Nonlinear control device for a dc/dc converter used for conveying hvdc current

A multi-level DC/DC converter comprising n conversion stages, n being greater than or equal to 2, said converter being adapted to transfer power in bidirectional manner between at least one individual DC voltage source (10;

• 10′) and a DC voltage network source (60), the voltage (Vout-total) of said network source being greater that that of each of said individual sources, each of the n conversion stages comprising:
• a converter module (30′) adapted to transfer power in bidirectional manner between one of the individual DC voltage sources and said DC voltage network source, said converter module (30′) comprising a transformer (21) having a primary winding (21a) and a secondary winding (21b) and leakage inductance (21c), the transformation ratio (m) of said transformer being greater than 1, said converter module (30′) further comprising a first converter (20a) and a second converter (20b), each of said converters containing a plurality of gate-controlled bidirectional switches (J1,J2,J3,J4,J5,J6,J7,J8) in a single-phase bridge configuration for converting a DC voltage into an AC voltage, said first converter (20a) being connected to the terminals of said primary winding (21a), said second converter (20b) being connected to the terminals of said secondary winding (21b), said primary winding (21a) having at its terminals a first AC voltage (V′in) and the secondary winding having at its terminals a second AC voltage (V′out), said first converter (20a) having at its terminals a first DC voltage given by the individual source to the terminals of which it is connected and the second converter (20b) having at its terminals a second DC voltage given by said network source;
• the second converters (20b) of each of the n conversion stages being in placed parallel, the sum (Vout) of the n voltages being output by the said second converters (20b) being equal to the voltage (Vout-total) of the network source, characterized in that each of the n conversion stages comprises in addition:
• an independent control module that is identical in each of the n conversion stages, adapted to control the converter module (30′) of said conversion stage, said control module being connected to the gates of the switches (J1,J2,J3,J4,J5,J6,J7,J8) of said converter module (30′) in order to control their switching states during a switching period T, said control module being configured to compare the value of the current (i1) in said first converter (20a) with a reference current (im1-ref) and to adjust the phase offset (d) between the AC voltages at the primary winding (21a) and at the secondary winding (21b) of said transformer (21) as obtained by switching said switches (J1,J2,J3,J4,J5,J6,J7,J8), the adjustment being a function of the result of the comparison, in such a manner as to adjust the power conveyed by said converter module (30′).