Time-varying time delay tracking in district heating systems

Hongping Zhao and Jan Holst

Department of Mathematical Statistics,
Lund Institute of Technology,
Lund University,
1998

ISSN 0281-1944
ISRN LUTFD2/TFMS--3148--SE


Abstract:
Accurate estimation of time-varying time delay is a crucial precondition for an efficient and effective control system. In the paper existing models and methods for tracking time-varying time delay in district heating (DH) systems are reviewed. It seems that due to wide and very quick variation of the time delay in DH systems, existing methods mainly based on time series theory appear to demand heavy computation, (estimates) to be of time delayed, and of weak robust. Based on physical principle, a deterministic model for time-varying time delay in DH systems is given, which shows that the time delay is an integration function of mass flow rates. Based on the model, a new time delay estimation algorithm is then suggested. Case studies show that the suggested method is superior compared with other existing methods.
Key words:
district heating, time-varying time delay, tracking