Two-leg three-phase inverter control for STATCOM and SSSC applications

Flexible ac transmission systems (FACTS) devices are attracting an increasing interest both in power system academic research and in electric utilities for their capabilities to improve steady-state performance as well as system stability. Several converter topologies for FACTS applications have been proposed in the recent literature, even if those based upon voltage source inverters (VSI) seem to be more attractive due to their intrinsic capability to rapidly respond to network changes such as perturbations subsequent to a fault and their property of being immune to resonance problem. In this paper, a new topology for inverter-based FACTS is proposed. This configuration, employing a two-leg three-phase inverter is employed for both series and parallel-connected reactive power compensators. The converter utilizes a modular topology for allowing a satisfaction of electronic components rating. A control strategy based on variable structure control technique with sliding mode is employed to track appropriate reference quantities. Design and control, as well as good tracking performances, are also verified through numerical simulations

Integral sliding-mode controller for maximum power point tracking in the grid-connected photovoltaic systems

The output power generated in the photovoltaic modules depends both on the solar radiation and the temperature of the solar cells. To maximize the efficiency of the system, it is required to monitor the maximum power point of the photovoltaic system. For this purpose, monitoring the maximum power point (MPPT) of photovoltaic systems should be as quick and accurately as possible for increasing energy production, which ultimately increases the cost-efficiency of the photovoltaic system. This paper proposes a new approach for MPPT) using the concept of the integral sliding mode controller (ISMC) to ensure fast and precise monitoring of the peak power. The performance of the ISMC is significantly influenced by the choice of the sliding surface. To assess the reliability ISMC control, the results have been compared with those of a PI controller. The results obtained are used to evaluate the performance of the ISMC strategy under different climatic conditions. Finally, the effectiveness of the proposed solution is confirmed using simulations in PSIM tools and experimental results were used to evaluate the effectiveness of the proposed approach

Comfort-Centered Design of a Lightweight and Backdrivable Knee Exoskeleton

This paper presents design principles for comfort-centered wearable robots and their application in a lightweight and backdrivable knee exoskeleton. The mitigation of discomfort is treated as mechanical design and control issues and three solutions are proposed in this paper: 1) a new wearable structure optimizes the strap attachment configuration and suit layout to ameliorate excessive shear forces of conventional wearable structure design; 2) rolling knee joint and double-hinge mechanisms reduce the misalignment in the sagittal and frontal plane, without increasing the mechanical complexity and inertia, respectively; 3) a low impedance mechanical transmission reduces the reflected inertia and damping of the actuator to human, thus the exoskeleton is highly-backdrivable. Kinematic simulations demonstrate that misalignment between the robot joint and knee joint can be reduced by 74% at maximum knee flexion. In experiments, the exoskeleton in the unpowered mode exhibits 1.03 Nm root mean square (RMS) low resistive torque. The torque control experiments demonstrate 0.31 Nm RMS torque tracking error in three human subjects.Comment: 8 pages, 16figures, Journa

Cascade sliding mode maximum power point tracking controller for photovoltaic systems

Introduction. Constant increases in power consumption by both industrial and individual users may cause depletion of fossil fuels and environmental pollution, and hence there is a growing interest in clean and renewable energy resources. Photovoltaic power generation systems are playing an important role as a clean power electricity source in meeting future electricity demands. Problem. All photovoltaic systems have two problems; the first one being the very low electric-power generation efficiency, especially under low-irradiation states; the second resides in the interdependence of the amount of the electric power generated by solar arrays and the ever changing weather conditions. Load mismatch can occur under these weather varying conditions such that maximum power is not extracted and delivered to the load. This issue constitutes the so-called maximum power point tracking problem. Aim. Many methods have been developed to determine the maximum power point under all conditions. There are various methods, in most of them based on the well-known principle of perturb and observe. In this method, the operating point oscillates at a certain amplitude, no matter whether the maximum power point is reached or not. That is, this oscillation remains even in the steady state after reaching the maximum power point, which leads to power loss. This is an essential drawback of the previous method. In this paper, a cascade sliding mode maximum power point tracking control for a photovoltaic system is proposed to overcome above mentioned problems. Methodology. The photovoltaic system is mainly composed of a solar array, DC/DC boost converter, cascade sliding mode controller, and an output load. Two sliding mode control design strategies are joined to construct the proposed controller. The primary sliding mode algorithm is designed for maximum power point searching, i.e., to track the output reference voltage of the solar array. This voltage is used to manipulate the setpoint of the secondary sliding mode controller, which is used via the DC-DC boost converter to achieve maximum power output. Results. This novel approach provides a good transient response, a low tracking error and a very fast reaction against the solar radiation and photovoltaic cell temperature variations. The simulation results demonstrate the effectiveness of the proposed approach in the presence of environmental disturbances.Вступ. Постійне збільшення енергоспоживання як промисловими, так і індивідуальними користувачами може призвести до виснаження запасів викопного палива та забруднення навколишнього середовища, тому зростає інтерес до чистих та відновлюваних джерел енергії. Фотоелектричні системи виробництва електроенергії відіграють важливу роль як екологічно чисте джерело електроенергії для задоволення майбутніх потреб в електроенергії. Проблема. Усі фотоелектричні системи мають дві проблеми; по-перше, дуже низька ефективність вироблення електроенергії, особливо в умовах низького опромінення; друга полягає у взаємозалежності кількості електроенергії, що виробляється сонячними батареями, та постійно мінливих погодних умов. У цих погодних умовах, що змінюються, може відбутися невідповідність навантаження, так що максимальна потужність не буде витягнута і передана в навантаження. Ця проблема є так званою проблемою відстеження точки максимальної потужності. Мета. Було розроблено безліч методів визначення точки максимальної потужності за будь-яких умов. Існують різні методи, здебільшого засновані на відомому принципі збурення та спостережень. У цьому методі робоча точка коливається з певною амплітудою, незалежно від того, досягнуто точку максимальної потужності чи ні. Тобто це коливання залишається навіть у стійкому стані після досягнення точки максимальної потужності, що призводить до втрати потужності. Це значний недолік попереднього способу. У цій статті для подолання вищезазначених проблем пропонується каскадне керування відстеженням точки максимальної потужності в режимі ковзання для фотоелектричної системи. Методологія. Фотоелектрична система в основному складається з сонячної батареї, перетворювача постійного струму, що підвищує, каскадного контролера ковзного режиму та вихідного навантаження. Дві стратегії проєктування керування ковзним режимом об'єднані для побудови пропонованого контролера. Алгоритм первинного ковзного режиму призначений для пошуку точки максимальної потужності, тобто для відстеження вихідної опорної напруги сонячної батареї. Ця напруга використовується для управління уставкою вторинного контролера ковзного режиму, який використовується через перетворювач постійного струму, що підвищує, для досягнення максимальної вихідної потужності. Результати. Цей новий підхід забезпечує хорошу перехідну характеристику, низьку помилку відстеження та дуже швидку реакцію на сонячне випромінювання та коливання температури фотогальванічного елемента. Результати моделювання демонструють ефективність пропонованого підходу за наявності збурень довкілля

