101 research outputs found

    PID control system analysis and design

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    With its three-term functionality offering treatment of both transient and steady-state responses, proportional-integral-derivative (PID) control provides a generic and efficient solution to realworld control problems. The wide application of PID control has stimulated and sustained research and development to "get the best out of PID", and "the search is on to find the next key technology or methodology for PID tuning". This article presents remedies for problems involving the integral and derivative terms. PID design objectives, methods, and future directions are discussed. Subsequently, a computerized, simulation-based approach is presented, together with illustrative design results for first-order, higher order, and nonlinear plants. Finally, we discuss differences between academic research and industrial practice, so as to motivate new research directions in PID control

    Back calculation Anti Windup PID controller on Several Well-Known Tuning Method for Glycerin Bleaching Process Temperature Regulation

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    The aim of this paper is to comprehend the performance of back calculation anti windup scheme with difference tracking time constant, Ta on Proportional – Integral - Derivative (PID) controller for improving temperature regulation of glycerin bleaching process.  Several available well tuning methods including Ziegler Nichols (ZN), Internal Model Control (IMC) and Integral Square Error (ISE)-Load are used and analyzed. The performance of the controller tuning methods are  compared based on percentage of overshoot, settling time, rise time and time to recovery on the presence of disturbance. From the results, the best performance of temperature regulation for glycerin bleaching process can be reached by using ISE-Load tuning with tracking time constant, Ta equal to derivative time constant, Td.&nbsp

    Robust Voltage Vector-Controlled Three-Phase SAPF-based BPMVF and SVM for Power Quality Improvement

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    The multiplication of nonlinear loads leads to significant degradation of the energy quality, thus the interconnection network is subject to being polluted by the generation of harmonic components and reactive power, which causes a weakening efficiency, especially for the power factor. In three-phase systems, they can cause imbalances by causing excessive currents at the neutral. This research treats the operation of robust voltage-oriented control (VOC) for a shunt active power filter (SAPF). The main benefit of this technique is to guarantee a decoupled control of the active and reactive input currents, as well as the input reference voltage. To sustain the DC voltage, a robust PI-structure-based antiwindup is inserted to ensure active power control. Besides, a robust phase-locked loop (PLL)-based bandpass multivariable filter (BPMVF) is used to improve the network voltage quality. Furthermore, a space vector modulation (SVM) is designed to replace the conventional one. A sinusoidal network current and unitary power factor are achieved with fewer harmonics. The harmonics have been reduced from 27.98% to 1.55% which respects the IEEE 519-1992 standard. Expanded simulation results obtained from the transient and steady-state have demonstrated the high performance of the suggested control scheme

    Low-gain Integral Control for Multi-Input, Multi-Output Linear Systems with Input Nonlinearities

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    We consider the inclusion of a static anti-windup component in a continuous-time low-gain integral controller in feedback with a multi-input multi-output stable linear system subject to an input nonlinearity (from a class of functions that includes componentwise diagonal saturation). We demonstrate that the output of the closed- loop system asymptotically tracks every constant reference vector which is “feasible” in a natural sense, provided that the integrator gain is sufficiently small. Robustness properties of the proposed control scheme are investigated and three examples are discussed in detail

    Centralized Airflow Control to Reduce Output Power Variation in a Complex OWC Ocean Energy Network

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    A centralized airflow control scheme for a complex ocean energy network (OEN) is proposed in this paper to reduce the output power variation (OPV). The OEN is an integrated network of multiple oscillating water columns (OWCs) that are located at different geographical sites connected to a common electrical grid. The complexity of the OWC-OEN increases manifolds due to the integration of several OWCs and design of controllers become very challenging task. So, the centralized airflow control scheme is designed in two stages. In control stage-1, a proportional-integral- (PI-) type controller is designed to provide a common reference command to control stage-2. In control stage-2, the antiwindup PID controllers are implemented for the airflow control of all the OWCs simultaneously. In order to tune the large number of control parameters of this complex system, a fitness function based on integral squared error (ISE) is minimized using the widely adopted particle swarm optimization (PSO) technique. Next, the simulation results were obtained with random wave profiles created using the Joint North Sea Wave Project (JONSWAP) irregular wave model. The OPV of the proposed OWC-OEN was reduced significantly as compared to the individual OWC. It was further observed that the OPV of the proposed scheme was lower than that achieved with uncontrolled and MPPT controlled OWC-OEN. The effect of communication delay on the OPV of the proposed OWC-OEN scheme was also investigated with the proposed controller, which was found to be robust for a delay up to 100 ms.This work was supported in part by the Basque Government through project IT1207-19 and MCIU/MINECO through RTI2018-094902-B-C21/RTI2018-094902-B-C22 (MCIU/AEI/FEDER, UE)

