Proposing Wavelet-Based Low-Pass Filter and Input Filter to Improve Transient Response of Grid-Connected Photovoltaic Systems

Bijan Rahmani,Weixing Li

doi:10.3390/en9080653

Abstract

Available photovoltaic (PV) systems show a prolonged transient response, when integrated into the power grid via active filters. On one hand, the conventional low-pass filter, employed within the integrated PV system, works with a large delay, particularly in the presence of system’s low-order harmonics. On the other hand, the switching of the DC (direct current)–DC converters within PV units also prolongs the transient response of an integrated system, injecting harmonics and distortion through the PV-end current. This paper initially develops a wavelet-based low-pass filter to improve the transient response of the interconnected PV systems to grid lines. Further, a damped input filter is proposed within the PV system to address the raised converter’s switching issue. Finally, Matlab/Simulink simulations validate the effectiveness of the proposed wavelet-based low-pass filter and damped input filter within an integrated PV system.

Highlights

Rapid growth of non-linear loads increases the presence of harmonics in power systems
Active filters are introduced within power systems to address the issue
The wavelet-based low-pass filter is applied to an advanced universal power quality conditioning system (AUPQS) ([2] for the AUPQS active filter)

Summary

Introduction

Rapid growth of non-linear loads increases the presence of harmonics in power systems.These harmonics lead to the false operation of circuit breakers and relays, reduction in transmission system efficiency, malfunction of electronic equipment, and overheating of transformers. When the grid-end current contains low-order harmonics, the conventional second-order low-pass filter is unable to fully separate the positive-sequence component of grid-end active power [5]. This results in the malfunction of employed active filter. The injection of generated PV power to AC grid will be prolonged due to the large delay of the second-order low-pass filter To address these issues, this paper develops a wavelet-based low-pass filter, using the second generation wavelet theory [6,7,8,9,10]. The developed lifting-based wavelet filter is applied to extract the positive sequence of generated

Methods

Findings

Discussion

Conclusion