Recent advances on recursive filtering and sliding mode design for networked nonlinear stochastic systems: A survey

Copyright © 2013 Jun Hu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Some recent advances on the recursive filtering and sliding mode design problems for nonlinear stochastic systems with network-induced phenomena are surveyed. The network-induced phenomena under consideration mainly include missing measurements, fading measurements, signal quantization, probabilistic sensor delays, sensor saturations, randomly occurring nonlinearities, and randomly occurring uncertainties. With respect to these network-induced phenomena, the developments on filtering and sliding mode design problems are systematically reviewed. In particular, concerning the network-induced phenomena, some recent results on the recursive filtering for time-varying nonlinear stochastic systems and sliding mode design for time-invariant nonlinear stochastic systems are given, respectively. Finally, conclusions are proposed and some potential future research works are pointed out.This work was supported in part by the National Natural Science Foundation of China under Grant nos. 61134009, 61329301, 61333012, 61374127 and 11301118, the Engineering and Physical Sciences Research Council (EPSRC) of the UK under Grant no. GR/S27658/01, the Royal Society of the UK, and the Alexander von Humboldt Foundation of Germany

Improved direct torque control using Kalman filter: application to a doubly-fed machine

Direct Torque Control (DTC) has been extensively researched and applied during the last two decades. However, it has only first been applied to the Brushless Doubly Fed Reluctance Machine (BDFRM) a few years ago in its basic form inheriting its intrinsic flux estimation problems that propagate throughout the algorithm and hence compromise the DTC performance. In this paper, we propose the use of Kalman Filter (KF) as an alternative to improve the estimation and consequently the control performance of the DTC. The KF is designed around a nominal model, but is shown to be reliable over the whole operating range of the BDFRM. Moreover, we use a modified robust exact differentiator based on Sliding Mode (SM) techniques to calculate the angular velocity from an angular position encoder. Computer simulations are meticulously designed to take into account real-world physical constraints and thus show illustrative supporting results as expected from an experimental setup

Multi-Input Single-Inductor MPPT Regulator with Sliding-Mode Controller

abstract: A Multi-input single inductor dual-output Boost based architecture for Multi-junction PV energy harvesting source is presented. The system works in Discontinuous Conduction Mode to achieve the independent input regulation for multi-junction PV source. A dual-output path is implemented to regulate the output at 3V as well as store the extra energy at light load condition. The dual-loop based sliding-mode MPPT for multi-junction PV is proposed to speed up the system response time for prompt irradiation change as well as maximize MPPT efficiency. The whole system achieves peak efficiency of 83% and MPPT efficiency of 95%. The whole system is designed, simulated in Cadence and implemented in PCB platform.Dissertation/ThesisMasters Thesis Electrical Engineering 201

The kinematics of hyper-redundant robot locomotion

This paper considers the kinematics of hyper-redundant (or “serpentine”) robot locomotion over uneven solid terrain, and presents algorithms to implement a variety of “gaits”. The analysis and algorithms are based on a continuous backbone curve model which captures the robot's macroscopic geometry. Two classes of gaits, based on stationary waves and traveling waves of mechanism deformation, are introduced for hyper-redundant robots of both constant and variable length. We also illustrate how the locomotion algorithms can be used to plan the manipulation of objects which are grasped in a tentacle-like manner. Several of these gaits and the manipulation algorithm have been implemented on a 30 degree-of-freedom hyper-redundant robot. Experimental results are presented to demonstrate and validate these concepts and our modeling assumptions