Output Current Quality Improvement for VSC With Capability of Compensating Voltage Harmonics

Using the voltage source converter (VSC) to compensate for voltage harmonics at the point of common coupling (PCC) is beneficial for the power supply quality in the regional power grid. However, it leads to a significant deterioration of output current quality for VSC. This article aims to develop the design principle and realization method for impedance reshaping in VSC used for compensating voltage harmonics with the minimal sacrifice of the output current quality. By revealing the coupling constraint between the voltage harmonics of PCC and the output current harmonics of VSC, a harmonics impedance design principle for VSC is proposed. This principle indicates that the impedance phase of VSC should be identical to the phase of grid impedance at the frequency of harmonics. Hence, an impedance reshaping strategy based on the variable-phase reduced-order generalized integrator is developed, which can reshape the VSC's impedance to fulfill the harmonics impedance design principle under different grid conditions. Compared to existing studies, the proposed harmonics impedance design principle and realization method meet the same requirement of the voltage quality at PCC with a lower VSC's output current quality sacrifice. Theoretical analysis and experiments are presented to verify the effectiveness of the proposed strategy.