Patent ID: 8848401

Claim:
A power electronic converter, for use in high voltage direct current power transmission and reactive power compensation, comprising at least one converter limb including first and second DC terminals for connection in use to a DC network and an AC terminal for connection in use to an AC network, the or each converter limb defining first and second limb portions connected in series between the AC terminal and a respective one of the first and second DC terminals, each limb portion including a chain-link converter connected in series with at least one primary switching element, each chain-link converter including a plurality of modules connected in series, each module including at least one secondary switching element connected to at least one energy storage device, the or each primary switching element in each limb portion of a respective converter limb selectively defining a circulation path carrying a DC circulation current to regulate the energy level of at least one energy storage device in a respective chain-link converter, wherein the or each primary switching element is controlled to simultaneously switch both limb portions into circuit to define the circulation paths, the or each primary switching element of each limb portion selectively defining the circulation path for a predetermined overlap period to control the duration for which the DC circulation current flows.