MINES ParisTech CAS - Centre automatique et systèmes


7 janvier 2008, Salle R05, au Centre Automatique et Systèmes, Fontainebleau
10h00 : Dr. Matthias BITZER, Robert Bosch GmbH, Allemagne.
The use of storage tanks for domestic hot water in contemporary heating systems has proven great potential to save energy and increase comfort and availability. Thereby, the state of the art system for domestic hot water storage is the so-called stratified storage tank. The entire considered heating system consists of a burner, a heat exchanger, as well as the mentioned storage tank which are interconnected by respective tubings at their boundary outlets.
The dynamics of the plant is characterized by discrete-time events due to tapping or loading scenarios as well as continuous-time spatial temperature profiles which occur in the storage tank, the heat exchanger, and the burner. Each plant component is therefore represented by a respective distributed parameter model. Thus, the entire plant model consists of a finite state automaton interacting with a continuous-time model of six underlying coupled distributed quasi-linear partial differential equations. Consequently, the entire plant can be interpreted as a hybrid distributed parameter system.
In this talk, a model-based process control concept for the energy-efficient loading of the storage tank by means of the components heat exchanger and burner is discussed. The manipulated variables are the gas temperature within the burner as well as the secondary-side flow velocity of the heat exchanger. The controlled variable is the output temperature of the heat exchanger which is at the same time the input temperature of the storage tank. One output of the storage tank is connected to the heat exchanger and consequently corresponds to a disturbance. Reconstructing the spatial temperature profile in the storage tank by means of a distributed parameter observer allows the derivation of optimized loading trajectories for the process control.
The proposed control concept is set-up in a modularized manner for the two components burner and heat exchanger. Thereby, the control scheme for the burner is based on an I/O-linearization derived using a reduced-order Galerkin model. The respective control approach for the heat exchanger includes an inversion of a linear distributed parameter model as feedforward control and utilizes an underlying PI-control as feedback. The inversion of the model is based on a numerical inverse Laplace transform of the inverted transcendent transfer function for the desired non-flat output of the heat exchanger. Thereby, the feedforward furthermore compensates for disturbances occurring as a consequence of the actual loading state of the tank, i.e. its spatial temperature distribution.
The work has been done in cooperation with Tobias Kreuzinger (Robert Bosch GmbH) and Prof. Wolfgang Marquardt (RWTH Aachen).