Abstract
Multi-parallel grid-connected voltage source inverters (VSIs) are widely applied in the fields of renewable energy, energy storage, harmonic suppression, etc. However, these inverters may cause harmonic stability problems due to the interactions among the grid-connected inverters through the grid impedance, which can seriously threaten system stability. The impedance-based stability criterion provides an effective tool for analyzing harmonic instability issues and can be divided into two types, namely, a ratio type and a sum type. Based on the existing studies of the sum-type criterion, this paper further proposes a new sum-type form based on the global admittance from the PCC to assess system stability through frequency-domain analysis. This global admittance-based stability criterion can be used not only to analyze system stability, but also to reveal the influence of each VSI unit on system stability with a lower computational burden and provide guidance for resonance suppression, especially in the case of a large number of grid-connected inverters and asymmetric inverter parameters. Finally, a MATLAB/Simulink model and 400 kVA/400 V experimental platform consisting of six grid-connected VSIs were established, and the corresponding results are presented to verify the effectiveness of the proposed method.
Highlights
A MATLAB/Simulink model and 400 kVA/400 V experimental platform consisting of six grid-connected voltage source inverters (VSIs) were established, and the corresponding results are presented to verify the effectiveness of the proposed method
The most common model of a power grid for stability analysis involves an admittance, Yg, in with an ideal voltage source, Vg, and a single grid-connected inverter can be represented as a current series with an ideal voltage source, Vg, and a single grid-connected inverter can be represented as a source, Is (s), in parallel with an output admittance, Yo (s)
The global admittance-based stability criterion has been proposed in this paper, which adopts the
Summary
To further study the application of the sum-type criterion in a multi-parallel grid-connected system, thisstudy paper the proposes a global stability. The stability can beother assessed the PCC is defined as theand summation of all the admittances, including the grid admittance, based on a frequency-domain analysis of global admittance. The stability can be assessed eigenvalue-based approach,analysis adding of or removing inverters has a minimal on the system model. Compared to effect the state-space model the approachapproach, is applicable to grid-connected systems This is aeffect global analysis and eigenvalue-based adding or removing inverters has amethod minimal onstability the system technique, there is applicable no need to analyze the stability of This eachmethod inverter, reduces the model. 4, the proposed global admittance-based stability criterion impedance-based the single grid-connected inverter system and multi-parallel is introduced.
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