Input Impedance Modeling and Verification of Single-Phase Voltage Source Converters Based on Harmonic Linearization

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Abstract
The impedance-based stability analysis of single-phase voltage source converters (VSCs) emphasizes the precise impedance modeling. Considering the complexity of dq-frame impedance modeling and measurement, this paper proposes a mirror-frequency impedance modeling and measurement approach of single-phase VSCs in the stationary frame based on harmonic linearization. First, the mirror-frequency definition is put forward and the dynamics of the second-order generalized phase-locked loop considering the mirror-frequency effects is validated by simulations. Next, the impedance model considering the mirror-frequency effects and dc-link voltage control loops is compared with the conventional one-dimension impedance model, and a mirror-frequency impedance measurement method is presented, which are verified by experiments on the hardware in the loop platform. The results indicate that the mirror-frequency impedance model considering the dc-link voltage control are more accurate and better captures the cross-coupling dynamics of VSCs. Finally, the different bandwidths of dc-link voltage control loops and different capacitances are designed to study the impacts of dc-link voltage control loops and ripples on impedance. The experiments and impedance-based analysis illustrate that the wider bandwidth of dc-link voltage control loops or the less capacitance with high dc-link voltage ripple will expand the frequency range of negative impedance in the low frequency.
Funding Information
  • National Nature Science Foundation (U1434203, U1734202)
  • Sichuan Province Youth Science and Technology Innovation Team (2016TD0012)

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