Optimising Plantwide Control
Overall Course Objectives
Typical chemical plants may contain hundreds of measurements and control loops. Most control theories (those you have seen in the introduction to process control) assume that a control structure is already given at the start, which reduces the problem to tuning and calculation of a control law. In practice, however, given a plant design with its process flow diagram, a control engineer faces the following problems: i) which variables should be controlled, ii) which variables should be measured, iii) which inputs should be manipulated, and iv) which links should be established between them? These are the questions that the plantwide control course addresses. To this end, a systematic methodology based on hierarchical decomposition of the control problem into layers is used for designing a plantwide control structure based on process understanding. The performance of the control structure is then evaluated and further refined using dynamic simulations of the process in question in an iterative manner.
The goal of the course is thus to learn i) to manage the complicated task of designing a control strategy for the entire plant; ii) to understand process dynamics using dynamic simulations; iii) to develop and implement a control strategy that meets control design objectives (stabilize the system, optimize the economics, environmental sustainability and satisfy the constraints); and vi) evaluation of alternative solutions. Ultimately all these efforts are to help develop and operate better, safer, and optimal processes for chemical and biochemical industries.
See course description in Danish
Learning Objectives
- Perform a systematic analysis of the operation of chemical and biochemical process plants
- Derive a control structure based upon the process analysis
- Calculate the optimal point of operation for the control system
- Derive simple linear models for control design from complex process systems
- Analyse observability and controlability of a dynamical system
- Design multivariable PID control structures
- Formulate and design model based multivariable controllers, incl. LQR, LQG and MPC
- Evaluate controller’s performance using simulation and dynamic process model
Course Content
The course base is the synthesis of the plant and its derived operational goals which illustrate that process design and operation are two sides of the same fundamental problem. Selection of actuators and measurements for a basic control structure at the single variable layer is introduced from a systematic model analysis. In a subsequent synthesis step a pairing of actuators and measurements is selected. How the operational goals may be achieved in practice through control is illustrated for selected examples. These examples will also demonstrate characteristic control structures.
Recommended prerequisites
28351/28150/28864, An introductory course in chemical process control similar to 28351 or 28150.
An introductory course into Matlab/Simulink software such as 28864.
Teaching Method
Lectures & simulation exercises and project work.
Faculty
Remarks
The project includes derivation of a plantwide control strategy using a systematic approach and its evaluation using dynamic simulations. The plant in question is a typical processing unit in the kemical industry. A project report is prepared critically discussing and evaluating the performance of the plant wide control strategy.