Yes, a meter or a CT is needed for export control(In the on-grid inverter series,only single phase on-grid inverters are compatible with CT,three phase on-grid inverters are not compatible with CT) . Once a meter or a CT is connected, you should configure the inverter via LCD screen(App for non-screen version). Go to setting item 'Export control' to enable meter(or CT) and then confirm how much power to inject to the grid. If you want zero injection, you just need to set the value to 0.