Active Damper Frequency Division Control Method for Cluster Resonance of Photovoltaic Inverters

Aiming at the harmonic resonance problem of photovoltaic inverter cluster system when it is incorporated into weak power grid, an active damper frequency division control method is proposed to suppress the harmonic resonance. Firstly, the voltage signal measured by the voltage transformer is separated according to the frequency, and then the harmonic conductance value of the frequency band is controlled respectively according to the harmonic voltage. Finally, the output current is feedback controlled by the generalized integral PI controller, so as to realize the impedance remolding of the photovoltaic inverter cluster system. This method can adjust the value of virtual conductance in different frequency band adaptively according to the harmonic voltage, so as to suppress the harmonic resonance problem of photovoltaic inverter cluster more effectively. The simulation results of Matlab/Simulink demonstrate the correctness and effectiveness of the proposed frequency division control method.

Design of an Active Damping System for Vibration Control of Wind Turbine Towers

The vibration of wind turbine towers is relevant to the reliability of the wind turbine structure and the quality of power production. It produces both ultimate loads and fatigue loads threatening structural safety. This paper aims to reduce vibration in wind turbine towers using an active damper named the twin rotor damper (TRD). A single degree of freedom (SDOF) oscillator with the TRD is used to approximate the response of wind turbines under a unidirectional gusty wind with loss of the electrical network. The coincidence between the wind gust and the grid loss is studied to involve the maximum loading on the structure. The performance of the proposed damping system under the maximum loading is then evaluated on the state-of-the-art wind turbine NREL 5 MW. The effectiveness of the TRD is compared to a passive tuned mass damper (TMD) designed with similar requirements. The numerical results reveal that, at the 1st natural mode, the TRD outperforms the passive TMD by three to six times. Moreover, the results show that the TRD is effective in reducing ultimate loads on wind turbine towers.

Milling Processes with Active Damping: Modeling and Stability

Active dampers are on the verge of appearing in commercial machines as devices that assist the avoidance of machine tool chatter. The adjustment of control parameters in these devices is mostly guided by models that do not consider the dynamics within the control loop of active damper. Therefore, these models neglect the dynamics of actuation, measurement and filtering, which can result in inaccurate stability predictions that hinder the efficient tuning of active dampers. To formulate a more realistic model for milling processes assisted by active damping, this paper derives a novel mathematical model that takes into account the internal dynamics of the actuator, measuring device, and discrete filtering. This study shows that accurate stability prediction requires the incorporation of actuator and filter dynamics into the model, especially at high spindle speeds and large feedback gains.

FxLMS Algorithm for Active Vibration Control of Structure By Using Inertial Damper with Displacement Constraint

Engine is the main source of vibration that generates unwanted noise and vibration of vehicle chassis. Especially, in submarine applications, radiation of noise signatures can be detected at some distance away from the submarine using a sonar array. Thus quiet operation is crucial for submarine’s survivability. This study addresses reduction of the force transmissibility originating from engines and transmitted to hull through engine mounts. An inertial damper, as an actuator of hybrid mount system, is addressed to reduce even further the level of vibration. Narrow band FxLMS algorithms are broadly used to cancel the vibration of engine mount because of its excellent performance of canceling narrow band noise. However, in real active dampers, the maximum displacement of damper mass is kinematically restricted. When the control input signal from the FxLMS algorithm exceeds this limitation, the damper mass will collide with the mechanical stops and results in many problems. Originated from these, a modified narrow band FxLMS algorithm based on the equalizer technique with the maximum allowable displacement of active damper mass is proposed in this study. Some simulation results showed that the propose algorithm is effective to suppress vibration of engine mount while ensuring given displacement constraint.

Computational Framework of Various Semi-Active Control Strategies for Road Vehicles Thorough Bondgraphs

Vehicle suspension system plays a vital role in diminishing the vibration caused by the road roughness and prevent it from transmitting to the driver and the passenger. The semi-active suspensions contain spring and damping elements with variable properties, which can be changed by an external control. The work presented here is concerned with semi-active damper control for vibration isolation of base disturbances. Numerous control algorithms for semi active system had been suggested in the past, performed experimentally and validated with various computational models.In this work, the 2-DOF quarter car model with semi-active suspension, controlled by skyhook and balance logic with on-off and continuous control algorithms is being studied.The computational models are subjected to various road profiles like single half sine bump, random road disturbanceas typical Indian road scenario. So that the performance can be done as real time inputs. The simulation is being carried out on Matlab or Simulink.

Computational framework of Various Semi-active Control Strategies for Road Vehicles Thorough Bondgraphs

Vehicle suspension system plays a vital role in diminishing the vibration caused by the road roughness and prevent it from transmitting to the driver and the passenger. The semi-active suspensions contain spring and damping elements with variable properties, which can be changed by an external control. The work presented here is concerned with semi-active damper control for vibration isolation of base disturbances. Numerous control algorithms for semi active system had been suggested in the past, performed experimentally and validated with various computational models.In this work, the 2-DOF quarter car model with semi-active suspension, controlled by skyhook and balance logic with on-off and continuous control algorithms is being studied.The computational models are subjected to various road profiles like single half sine bump, random road disturbanceas typical Indian road scenario. So that the performance can be done as real time inputs. The simulation is being carried out on Matlab or Simulink.

Piezoelectric Active Damper for Surface Roughness Improvement in Hard Turning Processes

Surface roughness and profile accuracy on rolling or sliding surfaces are critical for the wear and fatigue of a component. A high roughness or poor profile accuracy results in higher friction and higher wear rate of the surface. One of the major factors affecting the surface roughness is chatter vibrations. This paper presents a novel design and development of an active damper for chatter suppression of hard turning processes using a piezoelectric actuator and strain signal for chatter detection. The active damper consists of a piezoelectric actuator with an embedded strain gauge for measuring the vibration displacement. In this work, the radial strain signal as a result of radial chatter vibrations from the strain gauge is used as a feedback signal to the actuator using a feedback controller. The experimental results showed a significant suppression in chatter vibrations and improvement of surface roughness using the proposed active damper. The details of the tool design, control design, hardware implementation and system validation are given hereinafter.