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In this article, a vector proportional–integral (VPI) current controller for the LC-coupling hybrid active power (LC-HAPF) with ideally zero steady-state error, optimal transient response, and good robustness is proposed. First, the transfer function of the proposed VPI current controller is introduced, and its parameter design for obtaining optimal transient response is discussed. Second, a detailed robustness analysis of the VPI current controller, including the system parameter variation, distorted grid voltage, and grid frequency variation conditions, is proposed. Third, the digital implementation method of the VPI controller and an overall control block diagram for the LC-HAPF with the proposed VPI current controller are presented. Moreover, a comparative study and analysis between the VPI current controller and the other representative current controllers under the minimum dc-link voltage is discussed in which the VPI current controller obtains the best performances under the minimum dc-link voltage operation. The simulation and experimental results are provided to verify the advantages and effectiveness of the proposed VPI current controller for a three-phase four-wire LC-HAPF in comparison with the other representative current controllers under different dc-link voltage conditions. Finally, the robustness under different grid conditions and unbalanced compensation capability of the proposed VPI-controlled LC-HAPF are also verified by the experimental results. [ABSTRACT FROM AUTHOR]

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]

Previous researches on space vector modulation (SVM) in active power filters (APFs) topologies find that compared with sinusoidal pulse width modulation, the SVM offers a better harmonic spectrum and has 15.47% more voltage utilization. The article not only proposes SVM for hybrid active power filters (HAPFs) but also answers the following questions. 1) Under what conditions both filters are equivalent to one another? 2) Which filter can enhance better tracking ability and better performance? 3) How the coupling component parameters and dc voltage affect the performance of both filters? The representative simulation and experimental results are given to verify the discussions. The conclusions can be application guidelines for the design of inductive and capacitive coupling inverters (e.g., APFs and HAPFs) in smart grids and development of energy internet due to their generalities to applications. [ABSTRACT FROM AUTHOR]