A method of setting a reference DC-link voltage of a wind-turbine converter system, wherein at least one generator-side inverter and at least one grid-side inverter of the converter system are electrically coupled by the DC-link, the method comprising: receiving at least one DC voltage demand from at least one generator-side inverter, receiving at least one DC voltage demand from at least one grid-side inverter, determining a generator-side DC voltage demand value on the basis of the at least one DC voltage demand received from the at least one generator-side inverter, determining a grid-side DC voltage demand value on the basis of the at least one DC voltage demand received from the at least one grid-side inverter, setting the reference DC-link voltage with regard to the generator-side DC voltage demand value and the grid-side DC voltage demand value, wherein setting the reference DC-link voltage comprises: selecting the highest DC voltage demand value out of the generator-side DC voltage demand value and the grid-side DC voltage demand value determining the reference DC-link voltage on the basis of said highest DC voltage demand value, characterized in that the converter system comprises at least two converter strings, wherein the generator-side inverters of the first and second converter string (15, 16) are connected in series and the grid-side inverters of the first and second converter string are connected in series, wherein the series connection of the grid-side inverters of the first and second converter string and the series connection of the generator-side inverters of the first and second converter string each form a neutral connection point and these neutral-connection points are connected to each other by a center connection line, and wherein the series connection of generator-side inverters and the series connection of grid side inverters is coupled to each other via a positive DC level conductor and a negative DC level conductor, wherein a generator-side DC voltage demand value of a first converter string is determined on the basis of at least one DC voltage demand of the generator-side inverters of the first converter string, a grid-side DC voltage demand value of the first converter string is determined on the basis of at least one DC voltage demand of the grid-side inverters of the first converter string, a DC voltage reference value of the first converter string is determined on the basis of the grid-side and generator-side DC voltage demand (D41, D42) values of the first converter string, a generator-side DC voltage demand value of a second converter string is determined on the basis of at least one DC voltage demand of the generator-side inverters of the second converter string, a grid-side DC voltage demand value of the second converter string is determined on the basis of at least one DC voltage demand of the grid-side inverters of the second converter string, a DC voltage reference value of the second converter string is determined on the basis of the grid-side and generator-side DC voltage demand values (D51, D52) of the second converter string, and wherein the reference DC-link voltage (30, 30') is set using the determined DC voltage reference values of the first and second converter string (41, 51). receiving at least one DC voltage demand from at least one generator-side inverter, receiving at least one DC voltage demand from at least one grid-side inverter, determining a generator-side DC voltage demand value on the basis of the at least one DC voltage demand received from the at least one generator-side inverter, determining a grid-side DC voltage demand value on the basis of the at least one DC voltage demand received from the at least one grid-side inverter, setting the reference DC-link voltage with regard to the generator-side DC voltage demand value and the grid-side DC voltage demand value, wherein setting the reference DC-link voltage comprises: selecting the highest DC voltage demand value out of the generator-side DC voltage demand value and the grid-side DC voltage demand value determining the reference DC-link voltage on the basis of said highest DC voltage demand value, characterized in that the converter system comprises at least two converter strings, selecting the highest DC voltage demand value out of the generator-side DC voltage demand value and the grid-side DC voltage demand value determining the reference DC-link voltage on the basis of said highest DC voltage demand value, characterized in that the converter system comprises at least two converter strings,