Optimal PID Tuning of PLL for PV Inverter Based on Aquila Optimizer

Phase-locked loop (PLL) is a fundamental and crucial component of a photovoltaic (PV) connected inverter, which plays a significant role in high-quality grid connection by fast and precise phase detection and lock. Several novel critical structure improvements and proportional-integral (PI) parameter optimization techniques of PLL were proposed to reduce shock current and promote the quality of grid connection at present. However, the present techniques ignored the differential element of PLL and did not acquire ideal results. Thus, this paper adopts Aquila optimizer algorithm to regulate the proportional-integral-differential (PID) parameters of PLL for smoothing power fluctuation and improving grid connection quality. Three regulation strategies (i.e., PLL regulation, global regulation, and step regulation) are carefully designed to systematically and comprehensively evaluate the performance of the proposed method based on a simulation model in MATLAB/Simulink, namely, “250-kW Grid-Connected PV Array”. Simulation results indicate that PLL regulation strategy can effectively decrease power fluctuation and overshoot with a short response time, low complexity, and time cost. Particularly, the Error(P) and the maximum deviation of output power under optimal parameters obtained by PLL strategy are decreased by 418 W and 12.5 kW compared with those under initial parameters, respectively.

Accurate Modeling of Working Normal Rake Angles and Working Inclination Angles of Active Cutting Edges and Application in Cutting Force Prediction

The normal Rake angle is an important geometric parameter of a turning tool, and it directly affects the accuracy of the cutting force prediction. In this study, an accurate model of the working normal rake angle (WNRA) and working inclination angle (WIA) is presented, including variation in the cutting velocity direction. The active cutting edge of the turning tool is discretized into differential elements. Based on the geometric size of the workpiece and the position of the differential elements, the cutting velocity direction of each differential element is calculated, and analytical expressions for the WNRA, WIA, and working side cutting edge angle are obtained for each differential element. The size of the workpiece is found to exert an effect on the WNRA and WIA of the turning tool. The WNRA and WIA are used to predict the cutting force. A good agreement between the predicted and experimental results from a series of turning experiments on GH4169 with different cutting parameters (cutting depth and feed rate) demonstrates that the proposed model is accurate and effective. This research provides theoretical guidelines for high-performance machining.

INFORMATION SYSTEM OF THE TEST BENCH FOR DRIVING GAS TURBINE ENGINES

This article studies the problem of determining the technical condition of drive and energetic gas turbine engines (GTE) during acceptance tests that have been repaired at a specialized enterprise. The following descriptions are given: of the bench for testing drive and energetic gas turbine engines; of the bench systems for monitoring and measurement, methods for conducting acceptance tests; of the evaluation the quality of the repaired engine based on its thermogasdynamics parameters; of the processing of measurement results obtained during acceptance tests. The materials of the system of differential (subassembly) diagnostics of GTE are generalized. The authors have considered the features of diagnostics of transient modes of GTE. The authors suggest the transition from the engine node to its elements as one of the ways to further improve the differential diagnostics, which has required developing the technique and system of pressure and temperature measurement at inlet and outlet of stage axial compressor. An algorithm for differential (element-by-element) engine diagnostics is described using the example of an axial compressor stage.

Axial profiles of heat transfer coefficients in a liquid film evaporator

Regeneration is the most efficient way of managing used oil. It saves money by preventing costly clean-ups and liabilities associated with mismanagement of used oil and it also helps to protect the environment. A numerical study of the flow, heat and mass transfer characteristics of the vertical evaporating tube with the films flowing down on both the inside and the outside tube surfaces has been carried out. Condensation occurs along the outside wall surface and evaporation at the free surface of the inside film. The calculation domain of two film flow regions and tube wall is solved simultaneously. The longitudinal variation of temperature, mass flow rate, and hence the thickness of the films downward the tube can be obtained by applying conservation of the energy requirement to the differential element.

