An intelligent control of photovoltaics is necessary to ensure fast response and high efficiency under different weather conditions. This is often arduous to accomplish using traditional linear controllers, as photovoltaic systems are nonlinear and contain several uncertainties. Based on the analysis of the existing literature of Maximum Power Point Tracking (MPPT) techniques, a high performance neuro-fuzzy indirect wavelet-based adaptive MPPT control is developed in this work. The proposed controller combines the reasoning capability of fuzzy logic, the learning capability of neural networks and the localization properties of wavelets. In the proposed system, the Hermite Wavelet-embedded Neural Fuzzy (HWNF)-based gradient estimator is adopted to estimate the gradient term and makes the controller indirect. The performance of the proposed controller is compared with different conventional and intelligent MPPT control techniques. MATLAB results show the superiority over other existing techniques in terms of fast response, power quality and efficiency.

No abstract

This study presents a novel three-level T-type isolated bidirectional DC-DC converter (3LTT-IBDC) for bidirectional DC power transfer. Owing to of the T-type structure of the proposed converter it has less number of switches and thus, lower cost and higher efficiency, as well as easy control are the advantages of the proposed converter compared to three-level counterparts. Additionally, 3LTT-IBDC is more reliable than three-level converters since unequal voltage blocking does not occur in T-type structure. Moreover, the symmetrical operation of the isolation transformer due to three-level symmetrical voltage waveform, lower voltage stress of switches and thus, higher efficiency are other advantages of 3LTT-IBDC compared to twolevel counterparts. Here, the DC voltage gain and power transfer characteristic of the proposed converter for steady-state operation and the expressions of the leakage inductance are derived. The proposed converter is simulated using PSIM. A 2-kW prototype is built to verify the theoretical analysis of the converter. Theoretical and experimental results show a good agreement and validate the competency of the presented converter design. The efficiency of the proposed converter and switching transitions of the switches are analysed. The full load and maximum efficiency of the converter are measured as 96.27% and 96.81%, respectively.

No abstract

This paper presents the Newton-Raphson approach using new equations to the power-flow analysis in steadystatefor multiterminal DC-A C s.. 'stems. A flexible and practical choice ofper-unit system is used toformulate the DC network and conve rter equations. A converter is represented by Norton '.I' equations ofa current source in parallel with the commutation resistance. Unlike in previous literature, the DC network equations are used to derive the controller equations for the DC system using a subset of specifications. The specifications considered are power at (/11 terminals except the slack terminal where the DC voltage specified. Similar Newton '.I' approach uses six variables per converter but this approach uses three variables per converter. This property provides less storage requirement and computation time than the others. Unlike the proposed paper, in some papers based on Newton's method, the main problem is that some of the diagonal elements oflacobi an matrix are weak and zero, and partial pivoting in the solution by triangular reduction is essential.