An impedance-based active-filter additional control method of PWM-converters to mitigate voltage unbalance and harmonics

This paper proposes an impedance-based active-filter additional control method for grid connected PWM-converters, by which a PWM-converter can help improve the voltage quality at a sensitive load bus (SLB) of a complex network with many distributed unbalanced loads and nonlinear loads. To realize the method, the information of the voltage to be compensated needs to be acquired and transferred to the converter. Then the information will be utilized to calculate the grid impedance parameters and generate the optimized harmonic current reference and fundamental negative sequence current reference of the converter online. The proposed method has no influence on the basic power conversion function of the converter, and shows better power quality control performance than traditional local load compensation method, so it is meaningful for improving the cost-effectiveness of power quality improvement and promoting the application of renewable energy.