scholarly journals An effective fault management scheme and comprehensive double line‐frequency ripple propagation analysis for MVDC networks

2021 ◽  
Author(s):  
Dongsen Sun ◽  
Xiaonan Lu ◽  
Liang Du ◽  
Fei Lu
Keyword(s):  
Fault Management ◽  
Double Line ◽  
Line Frequency ◽  
Management Scheme ◽  
Propagation Analysis

scholarly journals PV Micro-Inverter Topology Using LLC Resonant Converter

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3106 ◽  
Author(s):  
Hiroki Watanabe ◽  
Jun-ichi Itoh ◽  
Naoki Koike ◽  
Shinichiro Nagai
Keyword(s):  
Conversion Efficiency ◽  
Power Converter ◽  
Electrolytic Capacitor ◽  
Resonant Converter ◽  
Double Line ◽  
Line Frequency ◽  
Point Tracking ◽  
Llc Resonant Converter ◽  
Frequency Power ◽  
Micro Inverter

In this paper, a DC–single-phase AC power converter with an LLC resonant converter is presented for a photovoltaic (PV) micro-inverter application. This application requires the leakage current suppression capability. Therefore, an isolated power converter is usually combined for DC/AC systems. The LLC resonant converter is the one of the isolated power converter topologies, and it has good performance for conversion efficiency with easy control. On the other hand, a double-line frequency power ripple has to be compensated for in order to improve the performance of the maximum power point tracking (MPPT). Therefore, a bulky electrolytic capacitor is usually necessary for the power converter. However, the electrolytic capacitor may limit the lifetime of the micro-inverter. This paper introduces the PV micro-inverter with a LLC resonant converter. In addition, the active power decoupling circuit is applied in order to compensate the double-line frequency power ripple by the small capacitor in order to eliminate the electrolytic capacitor. Finally, the transformer design is considered in order to reduce the transformer losses. As a result, the conversion efficiency of the LLC converter is improved by 1% when the litz wire has many strands.

scholarly journals Classification of Three-Phase Grid-Tied Microinverters in Photovoltaic Applications

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2929
Author(s):  
Ahmed Shawky ◽  
Mahrous Ahmed ◽  
Mohamed Orabi ◽  
Abdelali El Aroudi
Keyword(s):  
Single Phase ◽  
Double Line ◽  
Line Frequency ◽  
Point Tracking ◽  
Power Point Tracking ◽  
Pv Module ◽  
Three Phase ◽  
Power Point ◽  
Pv Grid

Microinverters are an essential part of the photovoltaic (PV) industry with significant exponential prevalence in new PV module architectures. However, electrolyte capacitors used to decouple double line frequency make the single-phase microinverters topologies the slightest unit in this promising industry. Three-phase microinverter topologies are the new trend in this industry because they do not have double-line frequency problems and they do not need the use of electrolyte capacitors. Moreover, these topologies can provide additional features such as four-wire operation. This paper presents a detailed discussion of the strong points of three-phase microinverters compared to single-phase counterparts. The developed topologies of three-phase microinverters are presented and evaluated based on a new classification based on the simplest topologies among dozens of existing inverters. Moreover, the paper considers the required standardized features of PV, grid, and the microinverter topology. These features have been classified as mandatory and essential. Examples of the considered features for classifications are Distributed Maximum Power Point Tracking (DMPPT), voltage boosting gain, and four-wire operation. The developed classification is used to identify the merits and demerits of the classified inverter topologies. Finally, a recommendation is given based on the classified features, chosen inverter topologies, and associated features.

scholarly journals Development of a DC-Side Direct Current Controlled Active Ripple Filter for Eliminating the Double-Line-Frequency Current Ripple in a Single-Phase DC/AC Conversion System

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4772
Author(s):  
Ying-Chieh Chen ◽  
Liang-Rui Chen ◽  
Ching-Ming Lai ◽  
Yuan-Chih Lin ◽  
Ting-Jung Kuo
Keyword(s):  
Energy Source ◽  
Steady State ◽  
Single Phase ◽  
Current Control ◽  
Control Loop ◽  
Double Line ◽  
Line Frequency ◽  
Conversion System ◽  
Current Ripple ◽  
Frequency Current

The objective of this paper is to propose an active ripple filter (ARF) using the patented DC-side direct current control for eliminating the double-line-frequency current ripple in a single-phase DC/AC conversion system. The proposed ARF and its control strategies can not only prolong the usage life of the DC energy source but also improve the DC/AC system performance. At first, the phenomena of double-line-frequency current ripple and the operation principle of the ARF are illustrated. Then, steady-state analysis, small-signal model, and control loop design of the ARF architecture are derived. The proposed control system includes: (1) a DC current control loop to provide the excellent ripple eliminating performance on the output of the DC energy source; (2) a voltage control loop for the high-side DC-bus voltage of the ARF to achieve good steady-state and transient-state responses; (3) a voltage feedforward loop for the low-side voltage of the ARF to cancel the voltage fluctuation caused by the instability of the DC energy source. Finally, the feasibility of the proposed concept can be verified by the system simulation, and the experimental results show that the nearly zero double-line-frequency current ripple on the DC-side in a single-phase DC/AC conversion system can be achieved.

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