Voltage source converter and operation method thereof

The voltage source converter comprises at least two half-bridges (15), each having two current valves (21, 22) connected in series and configured to be connected to opposite poles (6, 7) of a DC source/load. Each half-bridge has a gate driving unit (32) configured to control respective on and off of the semiconductor devices of the current valves. Each gate drive unit (32) comprises an arrangement (36) configured to perform a voltage measurement to provide a value of a DC voltage between the opposite poles (6, 7). Each of the arrangements comprises a voltage divider (37) connected across the two current valves of the respective half-bridge to measure the overall DC voltage between the opposite poles, and each voltage divider has an output connected to a processing section (38) that delivers a digital signal representative of the value of the DC voltage between the poles. At least two gate drive units (32) are configured to send the digital signals to a calculation unit (54) configured to perform quality estim