Investigation of single-stage transformerless buck–boost microinverters Derick Mathew, Rani Chinnappa Naidu Electrical Engineering, VIT University, Vellore, Tamil Nadu, India

Investigation of single-stage transformerless buck–boost microinverters Derick Mathew, Rani Chinnappa Naidu Electrical Engineering, VIT University, Vellore, Tamil Nadu, India

 Abstract: 

conventional microinverters with transformers and multiple-stage system increases the cost, weight and size, lowering the effectiveness and power density of PV system. It is therefore desirable to prevent using these methods for a microinverter. However, extra care must be taken to prevent component stress, excess switching and conduction losses, ground leakage currents and harmonics. Several transformerless buck–boost inverters have lately been suggested to address various issues. Due to the availability of a number of buck–boost inverter-topology for the solar PV system, it is often difficult to identify when to choose the appropriate topology. Therefore, in order to present a clear view of the advancement of transformerless buck–boost inverters for next-generation grid-integrated PV systems, this article seeks to explore multiple buck–boost topologies with an extensive analytical comparison. Computer simulations for the 70 W system have been conducted in PLECS software to strengthen the results and comparisons, as well as to provide more insight into the features of the distinct topologies for the building-integrated photovoltaic implementation. At the later part, voltage and current stress in each component, efficiency and total harmonic distortion of the system are provided with a general summary, as well as, a technology roadmap.

LINK WEB:

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2019.1237

Design and Implementation of a Low-cost Back-to-back Dynamic Voltage Restorer -Authors Chao-Tsung Ma and Yi-Hung Tian -Department of EE, CEECS, National United University, Taiwan

 

Design and Implementation of a Low-cost Back-to-back Dynamic Voltage Restorer Chao-Tsung Ma  and Yi-Hung Tian 

ABSTRACT

 The dynamic voltage restorer (DVR) is a power converter-based device widely used in power distribution systems to improve voltage quality. A conventional DVR includes an energy storage device (ESD) to provide the required power for a limited duration of voltage sag. However, the employment of ESD increases the DVR costs and limits its functionality. This research paper investigated a single-phase back-to-back DVR with simulation and small-scale hardware implementation. The proposed DVR includes two inverters connected in series and parallel with the distribution system, respectively, to enable bidirectional power flow. The advantage of this topology is its ability to compensate for longer voltage sags and swells, thus achieving a low-cost design. Using digital control scheme, the proposed DVR is able to perform multiple control functions simultaneously, including voltage swell/sag compensation, power factor correction (PFC), and harmonic current compensation. Based on the aforesaid, this paper reviews the related literature on DVR and then introduces the working principles of DVR and the proposed control scheme. Also, two sets of simulation studies and hardware tests were performed to do so. The typical results derived from the software simulation and small-scale hardware implementation are provided to verify the effectiveness of the proposed DVR and the related control scheme. Keywords: Dynamic Voltage Restorer (DVR); power quality control; back-to-back converter; digital controller.

LINK

https://jit.yuntech.edu.tw/2020/JIT-V02N02-08.pdf

Power Quality Renewable Energy Effective Use of Grid by Wind Intelligent Technique-Dr.P.Selvam, M.P.Sakthivel Professor & Head, Dept. of Electrical & Electronics Engineering, Vinayaka Mission's Kirupananda Variyar Engineering College, Salem, Tamil Nadu, India

 

Power Quality Renewable Energy Effective Use of Grid by Wind Intelligent Technique Dr.P.Selvam, M.P.Sakthivel Professor & Head, Dept. of Electrical & Electronics Engineering, Vinayaka Mission's Kirupananda Variyar Engineering College, Salem, Tamil Nadu, India 

Dept. of Electrical & Electronics Engineering, Vinayaka Mission's Kirupananda Variyar Engineering College, Salem, Tamil Nadu, India

 ABSTRACT: This present scenario we are facing a large amount of power crisis in our country to counteract this problem we are going for renewable energy, even though we are generating a power from solar and wind now no technique has been developed for efficient battery charging in PV/Grid connected solar UPS. This project deals with intelligent battery charging technique using SOC(State Of Charge) estimation so as to enhance the effective power utilization of solar panels and also the battery life. KEYWORDS: Effective battery charging, State of charge (SOC)

LINK: http://ijircce.com/admin/main/storage/app/pdf/6yYXHnZpbLo9pD2Ez15WidEc6hpklfNfY6FPERcJ.pdf

계통 연계형 인버터의 최적화된 LCL-필터 설계 기법- Optimization Design Method for LCL-filter in Grid-connected Inverter Systems -AUTHOR Seong Soo Park -Department of Space Survey Information Technology Ajou University--Dissertation for doctoral degree in engineering

