Abstract

The running project of gas transport optimization is described in following structure:

  • Long-term optimization for evaluation, comparison and optimization of transport strategy,. network development and use.

  • Short-term steady-state optimization which checks the feasibility of transport requirements and elaborates the optimum switching of the pipeline system and the optimum configuration of machines within compressor stations.

  • Short-term transient optimization which generates the operation for an ahead time period of several days.

In the first section, the concept of "price variable" is defined and demonstrated in use. The sections dedicated to item (ii) and (iii) outline the original theoretical means which make both the tasks of steady-state and transient optimum control feasible. Actual state of development is given together with the perspectives of further progress. All three tools are demonstrated and documented by examples of practical use.

1 Introduction

Elaboration of the control system of any technology consists of two steps:

  1. Analysis of the dynamics of the technology to be controlled. This step is usually called system identification. Its result is the simulation model - a tool which behaves in both steady state and dynamic situations in the same manner as the real system does, with one only exception: in the model, all processes are running quicker than in the reality. The quicker, the better the model.

  2. Synthesis of the control system. In this step a system is elaborated which changes some inputs of the technology (or proposes the changes) in the manner to attain the desired state and behavior.

In the most advanced case, the control system aspires to maintain the optimum behavior of the technology. The synthesis is based on identification results. Our former research activity in pipeline network identification resulted in a system for simulation of dynamics, applicable-for a network of any configuration and any extent [3], [11], [12], [9], [10]. The simulation system features detailed modelling of any technological equipment, mainly the compressor stations [8] and blending stations, modelling of heat dynamics [19], [20], quality tracking IS], state reconstruction [3], identification of systematic errors of measurements [3], [l], leak detection [l], etc.. This system is actually used both off-line and on-line by large European gas transporters for design [17], planning[7], control [13], etc. purposes, and its distribution is in further progress. Thus, the identification being completed, the task that faces us is the synthesis of the control system which is the subject of this paper. The project of control of gas transport and distribution is very wide and structured: the requirements vary from short term control, the subject of which is the daily operation of the system, to the very long time (year(s)) h orizons of strategic economic planning. The first ones are determined more by the technical feasibility and objectives, whereas the second ones reflect more the aspects of commercial policy. The control of short term processes is determined by the dynamics of the system, whereas the long term strategy and decision making depend on steady states only.

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