First Experimental Results of a Grid Connected Vertical Axis Marine Current Turbine using a Multilevel Power Converter

An experimental marine current power station has been deployed in Söoderfors, Sweden. It comprises a vertical axis turbine directly connected to a permanent magnet synchronous generator rated at 7.5 kW. The generator is controlled by a Back-To-Back 2L-3L Cascaded H-Bridge full scale bi-directional Power Converter located on shore. This paper presents the first test results of the power converter, including grid connection. The startup of the turbine, power extraction and initial active power injection to the grid, at 50 % of rated power, operated as predicted by laboratory experiments and simulations. After 40 seconds of grid connection the safety system disconnect the grid converter due to high currents injected to the grid. The problem is mostly likely associated with the current controller in the dq0 frame. Further tuning of the PI regulators and the potential addition of an anti-windup could mitigate the control issue