Research on Electro-Hydraulic Force Servo Control System Based on Specialist PID Control Strategy

There is flexibility load in the electro-hydraulic force servo control system researched in this paper, and it results in that there is a lower oscillation frequency secondary differential element in radical of the transmit function of the system. The flexibility load and the secondary differential element seriously impact the bandwidth of the system and let the bandwidth rise difficultly, and that the flexibility load and the secondary differential element make the system oscillation even instability easily. Aiming at this special characteristic and the smaller system gain characteristic of the electrohydraulic force servo control system, the specialist PID control theory applied to the electro-hydraulic force servo control system which is the typical nonlinear system. The mathematic model of the system is built and the simulation and the experiment research is finished in the work of this paper, at the same time, the author of this paper compares the control result of the new controller designed according to the specialist PID control theory with the control result of traditional PID controller. The simulation and the experiment results indicate that the new controller designed according to the specialist PID control theory not only enlarge the bandwidth of system, improve the accuracy, reduce control error, but also accelerate the response speed obviously, increase the dynamic property of the system.

On the Modeling and Experimental Validation of Multi-Field Polymer-Based Bimorphs

Origami — the Japanese art of folding — has inspired various engineering applications for several decades due to its ability to manipulate complex shapes. In our study, multi-field actuated self-folding Origami structures are developed with the implementation of two classes of smart materials: relaxor ferroelectric polymers and magneto-active elastomers (MAEs). The chosen relaxor ferroelectric is P(VDF-TrFE-CTFE), a P(VDF)-based terpolymer and the MAE is a PDMS substrate with embedded barium hexaferrite particles. At the macroscale, this study involves the modeling of the large deformation of a bimorph comprising the aforementioned magnetically and electrically actuated materials using a 1D analytical model derived from the equilibrium of a differential element. The large deformation is extracted from curvatures solved at each point for the resulting differential equation of the equilibrium state. On the microscale, this study also considers the nonlinear behavior of the smart materials. The nonlinear dielectric response of the relaxor ferroelectric polymer is captured by an electric field-dependent electrostrictive coefficient derived from a microstructure-based energy balance for the electrostriction of the terpolymer. The energy density function is postulated to be composed of an elastic contribution described by the Arruda-Boyce hyperelastic model and an electric contribution based on dipole-dipole interactions. On the other hand, a magnetic field-dependent torque drives the actuation of the MAEs, which is also dependent on the orientation of the material to the field. The integration of the micro and macro components results in an analytical model of a 1D, multi-layered flat structure that can be numerically solved for displacements under combined fields. The model is compared with well-matching experimental results of a unimorph and a bimorph structure as validation. The experiments measured the tip displacement of the beam under combined fields for a quantitative analysis. The study takes the analysis further by optimizing parameters such as geometry, field strengths, and the combination of active layers for relevant target shapes.

Corrosion Damage Investigation of Silver-Soldered Stainless Steel Orthodontic Appliances Used in Vivo / Ocena Zniszczeń Korozyjnych Używanych In Vivo Stałych Aparatów Ortodontycznych O Połączeniach Lutowanych Na Bazie Srebra

Processes of destruction of products used in orthodontic treatment, e.g. fixed orthodontic appliances, microimplants or dental prostheses considerably limit its operational lifetime and comfort and safety of patients. The objective of the research was to evaluate and assess corrosion damage to silver-soldered stainless steel rapid palatal expansion Hyrax devices. Used in vivo for 2 or 6 months, respectively, RPE (rapid palatal expansion) devices were analyzed macroscopically and in a scanning electron microscope with an energy X-ray analyzer for signs of corrosion. The evaluated appliances showed discernible differences between the overall condition of the noble solders and the stainless steel elements. The Ag-rich solders were chiefly covered in corrosion pits, whereas stainless steel wires, molar bands and Hyrax screws presented corrosion-free surfaces. What is more, the EDS analysis showed differential element composition of the solders. According to the results, noble materials, such as Ag-rich solders, can corrode in a salivary environment when coupled with stainless steel. The selective leaching processes are observed.