    Control Strategies for Open-End Winding Drives Operating in the Flux-Weakening Region

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    This paper presents and compares control strategies for three-phase open-end winding drives operating in the flux-weakening region. A six-leg inverter with a single dc-link is associated with the machine in order to use a single energy source. With this topology, the zero-sequence circuit has to be considered since the zero-sequence current can circulate in the windings. Therefore, conventional over-modulation strategies are not appropriate when the machine enters in the flux-weakening region. A few solutions dealing with the zero-sequence circuit have been proposed in literature. They use a modified space vector modulation or a conventional modulation with additional voltage limitations. The paper describes the aforementioned strategies and then a new strategy is proposed. This new strategy takes into account the magnitudes and phase angles of the voltage harmonic components. This yields better voltage utilization in the dq frame. Furthermore, inverter saturation is avoided in the zero-sequence frame and therefore zero-sequence current control is maintained. Three methods are implemented on a test bed composed of a three-phase permanent-magnet synchronous machine, a six-leg inverter and a hybrid DSP/FPGA controller. Experimental results are presented and compared for all strategies. A performance analysis is conducted as regards the region of operation and the machine parameters.Projet SOFRACI/FU

    multiclass aQM on a tCP/IP router: a control theory approach

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    Producción CientíficaActive queue management (AQM) is a well-known technique to improve routing performance under congested traffic conditions. It is often deployed to regulate queue sizes, thus aiming for constant transmission delay. This work addresses AQM using an approach based on control theory ideas. Compared with previous results in the literature, the novelty is the consideration of heterogeneous traffic, ie, multiclass traffic. Thus, each traffic class may have different discarding policies, queue sizes, and bandwidth share. This feature brings the proposal nearer to real network management demands than previous approaches in the literature. The proposed technique assumes that each class already has a simple controller, designed a priori, and focuses on designing a static state-feedback controller for the multiclass system, where the design is based on using LMIs for the calculations. For this, optimization problems with LMI constraints are proposed to compute the state-feedback gains that ensure stability for a large set of admissible initial conditions. These conditions ensure not only closed-loop stability but also some level of performance. As far as we know, this is the first control theory based approach for the AQM problem on TCP/IP routers that allows a multiclass AQM while also considering time-varying delays and input saturation. This is an important step to frame AQM in a more formal, yet realistic context, enabling it to address important service level agreement (SLA) directives. The proposal is tested on a simulated system at the end of this paper, showing the feasibility and performance of the approach in the presence of multiclass traffic.Junta de Castilla y León y FEDER. Grant Numbers: CLU 2017-09, UIC 23

    Contributions to the multi-frequency control of gridtied voltage source converters

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    El interés por la producción de energía limpia está en aumento y la generación de este tipo de energía se puede fomentar mediante la instalación de generadores locales. Dichos generadores son conectados a la red de distribución a través de convertidores de potencia. Al mismo tiempo el número de cargas conectadas a la red está incrementando y con ello el número de cargas no lineales. Estas últimas consumen corrientes armónicas y esto provoca distorsión armónica a la red. En esta tesis se estudia y se presentan contribuciones en el control de los convertidores de potencia para que al mismo tiempo que se inyecta potencia, el convertidor sea capaz de actuar adecuadamente frente a la distorsión armónica del voltaje de la red (control multifrecuencial). En primer lugar, esta tesis cubrirá el estudio de las diferentes técnicas de control de corrientes armónicas y también de las diferentes técnicas de sincronización y detección de componentes armónicas de tensión presentes en la red. En cuanto al cálculo de referencias de corrientes armónicas, se explican las principales variantes dependiendo de la funcionalidad deseada y se estudia la entrega de potencia instantánea constante incluso con red distorsionada. Además, se propone un nuevo método de cálculo para eliminar las principales oscilaciones de potencia sin exceder las limitaciones de distorsión de corrientes. También se describen las limitaciones del convertidor cuando se trabaja con componentes fundamentales y armónicas. Se analizan los principales saturadores multifrecuenciales para evitar la sobremodulación y se propone un nuevo saturador que no empeora la dinámica total del sistema y siempre consigue el mínimo THD de corriente. Por último, se aborda la problemática de la distorsión armónica del voltaje de red. Primero se estudia la compensación de las corrientes consumidas por cargas locales y después se propone la compensación directa de la tensión del PCC. En esta tesis se intenta incrementar el número de funcionalidades que puede desempeñar el convertidor para que además de entregar potencia, sea capaz de mejorar la calidad de la red, sin exceder las limitaciones físicas del convertidor. Cada una de las contribuciones es validada mediante resultados de simulación y experimentales
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