A highly efficient, easy-to-implement, three-phase uninterruptible power supply (UPS) with 20 kW and 400 V for top-tier power protection and low total operating costs at the network edge, in small and medium-sized data centers, as well as for critical infrastructure in commercial and industrial applications. This UPS is designed for up to 4 intelligent high-capacity battery strings but is delivered without batteries. This allows for easy adaptation with the appropriate battery modules for various autonomy times. Includes start-up service 5 x 8.