Abstract
This paper proposes a symmetrical phase-locked loop (PLL) that can eliminate the frequency-coupling terms caused by the asymmetric dynamics of conventional PLLs. In the approach, a concept of complex phase angle vector with both real and imaginary phase components is introduced, which enables to control the direct- and quadrature-axis components with symmetrical dynamics. The small-signal impedance model that characterizes the dynamic effect of the symmetrical PLL on the current control loop is also derived, which, differing from the conventional multiple-input multiple-output impedance matrix, is in a single-input single-output (SISO) form based on complex transfer functions. This SISO representation allows for a design-oriented analysis. Moreover, the undesired sub-synchronous oscillation caused by the conventional asymmetrical PLL can be avoided, and the classical SISO impedance shaping can be utilized to cancel the negative resistor behavior caused by PLL; thus can greatly enhance the grid synchronization stability under weak grid conditions. The effectiveness of the theoretical analysis is validated by experimental tests.
Highlights
O VER the past decade, power electronic converters are increasingly used as the grid interface for renewable power sources and energy-efficient loads
It has been reported that the phase-locked loop (PLL) used for grid synchronization may bring a significant impact on the stability of the grid-connected converter, especially under the weak grid condition when the local voltage measured by the PLL is more influenced by the converter itself than by Manuscript received November 30, 2018; revised February 18, 2019; accepted May 14, 2019
The asymmetric dynamics of PLL characterized by the asymmetric multiple-input multiple-output (MIMO) matrix result in the frequency coupling effects in sequence domain, i.e., the one single-frequency perturbation imposed on the grid-connected converter will generate responses at two frequencies that are separated by twice fundamental frequency (2f1) [9]
Summary
O VER the past decade, power electronic converters are increasingly used as the grid interface for renewable power sources and energy-efficient loads. The asymmetric dynamics of PLL characterized by the asymmetric MIMO matrix result in the frequency coupling effects in sequence domain, i.e., the one single-frequency perturbation imposed on the grid-connected converter will generate responses at two frequencies that are separated by twice fundamental frequency (2f1) [9]. This frequencycoupling effect tends to introduce a sideband oscillation below. 3) SISO impedance shaping can be implemented to enhance the grid synchronization stability under the weak grid condition
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
