Three-Phase VSC with Dedicated Positive and Negative Sequence Current Control

A three-phase Voltage Source Converter (VSC) with dedicated positive and negative sequence current control is a power electronic device capable of stable operation under unbalanced grid conditions. The core of this control strategy lies in decomposing three-phase currents into positive and negative sequence components and independently regulating them, effectively suppressing negative impacts caused by grid voltage asymmetry.

During grid voltage imbalances, conventional VSC control strategies may fail to simultaneously maintain stable active and reactive power output, potentially leading to current waveform distortion. The positive-negative sequence current control employs coordinate transformation and separation algorithms to independently adjust the magnitude and phase of positive and negative sequence currents, ensuring output current symmetry while maintaining DC-link voltage stability.

This control method typically involves a dual-loop control structure in the synchronous reference frame, where the inner loop handles current tracking and the outer loop manages power or voltage regulation. By incorporating sequence separation components, the control system can rapidly respond to grid disturbances, making it suitable for applications requiring high dynamic performance such as wind power integration and power quality management.

Another advantage of positive-negative sequence current control is its harmonic suppression capability. In severely harmonic-polluted environments, this strategy can be extended to multi-sequence component control for more precise current compensation, enhancing system immunity to disturbances. This technology has become a crucial solution in modern flexible AC/DC transmission systems and renewable energy generation systems.