Control of HVDC Light System Using Conventional and Direct Current Vector Control Approaches

With the advance of power electronic technology, the application of HVdc light systems based on voltage-source insulated gate bipolar transistor (IGBT) converters has increased rapidly in renewable, microgrid, and electric power systems. This paper proposes an optimal control strategy for an HVdc light system using a direct current vector control mechanism. The proposed approach is compared with the traditional vector control method for different HVdc control requirements, such as active power, reactive power, and grid voltage support control. A limitation of the conventional control mechanism is analyzed through a theoretical study and computer simulation. Closed-loop control evaluation demonstrates that the proposed approach works well for HVdc light system control both within and beyond the physical constraints of the system, such as rated power and saturation of pulse width modulation (PWM). The evaluation also shows that the conventional control technique could result in over voltage and system oscillation, especially when the controller operates beyond the PWM saturation limit.