This document describes functions and working principles, specifies requirements, interfaces, and test methods for controlled converters for DC electric traction power supply systems: " AC/DC converters Rectifiers Inverters Combinations " DC converters Purpose of the converters can be a power connection to other power networks or energy storages. Common characteristic of this equipment is the possibility to influence the power flow in the DC electric traction power supply system. The converters can be: " Line commutated " Self-commutated This document applies to fixed installations of following electric traction systems: " railway networks, " metropolitan transport networks including metros, tramways, trolleybuses and fully automated transport systems, magnetic levitated transport systems, electric road systems.