An Intelligent Coordinated Control Scheme for Full-Mode Smooth Operation of Parallel Energy Storage System

In this paper, an intelligent coordinated control scheme is proposed for the full-mode smooth operation of the parallel energy storage system (ESS). The proposed scheme includes a power intelligent control loop and a voltage and current coordinated control loop. The intelligent power control loop can automatically adjust the ESS to grid-following control or grid-forming control to obtain optimal operation according to the grid-connected or islanded mode. The voltage and current coordinated control loop can automatically coordinate the gain of the controller during the mode transition between grid-connected and islanded modes, so as to achieve smooth mode transition. Especially for the unintentional islanding, the proposed intelligent limiter can adaptively adjust the limiting value to obtain the optimal voltage reference, so that ESS can quickly respond to the optimal voltage control. The proposed scheme can significantly reduce the voltage and power impact caused by conventional unintentional islanding, thus ensuring the smooth off-grid of the system. The mechanism analysis and parameter design of the proposed scheme are carried out. Finally, the experimental results show that the proposed scheme can achieve the full-mode smooth operation of grid-connection and islanding and their mutual transition.