Standalone power supplies using renewable energy resources become a key solution to address both energy consumption and environmental restrictions in remote locations. These standalone systems are weak low-voltage networks, wherein the presence of heavy non-linear and/or unbalanced loads may adversely affect the output voltage quality. Accordingly, four-leg voltage-source inverters play an important role by providing both balanced and unbalanced loads with clean power and balanced output voltage. The reported work proposes a sliding mode control (SMC) along with an iterative learning control (ILC) for harmonic compensation in the presence of critical load conditions such as unbalanced non-linear loads. Indeed, under substantial disturbances, the ILC harmonic compensator smoothly adjusts the input control signal of the SM controller in such a manner to properly reject the disturbing harmonics. The design methodology of the proposed SMC-ILC control scheme is detailed and its effectiveness is validated through simulation and experimental results.
The design of an offshore wind turbine (OWT) founded on a monopile foundation is principally based on dimensioning criteria related to its fundamental frequencies.These frequencies must remain outside the excitation frequencies to avoid resonance. For the calculation of the OWT natural frequencies, several studies exist, but few of them simultaneously consider both the real geometrical configuration of the OWT superstructure (tower, blades, and transition piece) and the three-dimensional (3D) soil domain and its interaction with the monopile foundation. This paper aims at filling this gap. A rigorous 3D finite element method-based model of a 10 MW DTU OWT installed in sand is developed. The aim is to perform a structural modal analysis of the wind turbine in parked condition. The obtained natural frequencies are compared with those corresponding to other simplified models available in literature for the foundation and the superstructure in the scope of giving an insight about how poorly the existing simplified models can predict the OWT natural frequencies.Finally, a parametric analysis is performed to study the effect of the water depth, the monopile dimensions (diameter, thickness, and embedded depth), the transition piece height, and the sandy soil relative density on the system natural frequencies.
International audienceThe objective is to design a fully automated glycemia regulation of Type-1 Diabetes (T1D) in both fasting and postprandial phases on a large number of virtual patients. A model-free intelligent PID (iPID) is used to infuse insulin. The feasibility is tested in silico on two simulators with and without measurement noise. The first simulator is derived from a long-term linear time-invariant model. The controller is also validated on the UVa/Padova metabolic simulator on 10 adults under 25 runs/subject for noise robustness test. It is shown that without measurement noise, iPID mimicked the normal pancreatic secretion: a fast rate occurs immediately after meals; it becomes moderate when glycemia decays and reduces to a steady basal mode during fasting. With the UVa/Padova simulator, the robustness against CGM noise and delays was tested. A higher percentage of time in target was obtained with iPID as compared to standard PID with reduced time spent in hyperglycemia.Two different T1D simulators tests showed that iPID detects meals and reacts faster to meal perturbations as compared to a classic PID. The intelligent part turns the controller to be more aggressive immediately after meals without neglecting safety. Thus, postprandial hyperglycemia is reduced with less late postprandial hypoglycemia. The simple structure iPID is a step for PID like controllers since it combines the classic PID nice properties with new adaptive features
This paper presents an advanced control strategy for power quality enhancement in standalone power-supply systems (PSSs) with grid forming Four-Leg Voltage Source Inverters (FL-VSIs). Indeed, an online Adaptive Reference Generator (ARG) with a Grey Wolf Optimizer (GWO) is proposed to sustain the control performances of a Feedback Linearization Control (FLC) strategy and improve its robustness against load side disturbances and system parameters uncertainties. The key purpose of the proposed GWO based ARG is to compensate for load and phase disturbances through smooth reference adjustments, in order to improve voltage waveforms quality and symmetry and conform to the existing power quality standards and metrics. The design methodology of the proposed control approach is thoroughly detailed, and its effectiveness is asserted through Simulation and Experimental tests, demonstrating its superiority in maintaining the voltage waveforms within the required standard limitations even under unbalanced and nonlinear loading conditions.
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