor is proposed in this study. A wide range of soft switching, low rectifier oscillation voltage, and no duty cycle loss can be realized by the auxiliary current‐controlled variable inductor and reasonable blocking capacitor design. In this study, the mechanism of soft switching and suppression of oscillation is discussed and some of the designs are given. Finally, the experimental results of a 200 W/50 kHz prototype are constructed in the laboratory to verify the feasibility and effectiveness of the proposed converter.

Few-Human-Interaction Reinforcement Learning for Autonomous Transbronchial Intervention.

The transbronchial interventional surgery presents challenges with winding and convoluted pathways, prone to compression and friction. Current autonomous planning struggles to reach deeper bronchial positions, and hard to consider multiple conflicting goals simultaneously. This article introduces an innovative planning scheme with preference weights to achieve smooth, frictionless, and collision-free autonomous transbronchial intervention with continuum robot (CR). A few-human-interaction twin-delayed deep deterministic policy gradient (FHITD3) generated from surgeon preference guidance is proposed, which determines the optimal strategy for the motion of CR. Preference knowledge is generated through interaction between human and few diversity samples. An abstract actuator space description is proposed for the posture and position representation of CR during movement within bronchus. A contact motion analysis strategy is proposed to calculate real-time attitude of CR in contact with bronchus. In addition, an oscillation suppression approach to address CR's unsmooth distal end trajectory is proposed. Simulated experiments show that the CR autonomously completes intervention tasks with a smooth and stable trajectory, reducing distal end oscillation by over 45%. It achieves a target endpoint within the fourth level bronchus (approximately 5 mm diameter) with over 90% probability.

Analysis and suppression of offshore wind power broadband oscillation based on HVDC transmission technology

Analysis and suppression of offshore wind power broadband oscillation based on HVDC transmission technology

A Power-RPM Reduced-Order Model and Power Control Strategy of the Dual Three-Phase Permanent Magnet Synchronous Motor in a V/f Framework for Oscillation Suppression

A Power-RPM Reduced-Order Model and Power Control Strategy of the Dual Three-Phase Permanent Magnet Synchronous Motor in a V/f Framework for Oscillation Suppression

A novel reduced-order model reference adaptive control approach with high-frequency oscillation suppression

High-frequency oscillations may occur in the control signal when the adaptive gain is too large, which will adversely affect the robustness of the model reference adaptive control (MRAC) law and potentially induce system instability. To tackle this challenge, we introduce a reduced-order MRAC approach based on a modified scalar update law that includes a modification term to filter out high-frequency content for the multi-input multi-output (MIMO) nonlinear dynamical systems. This modification significantly reduces the high-frequency oscillations, allowing a controller with a high adaptive gain to achieve fast adaptation. In addition, with this reduced-order adaptive control approach, only two parameters need to be updated online, thus substantially reducing the overall computation burden. Furthermore, we demonstrate that the proposed reduced-order MRAC approach guarantees the Lyapunov asymptotic stability of the system error dynamics. Simulation results are conducted to validate the electiveness of the proposed method.

Experimental study of discharge current oscillations with dust particles

We present a detailed experimental study of discharge current oscillations in a planar cathode plasma with poly-dispersed alumina dust particles. The dominant frequency of oscillation depends on the discharge voltage, operating pressure, and amount of dust particles placed on the cathode. The power-law variation in the dominant frequency with different external operating parameters is presented. Experimental observations suggest that the dominant mechanism behind the generation of these oscillations is the cathode spot injection of sub-micron-sized dust particles. The cathode spots also aid in the generation of fine dust particles. The threshold limit on dust particle density dispersed on the cathode suggests that below the threshold limit, the fine particles depleting the electrons play an important role and lead to the generation of self-excited oscillations. Operating above the threshold limit, a stable dust cloud was observed together with the suppression of self-excited oscillations.

Real-type test platform capacitor bank switching oscillation suppression strategy and switching device design

Real-type test platform capacitor bank switching oscillation suppression strategy and switching device design

Grid-connected virtual synchronous generator transient suppression based on proportional differential control and frequency low-pass filtering

Abstract The virtual synchronous generator (VSG) technology has a wide range of applications in various distributed generation units. However, sudden changes in power command at grid connection can lead to severe oscillations in the output power and frequency of virtual synchronous generators. In addition, existing oscillation suppression methods are either based on complex parameter designs or change the original inertial support characteristics and power frequency drop characteristics. In this paper, a new transient suppression method is proposed, i.e., a proportional differential controller is added behind the power error and an additional low-pass filter is placed behind the output frequency. Finally, by establishing a simulation platform, it is verified that the proposed scheme can greatly reduce the overshoot, regulation time and frequency offset of the active power.