Optimal delay compensation method for active damping of LCL-type converter

Abstract

The invention discloses an optimal delay compensation method for active damping of an LCL-type converter. The method includes determining the delay time of a system to acquire an active damping control model; simplifying the active damping control model, and calculating the virtual impedance generated by an inner loop delay to acquire a resonance peak and the reason why the resonance frequency isaffected by the delay; from the perspective of resonance inhibition, determining the optimal compensation method: feedback coefficients plus lead phase compensation; designing a lead compensation device, determining the feedback coefficients, comparing the ideal and the corrected amplitude-frequency response figures, and verifying the optimality to acquire the optimal amplitude-frequency responsefigures. The optimal delay compensation method has the advantages that resonance frequency shifting and resonance peak amplification both caused by the delay during the active damping control can be suppressed, the stability margin of the system is improved, and the attenuation ability of the LCL to high-frequency harmonic waves and the high anti-interference ability to the grid-side impedance fluctuations are guaranteed.

Description

technical field [0001] The invention relates to the technical field of new energy grid connection, in particular to an optimal delay compensation method for active damping of an LCL converter. Background technique [0002] Distributed generation systems (DPGS) based on renewable energy sources, such as wind and solar energy, have attracted increasing attention due to their environmentally friendly properties. As the interface between DPGS and the grid, the grid-connected converter plays an important role in injecting high-quality power into the grid. Grid-connected converters usually use L filters or LCL filters to attenuate switching harmonics. Compared with the L filter, the LCL filter has the advantages of small size and strong attenuation ability to high-frequency switching ripple, so it has been widely used, but the LCL filter itself has resonance, which is easy to cause system instability. There are passive damping methods and active damping methods to suppress reson...

AI Technical Summary

Problems solved by technology

So far, the design of LCL grid-connected converters either does not consider the influence of delay on resonance, or performs delay compensation for the purpose of improving the stability margin of the system, without considering the fluctuation of resonance frequency and the increase of resonance peak And the weakening of high-frequency harmonic filtering ability, the optimal effect of delay compensation cannot be achieved

In addition, for the system after delay compensation, neither the phase margin nor the amplitude margin can be used as a scalar to determine the stability of a system, and optimal compensation cannot be achieved.

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