Abstract
This article presents an effective resonance suppression control for grid-interactive inverters with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter in weak grid conditions. The resonance suppression mechanism is based on an adaptive model predictive control (AMPC). The large parasitic impedance and low short-circuit ratio (SCR) of weak grid challenges the operation of grid-interactive inverters. Specifically, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filter resonance may get excited, resulting in collapse of the inverter operation. The proposed AMPC scheme autonomously alter the controller objectives for suppressing the resonance. The proposed control scheme alters the feedback currents based on the grid-condition. During the stiff grid conditions, grid current serves as feedback to the controller. While in the weak grid conditions, the inverter current is selected as feedback signal. The toggling action between these two feedback currents is determined by comparing moving RMS of grid current with desired current as constraint in the proposed AMPC cost function. The performance of proposed controller is verified experimentally. The results demonstrate that the proposed controller features robust performance under various grid conditions, model parameter mismatch, grid disturbances, seamless transition between controller modes of operation and feedback alteration to attain resonance suppression, eliminates required tuning efforts in comparison to classical multi-nested loop control schemes, and provides high power quality according to IEEE standard 1547.
Highlights
Distributed energy resource (DERs) such as PV system are integrated with grid through power electronic interfaces
This paper proposes an adaptive model predictive control (AMPC) scheme for the resonance suppression of LCL filterbased inverters interacting with weak grid
Where i1 is the inverter current, Rf is the equivalent series resistance (ESR) of the filter capacitor, vc is the voltage across the shunt branch’s filter capacitor, vinv is the bridge voltage, determined by ѱt feasible switching states ig is the grid current, which is equal to ipcc, vpcc is the voltage at point of common coupling (PCC), L1 is the inverter side inductance, L2 is the grid side inductance
Summary
Distributed energy resource (DERs) such as PV system are integrated with grid through power electronic interfaces. According to [18], without taking time delay into consideration, under weak grid conditions utilizing inverter current feedback (ICF) in control loop increases the stability margin. This is because of inherent damping feature of ICF that divulge under weak grid conditions. This paper proposes an adaptive model predictive control (AMPC) scheme for the resonance suppression of LCL filterbased inverters interacting with weak grid. The main contribution of this work is to integrate the dual state variable feedback approach with MPC framework to leverage MPC features for more reliable resonance suppression in a straightforward manner without requirement of significant tuning effort.
Sign-in/Register to view highlights & summary 
Published Version (
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