Robust Resonant Controllers for Distributed Energy Resources in Microgrids

Motivated by the problem of different types and variations of load in micro-grids, this paper presents robust proportional-resonant controllers with a harmonics compensator based on the internal model principle. These controllers ensure robust tracking of sinusoidal reference signals in distributed energy resource systems subject to load variation with respect to sinusoidal disturbances. The distributed generation resource and the resonant controllers are described using the augmented state system approach, allowing the application of the state feedback technique. In order to minimize the tracking error and ensure robustness against perturbation, a set of linear matrix inequalities (LMIs) are addressed for the synthesizing of controller gains. Finally, results obtained in the simulation for resonant compensators with the distributed energy system are presented, in which the controller is applied to the CC-CA inverter.

Error Dynamics Design via a Repetitive Loop for UDE-Based Robust Control to Reject Periodic Disturbances

The uncertainty and disturbance estimator (UDE)-based robust control has a two-degree-of-freedom nature through the design of the error dynamics and the design of the UDE filters. In the conventional design to handle periodic disturbances or mixed sinusoidal disturbances, high-order UDE filters incorporated with the internal model principle (IMP) or time-delay filters (TDF) are adopted to achieve the asymptotic reference tracking and the asymptotic disturbance rejection. In this paper, a new error dynamics design combined with a repetitive loop is proposed for the UDE-based robust control to achieve the asymptotic rejection of both step disturbances and periodic disturbances. The disturbance rejection performance is investigated through the two-degree-of-freedom nature, and the practical implementation of the proposed design is illustrated to eliminate the infinite bandwidth of the repetitive loop. The proposed design is validated through the simulation studies of a battery charging system with comparison to different reported designs of the conventional UDE-based robust control.

Design of IMC Tuned PID Controller for First Order Process with No Delay

IMC tuned PID controller’s present excellent set point tracking but sluggish disturbance elimination, because of introduction of slow process pole introduced by the conventional filter. In many industrial applications setpoint is seldom changed thus elimination of disturbance is important. The paper presents an improved IMC filter cascaded with Controller PID tuned by internal model principle (IMC-PID) for effective elimination of disturbance and healthy operation of non-regular first order process such as processes with no delay. The suggested filter eliminates the slow dominant pole. The present study shows that the recommended IMC filter produces excellent elimination of disturbance irrespective of where the disturbance enters the process and provides acceptable robust performance to model disparity in provisions of maximum sensitivity in comparison with other methods cited in the literature. The advantages of the suggested technique is shown through the simulation study on process by designing the IMC tuned PID controllers to maintain identical robustness in provisions of maximum sensitivity. The integral error criterion is used to estimate the performance. The recommended filter produces excellent response irrespective of nature of the process.