Abstract
Grid-connected inverters are an important part of the connection between distributed power generation units and the large grid, and their stability is the basis for ensuring the safe operation of distributed power generation units. This study found that there is an inherent digital control delay in the three-phase LCL grid-connected inverter system. This characteristic causes the effective range of capacitive current feedback active damping to be reduced, the selection range of the active damping coefficient to be limited, and the phase at the open-loop cutoff frequency to be reduced. In order to reduce the impact of digital delay, this article conducts a detailed analysis of the characteristics of the first-order lead link that can be used as delay compensation, pointing out that its infinite gain when it obtains the optimal compensation effect will bring noise to the inverter system. This paper proposes a method of cascading digital filters for the first-order leading link to suppress its infinite gain. An improved delay compensation link that is more suitable for numerically controlled inverter systems is constructed. Finally, the effectiveness and necessity of the proposed improved delay compensation link are verified by a simulation platform and an experimental platform.
Highlights
LCL-type grid-connected inverters have the advantage of a better harmonic filtering effect; as such, the stability of LCL-type grid-connected inverters has been studied and given attention by many scholars [1,2]
13a shows the grid current waveform when the improved delay compensation link is not added in the weak grid, and the harmonic content is relatively large at this time
12b shows the grid-connected inverter system current active phase grid current waveform, the grid current waveform, and the voltage waveform damping method suppresses the inherent resonance of the LCL filter while improving the at steady state after effect
Summary
LCL-type grid-connected inverters have the advantage of a better harmonic filtering effect; as such, the stability of LCL-type grid-connected inverters has been studied and given attention by many scholars [1,2]. Due to the equivalent delay in digital control, the equivalent impedance of capacitive current feedback active damping changes with the change of frequency [11], and its effective range of resonance spike suppression is reduced. In Wang et al [20], the method of reducing the delay compensation effect is adopted to avoid the infinite gain of the first-order lead link near the Nyquist frequency. This paper constructs an improved delay compensation link that is more suitable for digital control grid–connected inverter systems by cascading zerophase-shift digital filters While this link extends the effective range of active damping, it does not affect the amplitude of the grid-connected inverter system, avoids noise at the Nyquist frequency, and improves the stability of the system. The validity of the theoretical analysis is verified through a simulation platform and an experimental platform
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
