Research on LCL-type three-phase photovoltaic grid-connected inverter based on passive damping

The traditional LCL filter has resonance phenomenon in the working process of three-phase photovoltaic grid-connected inverter system. Based on the analysis of the frequency characteristics of LCL filter equivalent circuit before and after the introduction of passive damping resistor, it is concluded that the resonance of the system can be suppressed after the introduction of passive damping resistor. In the meantime, the current double closed-loop control strategy used in the system is introduced in detail. Finally, the simulation model is built by Matlab/Simulink simulation platform to verify the feasibility of the research method of LCL-type three-phase photovoltaic grid-connected inverter based on passive damping.

Vision Analysis of the Influence of Piezoelectric Energy Harvesting on Vibration Damping of a Cantilever Beam

A cantilever beam, manufactured from a steel-carrying substrate and two patches of Macro Fiber Composite of P2 type, was a subject of laboratory research. MFC patches were glued on both sides of the carrying substrate and were parallelly connected. An experimental determination of an optimal resistance for both energy harvesting and vibration passive damping of the cantilever beam was the purpose of the conducted laboratory research. The research contained 10 experiments in which courses of the energy-harvesting process and resistive passive damping of vibration were estimated. Energy harvesting was estimated by measurements of the generated current for the given load-resistance values. Resistive passive damping of vibration was assessed by using a vision method that enabled the displacements’ measurements of 10 selected points in the beam structure for the given shunt-resistance values. Values of both load resistance and shunt resistance were chosen on the basis of analytically calculated optimal load resistance and optimal shunt resistance. On the basis of the conducted experiments, the resistance range for which both the energy-harvesting process and the vibration-damping process are most effective was determined.

A quasi-two-dimensional finite element formulation for analysis of active-passive constrained layer beams

Active-passive damping is getting more popular with designers because it combines the complementary passive and active features in the control of structural vibrations. The classical three-layer structure has a viscoelastic-layer sandwiched between the host beam and a piezoelectric-layer. The more prevalent assumptions for modeling the system are the use of Euler-Bernoulli beam theory for both the host beam and piezoelectric-layer, and Timoshenko beam theory for the viscoelastic-layer. The assumption that transverse displacement is constant through the thickness limits accuracy and applicability of the model. The current formulation expresses the through-the-thickness dependency of the field variables as polynomials while their span dependency across a finite element is cubically interpolated. The versatility of the formulation is demonstrated via static and dynamic studies of examples taken from the literature. A beam treated with active-passive damping is presented and examined. The constitutive relation of the viscoelastic layer is represented using fractional derivatives and the Grünwald approximation. The extended Hamilton's principle is used to derive the system governing equations which are integrated with the Newmark time-integration system.

A quasi-two-dimensional finite element formulation for analysis of active-passive constrained layer beams

Active-passive damping is getting more popular with designers because it combines the complementary passive and active features in the control of structural vibrations. The classical three-layer structure has a viscoelastic-layer sandwiched between the host beam and a piezoelectric-layer. The more prevalent assumptions for modeling the system are the use of Euler-Bernoulli beam theory for both the host beam and piezoelectric-layer, and Timoshenko beam theory for the viscoelastic-layer. The assumption that transverse displacement is constant through the thickness limits accuracy and applicability of the model. The current formulation expresses the through-the-thickness dependency of the field variables as polynomials while their span dependency across a finite element is cubically interpolated. The versatility of the formulation is demonstrated via static and dynamic studies of examples taken from the literature. A beam treated with active-passive damping is presented and examined. The constitutive relation of the viscoelastic layer is represented using fractional derivatives and the Grünwald approximation. The extended Hamilton's principle is used to derive the system governing equations which are integrated with the Newmark time-integration system.

Shear actuation-based hybrid damping treatment of sandwich structures using a graphite particle-filled viscoelastic layer

In this work, the effectiveness of a shear actuation-based hybrid active-passive damping treatment is investigated by incorporating the inclusion of graphite particles within the viscoelastic damping layer. The study is performed through the flexural vibration analysis of a sandwich plate-strip where the core is made of a laminate of active layers and graphite particle-filled viscoelastic layers in two different stacking sequences. The active layers are comprised of shear mode piezoelectric actuator patches that are activated according to a shear-based velocity feedback control strategy. The analysis is performed by deriving a closed-loop finite element model of the sandwich plate-strip, and it reveals that the hybrid damping is significantly dependent on the stacking sequence of active and passive damping layers at the core. The inclusion of graphite particles not only provides augmented passive damping but also causes enhanced transfer of shear actuation force from the active layers to other layers. As a result, a significantly improved shear actuation-based hybrid active-passive damping is achieved due to the inclusion. The effectiveness of this hybrid damping in attenuation of resonant displacement-amplitude is also presented by configuring the volume fraction of graphite particles and shear actuator patches in an optimal manner.