Initial Studies on Fuzzy PI Control for a Non-utility Generation Facility under a Demand Contract

Abstract

This paper focuses on the minimization of energy costs for a factory with a non-utility generation facility, where exact load following is difficult. The factory purchases any shortfall in energy from utilities under a demand contract. In the demand contract, the amount of energy that can be purchased in a 30 minute period is limited. To reduce energy costs, we propose load follow-up PI control with bias and fuzzy PI control based on the Takagi-Sugeno fuzzy model. The fuzzy PI control method considers the elapsed time and purchasable energy during each 30 minute period. We also optimize the control parameters and the purchasable energy in the demand contract by Particle Swarm Optimization (PSO). The evaluation function in PSO is the increase in monthly costs considering the energy cost per unit for the generation facility, and the purchasing price and basic contract rate for the utilities. The function is estimated by simulation using the available data for the factory. The optimization of the function is carried out using actual load data. The validity of the proposed methods is evaluated by comparing the approximate cost increase with that under fixed energy output from the generation facility.