CONVERTER

摘要

A voltage source converter includes a converter limb having limb portions separated by an AC terminal and extending between DC terminals, each limb portion including a primary switching element to switch the limb portion into and out of circuit. The converter further includes an auxiliary limb. The primary switching element of each limb portion is switchable to switch the auxiliary limb into and out of circuit with the corresponding limb portion. The converter further includes a control unit to, in one mode, inject a circulation current that flows in one direction in one of the limb portions and minimize a current flowing in the opposite direction in that limb portion. Each primary switching element switches the respective limb portion into or out of circuit following the minimization of the limb portion current by the circulation current.

主权项

1. A voltage source converter comprising:
a converter limb extending between first and second DC terminals and having first and second limb portions separated by an AC terminal, the first and second DC terminals being connectable to a DC electrical network and the AC terminal being connectable to an AC electrical network, each limb portion including a primary switching element, the primary switching element of each limb portion being switchable to switch the corresponding limb portion into and out of circuit between the corresponding DC terminal and the AC terminal to control the configuration of an AC voltage at the AC terminal; an auxiliary limb including an auxiliary converter, the auxiliary converter including at least one auxiliary switching element, the auxiliary limb being connected to the AC terminal, the primary switching element of each limb portion being switchable to switch the auxiliary limb into and out of circuit with the corresponding limb portion and thereby switch the auxiliary limb into and out of circuit with the corresponding DC terminal; and a control unit to selectively control the switching of the or each auxiliary switching element of the auxiliary converter to control the auxiliary limb as a current source in a primary operating mode to inject a circulation current that flows in one direction in one of the first and second limb portions to minimize a limb portion current flowing in the opposite direction in that limb portion, wherein the primary switching elements are configured to switch the one of the first and second limb portions out of circuit between the corresponding DC terminal and the AC terminal and switch the other of the first and second limb portions into circuit between the corresponding DC terminal and the AC terminal, following the minimization of the limb portion current by the circulation current, when a minimal or zero current flows through the corresponding primary switching element during the commutation of current from the one of the first and second limb portions to the other of the first and second limb portions.