Summary In this study, a nonlinear control of a 5‐level T‐type converter topology‐based multiterminal voltage source converter high‐voltage direct current system is proposed. The idea of the proposed control is to combine the backstepping control and direct power control with virtual flux concept into one controller able to improve the performance of the transmission system. In the other side, the use of a 5‐level space vector modulation with a balancing strategy based on effective use of the redundant switching states of the converters voltage vectors guarantees the objective of maintaining balanced voltages in DC‐capacitors. Finally, simulations of the 5‐level T‐type multiterminal voltage source converter high‐voltage direct current system validate the effectiveness of the proposed control law. The obtained results are compared with those performed by a conventional Proportional Integrator (PI) controller. These outcomes allow to exhibit excellent transient response during a range of operating conditions.

This paper proposes a Virtual Flux Predictive Direct Power Control (PDPC) for a five-level T-type multi-terminal Voltage Source Converter High Voltage Direct Current (VSC-HVDC) transmission system. The proposed PDPC scheme is based on the computation of the average voltage vector using a virtual flux predictive control algorithm, which allows the cancellation of active and reactive power tracking errors at each sampling period. The active and reactive power can be estimated based on the virtual flux vector that makes AC line voltage sensors not necessary. A constant converter switching frequency is achieved by employing a multilevel space vector modulation, which ensures the balance of the DC capacitor voltages of the five-level t-type converters as well. Simulation results validate the efficiency of the proposed control law, and they are compared with those given by a traditional direct power control. These results exhibit excellent transient responses during range of operating conditions.

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