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This paper proposes a robust design for the ac/ac chopper-based voltage sag/swell compensation systems. This includes the design of a new buck-boost topology and the application of a robust switching scheme for a voltage compensator. The proposed circuit can operate in the buck or boost mode for both the sag and the swell compensations. A control scheme for a fast compensation is also proposed which is suitable for the ac/ac chopper-based compensation system. Detailed analysis and verification through a simulation in the MATLAB are presented highlighting the advantages of the proposed technique. An experimental verification has also been performed by using a laboratory prototype system. [ABSTRACT FROM AUTHOR]

A novel hybrid active power filter (HAPF) topology is proposed, which shows advantages of the conventional HAPF and the LCL filter in terms of reduced dc-link voltage, lower switching ripples, and less electromagnetic interference injection. To enhance the noise rejection capability of the digital controller, the resetting filters (RFs) are utilized as prefilters before the analog/digital sampling stage. A robust deadbeat current control law is derived based on the average current tracking scheme, where the effect of the RFs is favorably incorporated. To alleviate the difficulties in current controller design, the ac-side capacitor voltage of the HAPF is estimated by using the adaptive linear neural network identifier in the load current feedforward loop. Hence, a simple proportional controller is utilized in the inner current loop. Moreover, the grid current feedback and load current feedforward strategies are used to achieve precise current tracking and fast dynamic response. A 75-kVA prototype system is built for verification. The validity of the proposed HAPF and its control algorithms are confirmed by the experimental results. [ABSTRACT FROM AUTHOR]

Several ZVS/ZCS (zero voltage switching/zero current switching) snubbers have been proposed in the past to minimize the losses and EMI in boost PFC. In these topologies, the commutation energies are reflected to the load or source to achieve energy conservation. However, this energy can also be utilized in a way to further improve the performance of the PFC and this paper is a first step in this direction. Here, we will propose a new topology to minimize the crossover distortion in boost rectifier. The main characteristic of the proposed topology besides ZCS/ZVS switching is that it also improves the crossover distortion. A prototype system was built and tested to verify the proposed topology. [ABSTRACT FROM AUTHOR]

This study is dedicated to establishing a comparative analysis of the performance of different local controllers on the cooperative control of DC microgrids. One of the elementary and challenging issues in DC microgrids is the assurance of fairness in proportional current sharing while accomplishing voltage regulation in parallelly connected distributed energy sources. In this work, structural improvements are proposed to enhance the system stability and control performance. A finite-gain controller was employed in the outer voltage control loop with a simple proportional (P) controller in the inner current control loop of a converter. Due to the finite-gain controller, droop-like power sharing was achieved without droop coefficient. In order to further enhance the power-sharing accuracy and DC voltage regulation, a different method was adopted in consensus-based cooperative control to estimate the average current and average voltage difference. Moreover, small signal analysis was used to scrutinize the stability and control performance of the local controller, while different communication delays and current disturbances were applied to examine the performance of the controller. Finally, a four-node-based DC microgrid setup was developed in MATLAB/Simulink environment, and simulation results of the proposed and existing techniques were scrutinized. The simulations results demonstrated the effectiveness of the proposed controller. [ABSTRACT FROM AUTHOR]