Linear Matrix Inequality Approach for Robust State Feedback Control of Electric Spring: A Device for the Real Time Demand Side Management

Abstract

Ever-Increasing environmental concern has raised the penetration of renewable energy sources in the power grid, which brings instability to the grid due to its intermittent nature. Electric Spring (ES) was proposed as the decentralized mechanism to bring voltage regulation and stability to the grid, when being installed at the customer’s end. This work focuses on the control aspect of the ES, being used for providing voltage regulation to the critical load by manipulating the voltage across the non-critical load, amidst fluctuating voltage inflicted by renewables, through injecting voltage with appropriate magnitude and phase. State-Feedback control of ES has been designed using the Linear Quadratic Regulator, being optimized using the numerical convex optimization called Linear Matrix Inequalities, to furnish robustness to the control with optimal control effort. The Cyclic Design approach has been used to transform MIMO system into SISO system, to provide simplicity to the controller design without sacrificing its robustness and efficacy. Integrator has been introduced there in, to bring the steady-state error to zero. The superiority of the proposed control has been established through comparison of results derived through this controller with that of a PI controller, which is widely used for executing the control of ES.