TY - JOUR
T1 - Advanced sensorless nonlinear control and stability analysis of single-stage PV systems connected to the grid via a 3L-NPC inverter
AU - Mchaouar, Youssef
AU - Abouelmahjoub, Youness
AU - Abouloifa, Abdelmajid
AU - Abouobaida, Hassan
AU - Lachkar, Ibtissam
AU - Giri, Fouad
AU - Taghzaoui, Chaimaa
AU - Elallali, Aicha
AU - Guerrero, Josep M.
N1 - Publisher Copyright:
© 2023 European Control Association
PY - 2024/1
Y1 - 2024/1
N2 - This paper proposes a novel control strategy for a single-stage photovoltaic (PV) system consisting of two PV panels connected to the grid via a three-level neutral point clamped converter topology with an LCL filter. This control method is based on a developed 5th order model containing sum and difference terms of the voltages of the two input capacitors. This allows decoupling the issues of maximum power point tracking and power factor correction from the issue of balancing the power exchange generated by the panels, which facilitates control design and improves system performances. The control problem under consideration is dealt with using a non-linear controller composed of three loops: (i) an inner loop is developed, based on backstepping and Lyapunov approaches, to correct the power factor by forcing the grid current to be sinusoidal and in phase with the grid voltage; (ii) an outer loop is designed, using a filtered proportional-integral controller, to regulate the DC bus voltage to a climate-dependent reference; (iii) a balancing loop is designed, using a proportional-integral controller, to cope with the neutral point voltage balancing problem. The proposed controller also includes a state observer that provides on-line estimation of the network state variables that are not accessible to measurements. Another important aspect of this work is the development of a formal, complete and rigorous analysis in order to describe the performance and analyse the stability of the closed-loop system using various analytical tools, including averaging theory, Routh criteria and indirect Lyapunov stability. A simulation in MATLAB/SIMULINK environment shows, on the one hand, the efficiency and robustness of the proposed nonlinear controller against changing climatic conditions and, on the other hand, the superiority of this control strategy compared to the one based on a PI linear inner loop controller for the studied system with an L- filter and an LCL filter.
AB - This paper proposes a novel control strategy for a single-stage photovoltaic (PV) system consisting of two PV panels connected to the grid via a three-level neutral point clamped converter topology with an LCL filter. This control method is based on a developed 5th order model containing sum and difference terms of the voltages of the two input capacitors. This allows decoupling the issues of maximum power point tracking and power factor correction from the issue of balancing the power exchange generated by the panels, which facilitates control design and improves system performances. The control problem under consideration is dealt with using a non-linear controller composed of three loops: (i) an inner loop is developed, based on backstepping and Lyapunov approaches, to correct the power factor by forcing the grid current to be sinusoidal and in phase with the grid voltage; (ii) an outer loop is designed, using a filtered proportional-integral controller, to regulate the DC bus voltage to a climate-dependent reference; (iii) a balancing loop is designed, using a proportional-integral controller, to cope with the neutral point voltage balancing problem. The proposed controller also includes a state observer that provides on-line estimation of the network state variables that are not accessible to measurements. Another important aspect of this work is the development of a formal, complete and rigorous analysis in order to describe the performance and analyse the stability of the closed-loop system using various analytical tools, including averaging theory, Routh criteria and indirect Lyapunov stability. A simulation in MATLAB/SIMULINK environment shows, on the one hand, the efficiency and robustness of the proposed nonlinear controller against changing climatic conditions and, on the other hand, the superiority of this control strategy compared to the one based on a PI linear inner loop controller for the studied system with an L- filter and an LCL filter.
KW - Backstepping
KW - MPPT
KW - Neutral-point-clamped multilevel converter
KW - Photovoltaic system
KW - Power factor correction
KW - Stability analysis
UR - http://www.scopus.com/inward/record.url?scp=85173213561&partnerID=8YFLogxK
U2 - 10.1016/j.ejcon.2023.100907
DO - 10.1016/j.ejcon.2023.100907
M3 - Journal article
AN - SCOPUS:85173213561
SN - 0947-3580
VL - 75
JO - European Journal of Control
JF - European Journal of Control
M1 - 100907
ER -