Distributed Fixed-Time Secondary Frequency Control of MTDC systems

In this paper, fixed-time distributed control of MT-DC systems is presented for secondary frequency control. A fixed-time observer is constructed to estimate the synchronization error, and a fast fixed-time controller is designed to achieve fixed-time terminal frequency synchronization of each distributed generator and provide proportional active power distribution. The secondary control of each converter consists of a fixed-time consensus based frequency regulator that uses relative information from the neighboring AC areas which requires sparse communication links. Compared with the existing controllers, the proposed distributed control scheme guarantees fixed-time convergence of the synchronization error, independent of the initial conditions, allowing the stabilization time to be pre-designed offline according to the requirements in MTDC systems. In addition, the stability of the method is verified by Lyapunov function. Simulation results validate the effectiveness of the proposed control scheme.