A generator control strategy for reducing the load shedding amount after the UHVDC commutation failure

In the power grid of "strong DC and weak AC", the commutation failure of the ultra-high voltage (UHV) line will result in angle swing between two regional power grids. Our analysis show that, unlike the scenario in the single machine infinite bus system, the speed of angle swing between two regional power grids after the fault is slow since power vacant is not very large (compared with the moment of inertia of the regional power grid). The first swing may last for several seconds. In this paper it is possible to improve the stability by changing generators output. We propose a new control strategy in this paper. The control strategy is as follows: when UHV commutation failure happens, signals are sent to generators in local power grid so that they can increase power output to compensate for the power vacant. At the same time, signals are also sent to generators in remote regional power grid to decrease their power output. This way, out of step can be avoided. Under typical simulation parameters configuration, a generator can increase/decrease mechanical power output by 6 % in 4s after the fault happens. The simulation results show that this strategy can decrease the amount of load shedding from 10.3 % to 6 % after commutation failure happens in UHV DC line connected to Henan province.