International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 11 Issue: 04 | April 2024
p-ISSN: 2395-0072
www.irjet.net
ANALYSIS AND MINIMIZATION OF LEAKAGE CURRENT IN THE PV GRID CONNECTED CASCADED MULTI LEVEL INVERTER T. SREENU1, CH. JAYA SREE2, A. MADHAN KUMAR3, B. SRINUVASA RAO4, P. PRASANTH KUMAR5 1Assistant professor, EEE, Visakha institute of engineering & technology, Visakhapatnam, Andhra Pradesh, India 2,3,4,5UG Student, EEE, Visakha institute of engineering & technology, Visakhapatnam, Andhra Pradesh, India
---------------------------------------------------------------------***--------------------------------------------------------------------The significant leakage current in transformer less PV Abstract - Common-mode voltage pulse width modulation
systems, however, poses a major safety hazard. The PV leakage current might go directly to the grid if galvanic isolation is not used [4]. Stray capacitance is produced when the PV is grounded. A large amount of current leaks out because the stray capacitance charges and discharges due to the changing potential. In addition to posing a safety risk, a large leakage current will reduce the PV system's efficiency by amplifying losses, electromagnetic interference, and grid current ripples [5].
techniques have been suggested recently to reduce the leakage current in single-phase transformer less photovoltaic (PV) systems. The majority of these studies, however, have ignored other aspects of PV system performance, including cost, voltage linearity, harmonic distortion, DC-link current ripples, and the reduction of leakage current. This paper focuses on a five-level inverter that doesn't need a transformer for gird integration and operates on a single phase. Modified Modulation method is suggested based on conventional pulse width modulation (PWM), and the five-level inverter design has been traditionally established for single-phase systems. In this study, MATLAB simulation to examine the performance of the suggested improved PWM with respect to harmonic distortion, leakage current, voltage linearity, output current ripples, and dc-link current ripples. The suggested architecture successfully lowers the leakage current without negatively impacting the system's overall performance.
Because of its large leakage current, conventional pulse width modulation is unsuitable for grid-connected PV systems that do not use transformers. Various modulation approaches and conversion structures have been suggested in [6]-[8] as a means to decrease the leakage current to satisfy the standard's requirement. Constant voltage across the stray capacitance results in zero leakage current in [9] because the neutral of the grid is connected to the centre point of the dc-link. Unfortunately, the inductance in the neutral line is created by such a connection, therefore it is not practicable. A leakage current greater than the standardrecommended acceptable amount is caused by this inductance, which creates a high-frequency potential between the PV array and the ground [10].
Key Words: Multilevel inverter, Solar PV system, Grid connected system, Leakage current, renewable energy sources
1.INTRODUCTION Researchers are now focusing on photovoltaic (PV) energy as a solution to the problems caused by the everincreasing demands of modern society. PV energy is renewable, sustainable, and never-ending [1]. As a result of technological advancements in power electronics and semiconductors, as well as government incentives and falling PV array costs, PV power systems have recently become ubiquitous.
The five-level topology has traditionally been designed for single-phase systems, hence in order to adapt it to singlephase systems, a matching single-phase modulation approach needs to be devised. This article so proposes a modified PWM that is based on the regular PWM. In terms of leakage current, dc-link current ripples, output current ripples, and the THD of the output current, the performance of the converter topology with the suggested modulation approaches is compared to other known PWM methods [11][13]. Discussions revolve on simulations conducted in Matlab/Simulink. For 230V (rms) grid systems, it has been shown that a five-level inverter structure coupled with the suggested modulation approaches provides the optimal overall performance for transformer less PV applications.
There are two main varieties of electricity systems that are linked to the grid: those with and without transformers. On the alternating current side, the transformer might be a low-frequency model, or a high-frequency one [2]. In addition to increasing the input voltage, it prevents dc current injection into the grid and removes leakage current by galvanic isolation, which is a crucial safety feature. The transformers are costly, cumbersome, and hefty, however. Consequently, these problems are addressed by introducing transformer less PV systems. In addition to being more efficient, they are less expensive, lighter, and smaller [3].
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The structure of this paper is as follows: Section II presents the five-level inverter conversion structure with suggested modulation approaches. section III presents the suggested modulation methods and the operating principles. Section IV displays the simulation results that verify the
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