Development of an Efficient Load Frequency Controller for Pico Hydropower Generation System in Sewage Treatment Plant

Abstract

Over the past few decades, with the rapid industrial development and population increase, electricity has become a necessity, and thereby a tremendous rise in demand has been created. However, given the growing concerns about climate change and the depletion of fossil fuels, it is essential to utilise renewable sources of electricity generation. By harnessing electricity through moving water, the Pico Hydropower Generation System (PHPGS) is among the most attractive small-scale hydropower and cost-effective sustainable energy technologies available. Naturally, moving water can be found in rivers and man-made conduits where there is a continuous water flow. The sewage treatment facility has continuous water flow at the effluent pipe that can generate electricity by means of a small hydropower system. According to the literature, a micro hydro turbine system with a maximum power output of 38 kW was installed as a pilot trial in Hong Kong's Stonecutters Island STP, which uses sewage flow hydro energy for in-house use [15]. However, the power generated is based on the higher flow rate and outfall discharge head. Our research focus is on harvesting energy from lower flow rate and outfall discharge head by implementing the PHPGS in IWK's STP and using intelligent efficient controller to maintain voltage and frequency within limits as the incoming STP final effluent flowrate changes under dynamic conditions. Taking the other Pico Hydropower plant research work application as a comparison, the fixed control system from the previous research work does not offer the dynamic response monitoring for Pico Hydropower plants when the water incoming flow rates into the hydro turbine are varied. The purpose of this research was to develop an efficient PHPGS control system for a residential STP's continuous effluent discharge point with a low head and high flow fluctuations. This research proposes a combination of fuzzy and PID controllers for Self-Excitation Induction Generator (SEIG) voltage and frequency control and monitors the voltage quality through the efficient Load Frequency Controller (LFC) system under the final effluent incoming flow rate variation into the turbine. A Pico Hydropower plant has been modelled and simulated using the MATLAB/Simulink software. The operational limitation of this PHPGS model is determined within ± 20% from the STP average flow rate of 0.194 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /s. Through the disturbance which given at 4 (flow rate increased by 20 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">%</sup> ), the performance comparison between coordinated PID-Fuzzy, Fuzzy and conventional PID controllers in terms of dynamic response has been carried out. The results obtained showed that a coordinated PID-Fuzzy controller is more effective as compared to a Fuzzy or a conventional PID controller in terms of overshoots, rise time, settling time & steady state error with respect to increment of the final effluent incoming flow rate into the turbine. Overall, the outcome of modelling shows that the voltage and frequency remain efficiently within acceptable limits at 400 V and 50 Hz respectively as the incoming STP final effluent flow rate increased by 20% from the STP average flow rate of 0.194 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> /s.