A configurable power module (10; 80; 90; 140), for use in a power transmission network, comprising: a first sub-module including a first pair of series-connected switching elements (20, 22) separated by a first connection terminal and connected in parallel with a first energy storage device; and a second sub-module including a second pair of series-connected switching elements (38, 40) separated by a second connection terminal and connected in parallel with a second energy storage device, a connection module operable to interconnect the first and second sub-modules (12, 14) in first and second connection modes, wherein the connection module includes a first limb which extends between a first side of each of the first and second energy storage devices (26, 44); a second limb which extends between a second side of each of the first and second energy storage devices (26, 44); and a first connection module portion which includes a first pair of bi-directional current flow control elements (60, 62), one bi-directional current flow control element lying within the first limb and the other bi-directional current flow control element lying within the second limb, each of the bi-directional current flow control elements (60, 62) selectively blocking current flow through the corresponding limb (48, 52) in the same first direction (D 1) and permitting current to flow through the corresponding limb (48, 52) in the same second direction (D 2) opposite the first direction (D 1), wherein the first connection module portion further includes a first unidirectional current flow control element interconnected between the first side of the first energy storage device and the second side of the second energy storage device, which permits current to flow therethrough in only one direction, the first unidirectional current flow control element interconnecting the first and second limbs (48, 52) to selectively establish a first series connection between the first and second energy storage devices (26, 44) and permit current to flow through the connection module in the first direction (D 1) when each of the first pair of bi-directional current flow control elements (60, 62) is blocking current flow in the first direction (D 1), the connection module in the first connection mode arranging the configurable power module (10; 80; 90; 140) in a full-bridge arrangement in which a parallel connection between the first and second energy storage devices (26, 44) is established which has bidirectional current flow characteristics, and the connection module in the second connection mode interconnecting the first and second energy storage devices (26, 44) to permit the first and second energy storage devices (26, 44) to combine and generate a blocking voltage to oppose the flow of current between the first and second connection terminals (24, 42). a first sub-module including a first pair of series-connected switching elements (20, 22) separated by a first connection terminal and connected in parallel with a first energy storage device; and a second sub-module including a second pair of series-connected switching elements (38, 40) separated by a second connection terminal and connected in parallel with a second energy storage device, a connection module operable to interconnect the first and second sub-modules (12, 14) in first and second connection modes, wherein the connection module includes a first limb which extends between a first side of each of the first and second energy storage devices (26, 44); a second limb which extends between a second side of each of the first and second energy storage devices (26, 44); and a first connection module portion which includes a first pair of bi-directional current flow control elements (60, 62), one bi-directional current flow control element lying within the first limb and the other bi-directional current flow control element lying within the second limb, each of the bi-directional current flow control elements (60, 62) selectively blocking current flow through the corresponding limb (48, 52) in the same first direction (D 1) and permitting current to flow through the corresponding limb (48, 52) in the same second direction (D 2) opposite the first direction (D 1), wherein the first connection module portion further includes a first unidirectional current flow control element interconnected between the first side of the first energy storage device and the second side of the second energy storage device, which permits current to flow therethrough in only one direction, the first unidirectional current flow control element interconnecting the first and second limbs (48, 52) to selectively establish a first series connection between the first and second energy storage devices (26, 44) and permit current to flow through the connection module in the first direction (D 1) when each of the first pair of bi-directional current flow control elements (60, 62) is blocking current flow in the first direction (D 1), the connection module in the first connection mode arranging the configurable power module (10; 80; 90; 140) in a full-bridge arrangement in which a parallel connection between the first and second energy storage devices (26, 44) is established which has bidirectional current flow characteristics, and the connection module in the second connection mode interconnecting the first and second energy storage devices (26, 44) to permit the first and second energy storage devices (26, 44) to combine and generate a blocking voltage to oppose the flow of current between the first and second connection terminals (24, 42).