Chemical reactors, heat exchangers, level-loops, and distillation columns are commonly encountered in the chemical process industry, and these are having a significant role in the functioning of any chemical process. For the smooth and efficient functioning of any such process, a robust control law design is an important work to be considered. In this paper, a modified 2DOF robust PID control law has been developed to ensure satisfactory performance in both the step and ramp type references and disturbances. Controller parameters are derived with Maximum sensitivity, Gain, and Phase margin specifications. Case studies with different chemical processes like CSTR, distillation column, heat exchangers, and boiler drum level-loop are included for both the nominal and perturbed cases. Lastly, a performance comparison of ISE (Integral of square error), ITAE (Integral time absolute error), IAE (Integral absolute error), and Total variation (TV) of the control signal is also included.

A dual-degree of freedom (dual-DOF) propor-tional-integral proportional-derivative (PI-PD) controller is developed for integrating-type chemical processes with delay. The interior-loop PD controller is designed based on user-defined gain and phase margin. For designing the external-loop PI controller, the moment-matching method is augmented with maximum sensitivity specifications. The suggested design is suitable for chemical processes like continuously stirred tank reactors, boiler steam drums, heat exchangers and distillation columns. Using benchmark models of the aforementioned processes, the closed-loop system outputs and control signals are compared to vindicate the primacy of the suggested dual-DOF PI-PD controller. To study the performance-robustness trade-off of this design, rigorous perturbation analysis is also carried out. The performance improvement achieved by the suggested dual-DOF PI-PD controller is also quantitatively compared with contemporary works.

In many industrial processes, e.g. temperature and level control, chemical reactors can be classified as a variant of integrating plus time-delay system. Controlling these processes is a difficult task due to open-loop instability, which consists of time-delay and unbounded output for bounded input. 1DOF PID control always leads to a large overshoot in set-point tracking for IPTD processes. In a 2DOF PID structure, tuning the set-point weights and the controller parameters is important to achieve good tracking and disturbance rejection properties. But tuning the set-point weights and the parameters of the cascade-feedback controller together is a difficult task. Usually, predetermined values for set-points are chosen, and a controller design is followed. In the present work, an alternative simple approach to obtain controller parameters along with set-point weights is presented which are tuned to yield good tracking and load–disturbance rejection. Explicit controller parameters for different classes of integrating processes are obtained using gain-margin, phase-margin, and inverse plant model which can also be used for controller auto-tuning. To validate the effectiveness of the proposed controller, simulation comparisons with some recently developed methods are included. Moreover, the experimental validation of the proposed controller on a temperature control plant is also presented.

This paper presents a cyber-physical testbed, developed to investigate the complex interactions between emerging microgrid technologies such as grid-interactive power sources, control systems, and a wide variety of communication platforms and bandwidths. The cyber-physical testbed consists of three major components for testing and validation: real time models of a distribution feeder model with microgrid assets that are integrated into the National Renewable Energy Laboratory's (NREL) power hardware-in-the-loop (PHIL) platform; real-time capable network-simulator-in-the-loop (NSIL) models; and physical hardware including inverters and a simple system controller. Several load profiles and microgrid configurations were tested to examine the effect on system performance with increasing channel delays and router processing delays in the network simulator. Testing demonstrated that the controller's ability to maintain a target grid import power band was severely diminished with increasing network delays and laid the foundation for future testing of more complex cyber-physical systems.