Single-direction power-transmitted low-cost direct-current transmission system

The invention relates to a single-direction power-transmitted low-cost direct-current transmission system which has the characteristics of high reliability and low cost. The technical scheme is as follows: the single-direction power-transmitted low-cost direct-current transmission system has the structure that a diode rectifier, a direct-current transmission line containing a positive wire and a negative wire, and a modular multilevel current converter are orderly connected in series between the transmitting end system and the receiving end system; the diode rectifier comprises a rectiformer and a diode rectifier bridge; the primary side of the rectiformer is connected with the transmitting end system which provides active-power three-phase alternating current, and the secondary side is connected with the alternating current input end of the diode rectifier bridge; the positive pole of the diode rectifier bridge is connected with the positive pole of the direct-current transmission line, and the negative pole of the diode rectifier bridge is connected with the negative pole of the direct-current transmission line; and the modular multilevel current converter comprises a plurality of submodules (SM), a plurality of buffer reactors (3.2), and a phase reactor (3.3) or converter transformer.