Virtual Synchronous Machine Control for 1.5kV Battery Units with Parallel Voltage-Controlled Inverter

This paper presents a novel implementation of a battery charging system operating at 1.5 kV DC, employing the Virtual Synchronous Machine (VSM) algorithm to control two bidirectional DC-AC converters operating in parallel. The VSM mimics a synchronous generator's inertia and damping effect, providing grid voltage-and-frequency support. A VSM can be easily operated in both generating and motoring mode. Hence, it provides a useful way to control the storage devices in large-scale battery system applications avoiding the need for a dedicated DC-DC converter. The proposed VSM implementation is described in detail, and its dynamic performances in grid-connected are demonstrated by simulations. Moreover, operation in islanding condition is also investigated. Due to the inherent grid-forming capability of this control strategy, the possibility of supplying power to the loads connected to the local grid, avoiding service discontinuity during grid faults and exploiting the energy previously stored in battery energy storage systems (BESSs), is of great interest in the development of the future smart grids. Experimental results are expected to confirm the feasibility of this approach for medium-voltage applications in renewable energy storage systems (RESSs).