Abstract
The increasing use of multi-parallel grid-connected inverters introduces both high-quality and high-capacity power, while it tends to cause a resonance instability problem. A resonance damper can virtualize a resistor at resonant frequency to suppress the instability effectively, but the resonant frequency should be detected primarily. However, the resonant current or voltage is severely distorted and oscillating, which will lead to the resonant frequency extraction being more difficult. To address it, this paper proposes a resonance detection strategy based on the cascaded second-order generalized integrators (SOGI) and the normalized frequency locked loop (FLL). The cascaded structure ensures the accuracy by completely filtering the fundamental component from the detected voltage or current, and the normalization accelerates the frequency detection. The proposed method can be used as a crucial unit of the resonance damping controller. Finally, the performance of the proposed method is verified by the MATLAB-based simulation and Hardware-in-the-Loop (HIL)-based emulation results.
Highlights
In order to cope with climate change and the energy crisis, the renewable energy generation, especially the photovoltaic and wind power, is developing rapidly [1,2]
The technological advance of multi-parallel grid-connected inverters has promoted the rapid development of distributed generation, it results in a complex coupling relationship between the grid and inverters [5,6], which tends to bring about the resonance [7,8,9,10]
Through the verification of MATLAB simulation and HIL (Hardware-in-the-Loop)-based emulation, it can be seen that the proposed second-order generalized integrators (SOGI)-frequency locked loop (FLL) structure can effectively and quickly detect the resonant frequency in spite of the fact that the resonant frequency is uncertain and the signal to be detected is oscillating
Summary
In order to cope with climate change and the energy crisis, the renewable energy generation, especially the photovoltaic and wind power, is developing rapidly [1,2]. There are various techniques to estimate the frequency or phase, such as discrete Fourier transformation, Kalman filter, phase locked loop (PLL), Wavelet transformation, etc. Among these techniques, PLL receives wide attention because of its excellent performance and simple structure [14,15]. Discrete Fourier transformation and Wavelet transformation are often used to detect resonance frequency [16] The former divides the whole frequency band evenly, which means the information at the resonant point could be neglected . A typical multi-parallel grid-connected inverters system is modeled and analyzed, which will clarify the objective of resonance detection. Through the verification of MATLAB (vR2018b, Natick, MA, USA) simulation and HIL (Hardware-in-the-Loop)-based emulation, it can be seen that the proposed SOGI-FLL structure can effectively and quickly detect the resonant frequency in spite of the fact that the resonant frequency is uncertain and the signal to be detected is oscillating
Sign-in/Register to view highlights & summary 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.
