A novel Lyapunov-based robust controller design for LCL-type shunt active power filters using adaptive sliding-mode backstepping approach

• Published in: e-Prime 2023-09, Vol.5, p.100200, Article 100200
• Main Authors: Hajbani, Vadood, Zakipour, Adel, Salimi, Mahdi
• Format: Article
• Language: English
• Subjects: Adaptive control; Digital signal processor (DSP); Hybrid control; LCL coupling; Nonlinear control; Robust control; Shunt active power filter (SAPF); Sliding mode control (SMC); Uncertain parameters
• ISSN: 2772-6711; 2772-6711
• DOI: 10.1016/j.prime.2023.100200

•In this paper:•Hybrid adaptive-robust nonlinear controller is developed for active power filters with LCL coupling.•All uncertain parameters of the model including the DC link capacitor and equivalent impedances of the LCL coupling network are estimated by employing a proper Lyapunov function.•Based on the experimental results, it is observed that the steady-state error of the proposed nonlinear controller is zero in a wide range of operations.•Despite using a local load with a very high current THD value (about 51%), the developed controller is capable of maintaining the grid current THD within the standard range (around 1%). Moreover, it is shown that the THD improvement of the proposed controller is more efficient than the previous studies. In this paper, a novel hybrid two-loop nonlinear controller is designed for stabilization and robust control of the LCL-type shunt active power filter (SAPF). To cope with the instability issue of the closed-loop system and the inherent resonance of the LCL coupling, backstepping, sliding mode and adaptive controllers are combined. DC link voltage of the grid-connected inverter is regulated in an outer control loop by determining a proper reference value for an inner loop. In addition to DC link voltage control, a major objective of the proposed closed-loop system is to make the grid current in phase with the grid voltage directly. Hence, active power filtering of the grid-connected inverter can be achieved without any current feedback from the local load. To stabilize the LCL-type SAPF in a wide range of changes, all uncertain parameters of the model including the DC link capacitor and equivalent impedances of the LCL coupling network are estimated by employing a proper Lyapunov function. For practical evaluation of the developed approach, the closed-loop system is implemented by using Texas Instruments’ digital signal processor (DSP-TMS28F335). Considering the application of an adaptive-robust nonlinear controller, it is proved that the system enjoys a stable and robust performance over the whole range of utilization, and it doesn't suffer from resonance issues of the LCL-type SAPFs. Moreover, considering the experimental results, it is observed that the steady-state error of the proposed nonlinear controller is zero in a wide range of operations.