control and protection system for converters in high-voltage dc transmission

摘要

A control and protection system for an AC-DC conversion system for exchanging an electric power between two AC power systems. The AC-DC conversion system is composed of two power converters and two circuit breakers connected to the two AC power systems. Each of the power converters is composed of a plurality of switching devices controlled by a gate signal and converts AC power into DC power or DC power into AC power. The control and protection system is composed of two control and protection units. Each of the control and protection units includes a protection unit for detecting a fault of the power converter to generate a first protection order signal when the fault is detected, and a phase control unit for continuously generating firing pulses to the switching devices of the power converter. Each of the control and protection unit further includes a protection sequence unit connected to the protection unit for receiving the first protection order signal, for holding the first protection order signal, for generating an opening instruction to the circuit breaker, and for generating a second protection order signal for stopping the power converter at another side to the control and protection unit at the another side, while the firing pulses are being supplied to the switching devices of the power converter.