Direct connection emonTx V3 3-phase to RaspberryPi

Yes, use the emonhub directserial-serialtx3e interfacer. Just add the emonhub config in the [interfacers] section:

[[SerialTx3e]]
     Type = EmonHubTx3eInterfacer
      [[[init_settings]]]
           com_port= /dev/ttyUSB0
           com_baud = 115200
      [[[runtimesettings]]]
           pubchannels = ToEmonCMS,

This should decode the serial output from the latest emonTx-three phase (V0.11.0)