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In this article, a second-order sliding-mode control (SOSMC) based on supertwisting controller for LC-coupling hybrid active power filter (LC-HAPF) is proposed. Among the literatures review studies, hysteresis-based current controller, which is a special implementation of sliding-mode control, is usually used due to its simplicity, robustness, and good dynamic performance for reference tracking. However, it generates a nonfixed switching frequency for the power filter, which leads to undesirable harmonics problem. The proposed SOSMC ensures the good robustness and dynamic performance of using the conventional sliding mode control with an improved steady-state performance and disturbance rejection capability. In addition, with the help of supertwisting controller, the proposed SOSMC can achieve fixed switching frequency characteristic. First, the control objective and the design methodology of sliding surface are discussed and given in this article. Second, a detailed parameter design procedure under stability, system parameter variation, distorted grid voltage, and grid frequency variation consideration is provided. Then, experimental results on a three-phase four-wire LC-HAPF are carried out to verify the steady-state and dynamic performances of the proposed SOSMC compared with other representative current controllers. Finally, the disturbance rejection capability under different grid conditions of the proposed SOSMC is also verified by experimental results. [ABSTRACT FROM AUTHOR]

A finite-set model predictive control (FS-MPC) with coupling capacitor voltage observer scheme is proposed for thyristor-controlled LC-coupling hybrid active power filter (TCLC-HAPF) in this article. It ensures the fast transient response, low steady-state error, and good robustness under both inductive and capacitive load situations. Generally, the implementation of FS-MPC for TCLC-HAPF requires sensing of coupling capacitor voltage and thyristor-controlled reactor current in addition to sensing load voltage, load current, and compensation current, which increases the system complexity and cost. To relax this problem, the simplified predictive model is first proposed, thus reducing the required sensing signals and system order. Then, a coupling capacitor voltage observer is utilized to reduce the hardware costs, which can obtain a comparable performance with directly sensed capacitor voltage. The delay compensation is also considered for the control delay in practical realization. Finally, the effectiveness and performance of the FS-MPC with coupling capacitor voltage observer for TCLC-HAPF are verified by simulated and experimental results. [ABSTRACT FROM AUTHOR]

Compared with the conventional active power filter, the thyristor-controlled LC-coupling hybrid active power filter (TCLC-HAPF) has a distinct characteristics of low dc-link operating voltage, which can lower the system and operational costs in the medium-voltage-level system. It also has a wider operational range than the conventional hybrid active power filter. Besides that, the TCLC-HAPF can provide reactive, harmonic, and unbalanced powers compensation simultaneously. In this article, the modeling of the TCLC-HAPF is investigated based on the linear control aspect. Then, the analysis, design, and implementation of a multi-quasi-proportional-resonant (MQPR) controller with gain scheduling for the TCLC-HAPF will be proposed, which can automatically change the resonant gain between the inductive and capacitive loads operation to improve its compensation performances. The proposed controller can significantly reduce the TCLC-HAPF steady-state current tracking errors and output current ripple. Finally, the simulation and experimental results are also provided to verify the effectiveness and performance of the MQPR controller for the TCLC-HAPF in comparison with the hysteresis current controller and quasi-proportional-resonant (QPR) controller, which shows superior compensating performances. [ABSTRACT FROM AUTHOR]