Output-feedback control of a grid-connected photovoltaic system based on a multilevel flying-capacitor inverter with power smoothing capability

With the large-scale integration of renewable energy systems, the power inertia and voltage support of the grid are low. Using the inverter with temporary storage capabilities cope with shortages and power fluctuations. This paper presents a new sensorless control of a single-phase grid-connected PV system based on a multilevel flying capacitor inverter MFCI) able to smooth out the power produced. The designed controller involves two cascade loops, an outer loop control extracts the maximum power despite climate change, and an inner loop consists of a model predictive control based on the Lyapunov theory for power factor correction and flying capacitor voltage balancing. Furthermore, an interconnected Kalman-like high-gain observer is combined with the predictive control algorithm to estimate the flying capacitor voltages accurately based on the actual grid current. The stability study of the suggested observer in the closed loop has been described. An algorithm that generates reference signals to manage power flows is also developed. The performance of the proposed controller has been verified on the MATLAB/Simulink platform, and the simulation results confirm the effectiveness of the proposed controller over different grid operating modes. •the proposed PV system is based on MFC inverter able to smooth out the grid-injected power.•The designed controller combines a Lyapunov-based model predictive control with a Kalman-like high-gain observer.•The PV conversion system optimizes energy extraction, injecting it smoothly into the grid.•The inverter, with temporary storage, copes with power fluctuations without external energy storage during grid faults.•The closed-loop stability of the controller is rigorously proved during the normal mode and grid fault conditions.