Local Controller for an Autonomous Grid-Supportive Battery Energy Storage System

This article presents the complete design of a local controller for a grid-supportive battery energy storage (BES) system. The controller's objectives are: 1) to execute commands issued from the secondary controller; 2) to provide grid support; 3) to prevent converter overcurrent during transient low-voltage incidents; and 4) to maintain the state of charge of the battery. The grid support is divided into static, i.e., the droop-based, and dynamic, i.e., the inertia-based, voltage supports. The proposed controller uses an optimally designed full-state feedback approach, which merges the voltage and current controllers. This makes the design more systematic, flexible, and with better tradeoff in speed and damping. The proposed BES is autonomous, meaning that it does not have to be colocated with a renewable resource. This autonomous feature allows the BES to connect to any critical node in a system, detect disturbances through local measurements, and provide support regardless of the origin of the disturbance. Mathematical derivations, computer simulations, and laboratory experimental results of the proposed controller are presented in this article.