Improving boiler performance during partial load rejections using a mixed fuzzy logic and LQG/LTR approach

Partial or full load rejections occur due to loss of one or more transmission lines or similar faults. Withstanding power station load rejections depends almost exclusively on the boiler control. This paper presents a fuzzy supervisory scheme to improve the performance of the boiler drum water level during such disturbances. This scheme consists of a robust local controller designed using the linear quadratic Gaussian with loop transfer recovery (LQG/LTR). The level set-point to the controller is modified whenever necessary by a fuzzy logic based supervisor.