 Optimization Design Method for LCL-filter in Grid-connected Inverter Systems

ABSTRACT 

Autrhor Seong Soo Park -Department of Space Survey Information Technology Ajou University

 Dissertation for doctoral degree in engineering 

This study proposes an optimized design method of LCL filter in grid connected inverter system using various pulse width modulation (PWM) methods. Recently, many contries around the world are implementing low carbon policies to prevent glob al warming. Importance of new renewable energy such as photovoltaic power , fuel cells and wind power generation is coming to the fore significantly . And also many countries are interested in the development of smart grid technology because it is necessary to develop a technology which connect s distributed power sources to power systems in order to introduce renewable energy. The Smart Grid means operating an effective power network by combining ICT (Information and Communication Te chnologies) with existing power grids. As the photovoltaic power generation and fuel cell power generation are DC power generation units , they are used in conjunction with the power grid like as electrical power system with converting DC to AC using inverter The harmonics is caused by switching control of the inverter and these harmonic components should be compiled with standard of IEEE (IEEE 519, IEEE 1547.2) and also THD (Total Harmonics Distortion) of output current should be limited to within 5 % based on this standard . For this reason, it is necessary to reduce harmonics by using filters at input and output sides of the inverter. In the past, L filter was used mainly , but drawback is increasing volume and weakness of dynamic characteristic as L filter capacity is increased. Therefore, recently LC filter or LCL filter are mainly used and various studies in terms of the filter design are under progressing. LCL filter has a combined structure with L filter and LC filter of inverter and has same characteristics with the third order low pass filter, furthermore same level of harmonics can be reduced with using only small capacity compared with L filter. However, there are some disadvantages that design is complicated and unwilling resonance might be happened. This paper proposes on optimized design method of the LCL filter based on the inverter topologies and switching methods. There is no different of design value from others in the low range of voltage modulating factor but the higher tolerance is happened, the bigger voltage modulating factor is incresead, This paper shows optimized design method related to this improvements. The simulations are carried out to verify the effectiveness of the proposed methods: 3 phase 2 level, 3 level topologies and SVPWM, DPWM switching methods for the grid connected inverter. Moreover, 3kW experimental setups are used to identify the feasibility of their methods.

LINK:  https://docsplayer.org/134883058-공학박사학위논문.html

SINGLE STAGE GRID-CONNECTED MICRO-INVERTER FOR PHOTOVOLTAIC SYSTEMS by Nikhil Sukesh-Department of Electrical and Computer Engineering--Queen’s University Kingston, Ontario, Canada-

 

SINGLE STAGE GRID-CONNECTED MICRO-INVERTER FOR PHOTOVOLTAIC SYSTEMS by Nikhil Sukesh 

 A thesis submitted to the Department of Electrical and Computer Engineering In conformity with the requirements for the degree of Master of Applied Sciences Queen’s University Kingston, Ontario, Canada 

 Abstract This thesis concentrates on the design and control of a single stage inverter for photovoltaic (PV) micro-inverters. The PV micro-inverters have become an attractive solution for distributed power generation systems due to their modular approach and independent Maximum Power Point Tracking (MPPT). Since each micro-inverter has an individual inverter section, it is essential to have small-sized power conversion units. Moreover, these inverters should provide large voltage amplification in order to connect to the utility grid because of the low voltages of the PV panels. In order to operate these inverters at high frequencies, the soft-switching of the power MOSFETs is an important criterion to minimize the switching losses during the power transfer. A novel Zero Voltage Switching (ZVS) scheme to improve the efficiency of a single stage grid-connected flyback inverter is proposed in this thesis. The proposed scheme eliminates the need for auxiliary circuits to achieve soft-switching for the primary switch. ZVS is realized by allowing the current from the grid-side to flow in a direction opposite to the actual power transfer with the help of bi-directional switches placed on the secondary side of the transformer. The negative current discharges the output capacitor of the primary MOSFETs thereby allowing turn-on of the switch under zero voltage. In order to optimize the amount of reactive current required to achieve ZVS a variable frequency control scheme is implemented over the line cycle. Thus the amount of negative current in each switching cycle is dependent on the line cycle. Since the proposed topology operates with variable frequency, the conventional methods of modeling would not provide accurate small signal models for the inverter. A modified state-space approach taking into account the constraints associated with variable switching frequency as well as the negative current is used to obtain an accurate small signal model. Based on the linearized inverter model, a stable closed loop control scheme with peak current mode control is implemented for a wide range of operation. The system incorporates the controllers for both the positive as well as negative peak of inductor current. Simulation and the experimental results presented in the thesis confirm the viability of the proposed topology.

LINK: https://qspace.library.queensu.ca/bitstream/handle/1974/7317/Sukesh_Nikhil_201207_MASC.pdf?sequence=1&isAllowed=y