About Us
Grad Studies
MACC Researchers
Zhiwen Chong Zhiwen Chong
Principal Research Engineer

Start date
September 2004



B.Eng. (Chemical Engineering) McGill University. Minor in Management.
M.A.Sc. (Chemical Engineering) McMaster University.
Ph.D. (Chemical Engineering) McMaster University.

Work Experience
Multicentric Technology SB, CSE Datacet SB, Projects with Institut des matériaux industriels (IMI) and Les Brasseurs du Nord (Boréale)

Research Title
Dynamic Optimization and Control under Partial Shutdown Conditions

Research Objectives
Our research focuses on the development of systematic strategies and formulations for the optimal operation of plants under partial shutdown conditions. A partial shutdown is a type of circumscribed plant unit shutdown that permits the rest of the plant to continue operating to some degree. The goal of a partial shutdown strategy is to be able to manipulate the available degrees-of-freedom in a plant---during and after a shutdown---such that production is restored in an cost optimal fashion while meeting all safety and operational constraints. This can be accomplished through adjustments of production rates, recycles and buffer levels.

In order to compute these adjustments, we solve a differential-algebraic-equation (DAE) based dynamic optimization problem containing a model of the plant. Within this broad framework, we take a novel multi-tiered dynamic optimization approach that allows us to prioritize multiple competing objectives and specify the trade-offs from one tier to the next. An economics-driven Model Predictive Control (MPC) control structure is used to implement the trajectories on the plant.

Model discontinuities germane to partial shutdown handling were handled using a series of specialized mixed-integer formulations. Estimation of states, parameters and biases was accomplished using a constrained form of an Unscented Kalman Filter (UKF). This is done in order to mitigate the effects of plant-model mismatch. The estimation algorithm is accommodated within a multi-tiered dynamic optimization framework.

A new computer modeling language, MLDO (A Modeling Language for Dynamic Optimization) was created to transcribe and solve the dynamic optimization problems.

MACC Publications

Other Publications
E. Navarro-Flores, Z. Chong, and S. Omanovic, "Characterization of Ni, NiMo, NiW and NiFe electroactive coatings as electrocatalysts for hydrogen evolution in an acidic medium", Journal of Molecular Catalysis A: Chemical, 226(2), p 179-197, 2005.

E. Navarro-Flores, Z. Chong and S. Omanovic, "Nickel / Conducting Polymer Electrocatalysts For Hydrogen Evolution in an Acidic Medium", 18th Canadian Symposium on Catalysis, Montreal, QC. May 16, 2004.

Z. Chong and C.L.E. Swartz, "Dynamic re-optimization and control under partial plant shutdown scenarios", presented at the American Institute of Chemical Engineers (AIChE) Annual Meeting, 2006, San Francisco, CA. Nov 12-17, 2006.

Z. Chong and C.L.E. Swartz, "A Modeling Language for Dynamic Optimization", presented at the 56th CSChE Canadian Chemical Engineering Conference, Sherbrooke, QC. Oct 15-18, 2006.

Z. Chong and C.L.E. Swartz, "Model-based Control of Multi-Unit Systems under Partial Shutdown Conditions", Proceedings of the American Control Conference (ACC) 2009, St. Louis, MO. June 10-12, 2009.

Z. Chong and C.L.E. Swartz, "Discontinuous Modeling Formulations for the Optimal Control of Partial Shutdowns", 18th International Federation of Automatic Control (IFAC) World Congress, Milan, Italy 2011

Z. Chong and C.L.E. Swartz, "Multi-Tiered Dynamic Optimization of Partial Shutdowns with Constrained UKF-based State and Parameter Estimation", presented at the American Institute of Chemical Engineers (AIChE) Annual Meeting, 2012, Pittsburgh, PA. Oct 28-Nov 2, 2012.

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