Reactive power in variable-speed converter-fed drives connected to the three-phase supply network

In the paper energy transmission system which transmits the energy from lower voltage AC network to higher voltage AC network is presented. The system contains the DC link subsystem. It is proven that step up chopper used in DC link subsystem decreases the inverter reactive power from AC network. The AC/DC/AC subsystem is used with synchronous generator system and in rotor circuit of slip-ring induction motor for slip energy recovery. Characteristics of the system with step up chopper are compared with characteristics of classical AC/DC/AC system. In presented system value of energy is controlled by step up chopper with constant phase- controlled angle of inverter. In classical system it is done by change of phase control angle. Theoretical considerations are supported by the experimental results.