Higher Order Sliding Mode Based Parameter Estimation and Control of a Pressurized Water Reactor.

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Title

Higher Order Sliding Mode Based Parameter Estimation and Control of a Pressurized Water Reactor.

Abstract

In this thesis a novel model validation, parameter estimation and controller design for a 998 MW pressurized water reactor is presented. First of all, the non-linear model of the pressurized water reactor is validated with experimental data. The change in reactivity which is calculated from control rod position, is given to the nonlinear model. Two measurable outputs of the reactor are compared with the output of the model. The parameters of the model are calculated from design documents and available literature. After that, important parameters of a pressurized water reactor like precursor density, change in reactivity and average fuel temperature are estimated. The precursors are important parameters which make the control of nuclear reactor possible. There is no physical sensor to measure precursor density directly. A second order sliding mode observer is designed to estimate precursor density. The change in reactivity is an input to the reactor. If reactivity is positive then the reactor power increases and if it is negative the reactor power decreases. In case of zero reactivity the reactor power is in steady state. The change in reactivity cannot be measured directly so an observer is required to estimate it. Average fuel temperature of reactor is also an important parameter directly related to safety of reactor. In the existing technology there is no device to measure fuel temperature. Therefore, its estimation is also required. A uniform robust exact differentiator observer is designed to estimate the change in reactivity and average fuel temperature. After parameter estimation robust controller is designed for controlling thermal power and reactor core outlet temperature. The pressurized water reactor controller takes the turbine power as reference. For controlling the output power of the reactor a robust controller is required which can cope with non-linearities and parameter variations due to fuel burn up and change in power level. Therefore, a second order sliding mode controller is designed in two different ways. In the first method super twisting algorithm is used which needs only the measurement of reactor power. While in the second method real twisting algorithm is used which needs the measurement of power and coolant temperature. Transient and steady state response of a pressurized water reactor in the presence of disturbance and model uncertainties is evaluated.

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