NOVELTY - The converter has a leg (300) comprising a first string (302) comprising a set of controllable semiconductor switches (S1-S4, 330) and two connecting nodes (310, 312). The first string is operatively coupled across first and second buses (306, 308). A second string (304) is operatively coupled to the first string via the connecting nodes. The second string comprises a set of switching units (334). The first string comprises first and second branches (314, 316), where the second branch is operatively coupled to the first branch via a third connecting node (318).    USE - Modular multi-level power converter i.e. three phase multi-level power converter e.g. direct current (DC)-alternative current (AC) converter or AC-DC converter, for use in solar, wind and renewable power generation devices. Can also be used for sing and two phase multi-level power converters used in non-renewable power generation systems e.g. thermal power plants, and hydroelectric power plants.    ADVANTAGE - The converter can generate high power/voltage/current output by utilizing half number of switching units as thyristors, so that manufacturing cost of the converter can be reduced, manufacturing complexity of the converter can be reduced, and power losses can be reduced. The converter can avoid the need for additional capacitors in a DC link.    DETAILED DESCRIPTION - The set of controllable semiconductor switches is an insulated gate bipolar transistor, a metal oxide semiconductor field effect transistor, a FET, a gate turn-off thyristor, an insulated gate commutated thyristor, an injection enhanced gate transistor, a silicon carbide based switch, a gallium nitride based switch or a gallium arsenide based switch. The first bus comprises a positive direct current bus, and the second bus comprises a negative direct current bus. INDEPENDENT CLAIMS are also included for the following:    (1) a method for power conversion    (2) a system for power conversion.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a portion of a power converter.    Controllable semiconductor switches (S1-S4, 330, 334)    Leg (300)    Strings (302, 304)    Buses (306, 308)    Connecting nodes (310, 312, 318)    Branches (314, 316)