A bridge between robustness and simplicity: practical control design for complex systems

Automatic control design has been one of the major subjects in real-world system design/operation and is becoming much more significant today in accordance with increasing size, changing structure, uncertainties and complexity of artificial industry systems. A major challenge in a new environment is to integrate computing, communication and control into appropriate levels of real-world systems operation and control. In practice, many control systems usually track different control objectives such as stability, disturbance attenuation and reference tracking with considering practical constraints, simultaneously. At the moment in the industry applications, it is desirable to meet all specified goals using the controllers with simple structures. Since, practically these controllers are commonly designed based on experiences, classical and trial-and-error approaches, they are incapable of obtaining good dynamical performance to capture all design objectives and specifications for a wide range of operating conditions and various disturbances. It is significant to note that because of using simple structure, pertaining to the low-order control synthesis for dynamical systems in the presence of strong constraints and tight objectives are few and restrictive. Under such conditions, the synthesis process may not approach to a strictly feasible solution. Therefore, the most of robust and optimal approaches suggest complex state-feedback or high-order dynamic controllers. Moreover in the most of proposed approaches, a single performance criterion has been used to evaluate the robustness of resulted control systems. This research addresses three systematical, fast and flexible algorithms to design of low order or static output controllers for dynamical systems. The developed strategies attempt to invoke the strict conditions and bridge the gap between the power of optimal/robust control theory and industrial control design. To illustrate the effectiveness of the proposed control strategies, they have been applied to several complex systems in the electric industry

The Japanese Clinical Practice Guideline for acute kidney injury 2016

Acute kidney injury (AKI) is a syndrome which has a broad range of etiologic factors depending on different clinical settings. Because AKI has significant impacts on prognosis in any clinical settings, early detection and intervention are necessary to improve the outcomes of AKI patients. This clinical guideline for AKI was developed by a multidisciplinary approach with nephrology, intensive care medicine, blood purification, and pediatrics. Of note, clinical practice for AKI management which was widely performed in Japan was also evaluated with comprehensive literature search

Robust Load Frequency Regulation In a New Distributed Generation Environment

A new approach based on μ-synthesis technique is proposed for the design of robust load frequency controller in response to the new technical demand for load frequency regulation in a competitive distributed generation power system. The siting of numerous generator units in distribution feeders is being encouraged by the current deregulation of the industry is likely to have an impact on the Load Frequency Control (LFC) operation of the existing power systems. In this approach the overall power system will be divided to some distribution areas. Each area is modeled as a collection of distributed generators to supply the area-load. The area is responsible to perform its own LFC by using an independent robust controller. An example for a distribution area is given to illustrate the proposed approach. The resulting controller is shown to minimize the effect of disturbances and achieve acceptable frequency regulation in presence of uncertainties and load variation

Robust low-order load frequency controller in a deregulated environment

The electric power industry is in transition from large and regulated utilities to an industry that will incorporate competitive companies selling unbundled power at lower rates. The new structure of electric power systems, which includes separate companies with an open access policy demands novel control strategies to maintain the stability and eliminates the frequency error. Under current organization several approaches have already been proposed. This paper addresses the design and introduce of reduced load frequency controller based on μ-synthesis theorem for a possible structure in the new deregulated open access environment. We used the singular values of the observability matrix of the high order μ-controller for reducing the controller order

Robust AGC in a competitive environment

A decentralized robust approach is proposed for an automatic generation control (AGC) system based on a generalized AGC structure. This work addresses a new strategy to adapt a well-tested classical AGC scheme to the changing environment of power system operation under deregulation. The effect of bilateral contracts is taken into account in each control area dynamical model as a set of new input signals. The PI-based AGC synthesis is formulated via an H/spl infin/ static output control problem and is solved using an iterative linear matrix inequalities (ILMI) algorithm. A three area power system example with possible contract scenarios and wide range of load changes is given to illustrate the proposed approach. The resulting controllers are shown to minimize the effect of disturbances and maintain the robust performance

A scenario on load-frequency controller design in a deregulated power system

An approach based on mu-synthesis and analysis theory is proposed for the design of load frequency controller in response to the new technical control demand for power system in a deregulated environment. In this approach the power system is considered as a collection of separate control areas and each control area can buy electric power from some generation companies to supply the area-load. The proposed technical scenario is illustrated with application to the design of load-frequency controller for a typical control area. The resulting controller is shown to minimize the effect of disturbances and achieve acceptable frequency regulation in presence of uncertainties and load variation

Robust Decentralized LFC Design In a Deregulated Environment

In this paper, a decentralized robust approach is proposed for load-frequency control (LFC) design in a deregulated environment using bilateral market scheme. First, the effect of bilateral contracts as a set of new input signals is taken into account in the control area dynamical model, and then the LFC problem will be formulated as a multi-objective problem to cover robust performance,practical constraint on control action and minimize the effects of load disturbance under wide range of demand changes. A mixed H2/Hinf is used to solve the problem and design the desired robust controllers. A three control areas power system example with possible contract scenarios and load changes is given to illustrate the proposed approach. The resulting controllers are shown to minimize the effect of disturbances and maintain the robust performance

PI-based multi-objective load-frequency control in a restructured power system

This paper addresses a new decentralized robust LFC design in a deregulated power system under bilateral-based policy scheme. The LFC problem is formulated to a PI based multi-objective control problem via a mixed H2/Hinf control technique. The robust PI control problem is reduced to a static output feedback control synthesis, and it is solved using a developed iterative linear matrix inequalities algorithm to get a robust performance index close to specified optimal one. The proposed method is applied to a 3-control area power system with possible contract scenarios and a wide range of load changes. The results are compared with H2/Hinf dynamic control design

DC-DC Quasi-Resonant Converters: Linear Robust Control

In this paper, a general robust control synthesis framework is proposed for DC-DC quasi-resonant converters (QRCs) in order to achieve both stability and desired performance, such as reduced sensitivity to load variations, desired disturbance rejection, reduced output impedance and attenuated transfer from input to output. The mu-analysis is used to design and verify the robustness of the resulted controller. The proposed control strategy is applied to a typical zero-current switching QRC and nonlinear simulation is performed using nonlinear model of converter circuit. The simulation results demonstrate the good reference voltage tracking, line disturbance rejection and show7 that the designed procedure guarantees the robust stability and robust performance for a wide range of load variation