A Theoretical Concept of Decoupled Current Control Scheme for Grid-Connected Inverter with L-C-L Filter

This paper proposes a nonlinear decoupled current control scheme for a grid-connected inverter with LCL filter. Decoupling the active and reactive current control channels is one of the main demands in the control of inverters. For inverters with an L filter, the decoupling can be achieved by a prop...

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Bibliographic Details
Published in:Applied sciences 2021-07, Vol.11 (14), p.6256
Main Authors: Ghasemi, Mohamad Amin, Zarei, Seyed Fariborz, Peyghami, Saeed, Blaabjerg, Frede
Format: Article
Language:English
Subjects:
back-stepping control
Case studies
Channels
Control algorithms
Control methods
Control systems design
Control theory
Controllers
Converters
decoupled current control
Decoupling
Equations of state
Inverters
LCL-type filter
Methods
Nonlinear control
renewable energy
Robust control
Sensors
Stability analysis
Systems stability
voltage source inverter
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Summary:This paper proposes a nonlinear decoupled current control scheme for a grid-connected inverter with LCL filter. Decoupling the active and reactive current control channels is one of the main demands in the control of inverters. For inverters with an L filter, the decoupling can be achieved by a proper feed-forward of grid voltages. However, the coupling of channels is a complex issue for converters with LCL filters. The resonance mode of the LCL filter may cause instability, which adds more complexity to the analysis. In this paper, state equations of the system are provided, which highlight the coupling between active and reactive currents injected into the grid. Accordingly, a non-linear control scheme is proposed which effectively decouples the channels and dampens the resonant modes of the LCL filter. The stability of the proposed control method is verified by the Lyapunov criterion. Independency of the system stability to the grid-impedance is another feature of the proposed approach. Moreover, only grid-side currents are needed for implementation of the proposed scheme, avoiding the need for additional current sensors for the output capacitor and grid-side inductor. For accurate modelling of the inverter, the computation and PWM sampling delays are included in the controller design. Finally, various case studies are provided that verify the performance of the proposed approach and the stability of the system.
ISSN:2076-3417
2076-3417
DOI:10.3390/app11146256