An Intelligent Fuzzy Control Approach for a Back-Pressure Autonomous Industrial Microgrid

Frequency and voltage are two important parameters for proper operation of industrial power plants. To maintain these indices in the standard levels in various operating conditions, efficient control strategies should be organized. Otherwise, severe fluctuations in the frequency or voltage may jeopardize the system stability which ends in operation collapse. Such occasions are more potent in back-pressure industrial microgrids within which the cogeneration of electricity and steam happens. An increase in generator back-pressure or a decrease in input steam due to drops in gas pressure results in steam fluctuations on the generator's shaft. This initiates frequency oscillations wherein if no any control action is exerted, the frequency instability is likely to happen. This paper investigates the performance of a double-layer fuzzy based load shedding methodology over the frequency and voltage fluctuations of a real autonomous industrial microgrid. Contemplating as a practical solution, the intelligent load shedding mechanism receives the steam pressure and frequency deviations as the input signals. It is found that the proposed two-layer mechanism reduces the amount of load shedding, though the voltage of the plant is deteriorated. Finally, a three-layer fuzzy logic controller is preliminary proposed for load shedding and terminal voltage correction. The third layer of the fuzzy controller operates as a supervisory control level to update the gain of automatic voltage regulator. This fuzzy layer receives the output of the second layer and voltage deviations of the industrial plant.