Abstract: A dynamic stability analysis and control method for a voltage sourced converter based high voltage direct current (VSC-HVDC) transmission system. The method includes the following steps: unlocking a converter station of the VSC-HVDC transmission system to make the VSC-HVDC transmission system run in a non-island control mode; extracting corresponding parameters of the VSC-HVDC transmission system, wherein the parameters include an effective voltage value Ut0 of an AC system, an outgoing reactive power Qvsc0 of the VSC-HVDC transmission system, a gain kp of a phase-locked loop (PLL), and a proportional integral time constant ki of the PLL; calculating a short-circuit ratio (SCR), an unit value of Ut0 and an unit value of Qvsc0; calculating a key stable component; checking the sign of the key stable component to determine the stability of the VSC-HVDC transmission system.

Abstract: A T-type DC circuit breaker includes a main branch, a first commutation switch, a second commutation switch, and a bypass branch. The first commutation switch and the second commutation switch are arranged at both ends of the main branch, respectively. The bypass branch is connected in parallel with the main branch. The main branch includes at least one half-controlled power electronic component. The bypass branch includes a bypass capacitor and a bypass diode connected in series. Each of the first commutation switch and the second commutation switch includes at least one fully-controlled power electronic component. The first commutation switch is connected in parallel with a first surge arrester, and the second commutation switch is connected in parallel with a second surge arrester. The grounded branch is arranged between the main branch and the second commutation switch and is grounded or connected to the negative terminal of the load.

Abstract: A T-type DC circuit breaker includes a main branch, a first commutation switch, a second commutation switch, and a bypass branch. The first commutation switch and the second commutation switch are arranged at both ends of the main branch, respectively. The bypass branch is connected in parallel with the main branch. The main branch includes at least one half-controlled power electronic component. The bypass branch includes a bypass capacitor and a bypass diode connected in series. Each of the first commutation switch and the second commutation switch includes at least one fully-controlled power electronic component. The first commutation switch is connected in parallel with a first surge arrester, and the second commutation switch is connected in parallel with a second surge arrester. The grounded branch is arranged between the main branch and the second commutation switch and is grounded or connected to the negative terminal of the load.

Abstract: A dynamic stability analysis and control method for a voltage sourced converter based high voltage direct current (VSC-HVDC) transmission system. The method includes the following steps: unlocking a converter station of the VSC-HVDC transmission system to make the VSC-HVDC transmission system run in a non-island control mode; extracting corresponding parameters of the VSC-HVDC transmission system, wherein the parameters include an effective voltage value Ut0 of an AC system, an outgoing reactive power Qvsc0 of the VSC-HVDC transmission system, a gain kp of a phase-locked loop (PLL), and a proportional integral time constant ki of the PLL; calculating a short-circuit ratio (SCR), an unit value of Ut0 and an unit value of Qvsc0; calculating a key stable component; checking the sign of the key stable component to determine the stability of the VSC-HVDC transmission system.