Modeling And Control Of Waste Heat Utilizing Processes

Due to energy shortage and environmental constraints, the interest in low-quality heat recovery has grown dramatically in the past decades. Many scholars have done a lot of research. Recycling of waste heat with organic Rankine cycle (ORC) has many advantages, such as recycling energy and protecting environment.Waste heat recycling process is a complex process which is nonlinear and multi-coupling. In this paper, based on the previous work, the dynamic model of key components of ORC system which are evaporator, expander, condenser, pump were established. Then the control-oriented model of ORC system can be obtained, which can describe the dynamic characteristic of waste heat recycling processes and provide theoretical basis for designing control system.This paper presents a method of designing self-tuning PID controller based on genetic algorithm for an evaporator in ORC system. The purpose of the control system is to control the outlet temperature of evaporator through adjusting the velocity of the exhausts. Genetic algorithm can optimize the parameters of PID controller through reproduction, crossover and mutation. Compared with Ziegler-Nichols PID controller, the self-tuning PID controller can achieve better control performance.ORC system is a complex multi-input multi-output system and the general linear quadratic regulator can’t eliminate the steady-state error. In order to achieve both transient performance and steady-state energy savings, a multi-framework for the waste heat recovery system is proposed by incorporating linear quadratic regulation (LQR) strategy with PI controller. Simulations demonstrate that the combined strategy can obtain satisfactory performance.