On Adaptive Moving Average Algorithms for the Application of the Conservative Power Theory in Systems with Variable Frequency

The Conservative Power Theory (CPT) emerged in recent decades as a theoretical framework for coping with harmonically distorted and unbalanced electric networks of ac power systems with a high participation of converter interfaced loads and generation. The CPT measurements are intrinsically linked to moving averages (MA) over one period of the grid. If the CPT is to be used in a low-inertia isolated-grid scenario, which is subjected to frequency variations, adaptive moving averages (AMA) are necessary. This paper reviews an efficient way of computing MAs and turns it into an adaptive one. It shows that an easily available variable time delay block, from MATLAB, causes steady-state errors in the measurements when the grid frequency varies. A new variable time delay block is, thus, proposed. Nonetheless, natural pulsations in the instantaneous power slip through MAs when the discrete moving average window does not fit perfectly the continuously varying period of the grid. A method consisting of weighing two MAs is reviewed and a new and effective hybrid AMA is proposed. The CPT transducers with the different choices of AMAs are compared via computer simulations of a single-phase voltage source feeding either a linear or a nonlinear load.

Design of a Functional H Filter for Linear Singular Systems With an Additional Unknown Input, Bounded Disturbance, and Variable Time Delay

This paper deals with a new method for the design of a functional filter for linear singular systems with bounded disturbance and variable time delay in the state and the known input vectors. Moreover, a disturbance unknown inputs is considered. The main objective of such design is the estimation of functional state vector, and a part of the disturbance unknown inputs for fault detection. The proposed design is based on Lyapunov-Krasovskii stability theory and, in order to minimize the disturbance effect, the designed filter satisfies a H_∞ criterion. Numerical simulation is used to illustrate the proposed design and the results were successful.

Механизм формирования наноструктур гексагональной симметрии на поверхности металлов последовательностью сдвоенных ультракоротких импульсов излучения ортогональной поляризации

An experimental results causing the ordered hexagonal symmetry surface nanostructures formation on metals under the sequence of scanned doubled collinear femtosecond pulses of orthogonal polarization and variable time-delay have been analized. It was shown that the structures production caused by the dynamic grating formation by the first pulse, excitation of two paires of surface plasmon polaritons in symmetric to the polarization vector directions of second pulse directions with 60 degrees angle between formed respective dynamic gratings and forth-fold first grating degeneration. So three gratings of three-flold symmetry about surface normal creates experimentally observable resonant surface relief of hexagonal symmetry.

The Effect of Time Delay on 3D Printed Part Strength

We are investigating the impact on 3D printed part strength when the extruder is positioned using articulated robotic arms in place of a traditional x-y gantry-style system. One of our printer designs is called the DeXter printer [1] which uses two selective compliance assembly robotic arms (SCARA) to position dual extruders. An advantage of using dual robotic arms is that two extruders can move independently drastically reducing build times, or the second arm can perform additional operations like segment stimulation during the build process [2]. In either case the arms require a collision avoidance process to prevent them from colliding in the part space. A possible drawback of the collision avoidance requirement is that it can result in a time delay along some sections of the layer which, due to cooling, could have adverse effects on the part strength. This research aims to determine how this cooling time will affect the strength of ABS extruded parts. We performed tensile tests on 3D printed part samples for which we altered the g-code to produce a variable time delay during the printing process. Our control sample had a zero-dwell time, and as we increased dwell time we found that the ultimate tensile strength (UTS) did decrease.