Keiko Shimizu

Practical Model and Detection Algorithm for Valve Stiction

Abstract Stiction is the most common problem in pneumatic control valves, which are widely used in the process industry. Stiction causes fluctuation of process variables, which lowers productivity. Therefore, developing a method to detect stiction and distinguish it from other causes is crucial to help operators take an appropriate action for improving control performance. The present work proposes a valve stiction model and new stiction detection algorithms. Using only two parameters, the proposed model can describe the stiction phenomenon with sufficient accuracy. The usefulness of the proposed detection methods are demonstrated by comparing them with a conventional method. The proposed methods are shown to successfully detect valve stiction, distinguish it from bad tuning or disturbances, and quantify the degree of stiction, by using simulation data sets and real operation data sets of several chemical processes

Multivariable control for a combined cycle power plant

Abstract Several types of multivariable controllers, such as H ∞ , Linear Quadratic Regulator (LQR) and Generalized Predictive Controller (GPC), have been developed. Experimental results have been obtained. The controller structures are tested for practical application on a commercial plant. Each controller shows not only a good transient response along with decoupling performance, but also robust properties over a wide operating range.

Generalized Predictive Control for a NO x Decomposition Process of a Combined Cycle Power Plant

Abstract A control system for a nitrogen oxide (NOx) decomposition process in a combined cycle power plant is developed using a Generalized Predictive Control(GPC) method and a Linear Quadratic Regulator (LQR) method. NOx in a gas turbine (GT) exhaust gas flow is decomposed by anmonia (NH3) at catalysts. A NH3 flow rate is adjusted to keep the NOx exhaust flow rate at a setpoint. The control system has a cascade scheme that includes NOx flow control designed by a GPC method and NH3 control designed by an LQR method. Experimental results on a commercial power plant shows not only a control performance but also a practicability

Override configuration of generalized predictive control for a multi-purpose control problem

Abstract Generalized Predictive Control (GPC) proposed by Clarke et al. is widely used in process control fields. In this paper, an override configuration is presented to a multipurpose control where some plant variables are constrained by upper and/or lower limits. Each compensator that constitutes the override controller is designed by GPC. The controller with override loops can avoid iterative calculations such as QP for a constrained optimization probrem. Nitrogen oxide decomposition process in a thermal power plant is chosen as a numerical example. The override arrangement GPC shows successful performance in simulation studies.

Multivariable Control for a Combined Cycle Power Plant

Abstract Several types of multivariable controllers, such as H ∞ , Linear Quadratic Regulator (LQR) and Generalized Predictive Controller (GPC), have been developed. Experimental results have been obtained. The controller structures are tested for practical application on a commercial plant. Each controller shows not only a good transient response along with decoupling performance, but also robust properties over a wide operating range.

T-DOF GENERALIZED PREDICTIVE CONTROL AND AN APPLICATION FOR A LARGE DEAD TIME PROCESS OF A THERMAL POWER PLANT

Abstract In this paper we describe a two-degree of freedom (T-DOF) configuration of a generalized predictive control (GPC) and an application for an NOx decomposition process of a combined cycle power plant. T-DOF GPC that is designed with feedforward signals, measurable disturbance signals and a reference signal is able to prevent an undesirable action that is caused by the feedforward control. We also describe that the present T-DOF GPC is a similar to the controller with the minimal order observer. We show experimental results accomplished on a commercial power plant.

Override Configuration of Generalized Predictive Control for a Multi-Purpose Control Problem

Abstract Generalized Predictive Control (GPC) proposed by Clarke et al. is widely used in process control fields. In this paper, an override configuration is presented to a multipurpose control where some plant variables are constrained by upper and/or lower limits. Each compensator that constitutes the override controller is designed by GPC. The controller with override loops can avoid iterative calculations such as QP for a constrained optimization probrem. Nitrogen oxide decomposition process in a thermal power plant is chosen as a numerical example. The override arrangement GPC shows successful performance in simulation studies.