Power converter topologies applied in uninterruptible power supply (UPS) structures. Static and rotational UPS. Reliability of UPS structures. DC and AC UPS circuits. Rectifiers - battery chargers, classic and modern topologies. AC mains power supply impact. Stationary accumulator batteries, capacity calculation, maintenance, room design and ventilation. Calculation of DC circuits and protection design. Inverters: classic and modern power topologies, control and protection circuits. The parallel connected operation of two and more inverters. Inverter synchronization techniques in noisy environment. Conventional phase locked loops and sinusoidal locked loops. Inverter output voltage control. Typical inverter power topologies and power circuit component selection. Control of the inverter output impedance. Control of neutral conductor current. Power flow control in meshed UPS network. Proportional resonant current control. Concept of synchroinverters - behaving like synchronous machines. Static transfer switches: control and component selection. Active power filters: topologies, design and control. The basic characteristics of stand by diesel generating units and gas turbines. Earthing of loads connected to UPS network and noise suppression. Uninterruptible power supply of active and passive load networks. Uninterruptible power supply ofmedium voltage networks with drives. Coordinative control of the several weakly coupled inverters connected in the same network. Coordination of reactive power flow and voltage distribution with inverter capability curves.