Research advances on renewable energy systems have increased the interest in the use of isolated power supplies composed of power converters based on high-frequency transformers. Such power equipment generally presents high internal impedance, which amplifies the effects of harmonic voltages produced by nonlinear loads that draw currents with high harmonic content. Some sensitive loads, e.g., electric motors and distribution transformers, may not properly operate when supplied by extremely distorted voltages. Series active power filters (SAPFs) are suitable to mitigate this inconvenient, being capable of providing harmonic voltage compensation and minimizing the distortion of supply voltages. In this context, this work addresses the small-signal modeling, control system implementation, and experimental validation of a single-phase SAPF. The proposed approach is solely employed for harmonic voltage compensation purposes, thus allowing loads to be supplied by a nearly sinusoidal voltage. During the modeling process, the operating steps are analyzed in detail, while the presence of parasitic elements is taken into account. An equivalent circuit is also derived, which is used to provide an easy understanding of the interactions among the SAPF, load, and power supply. From this model, transfer functions can be obtained so that it is possible to design the control loops used by the SAPF. Experimental results with distinct types of loads are presented to evaluate the SAPF performance in both steady-state and transient conditions. INDEX TERMS Harmonic voltage filtering, voltage quality, series active power filter, small-signal modeling, voltage-source inverter.
This work presents a review of the main topologies of switched capacitors (SCs) used in DC-DC power conversion. Initially, the basic configurations are analyzed, that is, voltage doubler, series-parallel, Dickson, Fibonacci, and ladder. Some aspects regarding the choice of semiconductors and capacitors used in the circuits are addressed, as well their impact on the converter behavior. The operation of the structures in terms of full charge, partial charge, and no charge conditions is investigated. It is worth mentioning that these aspects directly influence the converter design and performance in terms of efficiency. Since voltage regulation is an inherent difficulty with SC converters, some control methods are presented for this purpose. Finally, some practical applications and the possibility of designing DC-DC converters for higher power levels are analyzed.
This paper presents a new maximum power point tracking (MPPT) method based on the measurement of temperature and short-circuit current, in a simple and efficient approach. These measurements, which can precisely define the maximum power point (MPP), have not been used together in other existing techniques. The temperature is measured with a low cost sensor and the solar irradiance is estimated through the relationship of the measured short-circuit current and its reference. Fast tracking speed and stable steady-state operation are advantages of this technique, which presents higher performance when compared to other well-known techniques.
This paper presents a dynamic reconfiguration method for electrical connections in a Series-Parallel connected photovoltaic array under partial shading conditions. It is desirable to extract the maximum energy from the array, but it does not occur in situations where the modules have different points of operation caused by shading. The proposed method is then characterized by the maintenance of the PV array dimensions, that is; no module is removed or added to the array. Furthermore, the control algorithm is based on the Rough Sets Theory, which allows the fast and efficient implementation of a control system, comprising rules that identify the system optimal configuration.
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