Assessment of Roof-Top Photovoltaic Installations on the Total Harmonic Distortion of Low Voltage Distribution Networks

The connections of roof-top photovoltaic (PV) systems with low voltage distribution networks have been raised dramatically in the last years due to decreasing in the capital cost and investing in the operating cost. However, the power generation of this source is variable owing to the solar irradiance dependency. This variation in the PV generation can cause a Total Harmonic Distortion (THD) into the low voltage distribution network. In this paper, the effect of roof-top PV system installations on the total harmonic distortion is assessed under different weather conditions. Regarding this, the voltage and current of an on-grid PV system composited at the roof-top of Brunel university London campus are measured and analysed for sunny and cloudy days. Furthermore, this installed PV system is developed based on MATLAB/Simulink. The results prove that the solar irradiance of the surround PV system has a significant impact on the THD-current when compared with the THD-voltage.

I. Introduction

Recently, the global installations of photovoltaic (PV) sources have been increased dramatically. This is because that several countries have connected large PV plants with a grid such as China and India. Moreover, other countries have encouraged their citizens to install PV systems on the roof-top of their houses such as USA and UK. By the end of 2019, the global installations of PV systems exceeded 600 GW of which 72% in last five years [1]. However, the variable and light power production of the PV system is considered one of the biggest impact on the performance of a power distribution network when it is connected with utilize grid, because its electrical generation totally depends on the weather conditions [2]. This causes distortion in the output generation of PV system which knowns as a Harmonic Distortion. Although there are several measurements for this issue, the Total Harmonic Distortion (THD) is common considered, which is clarified as the percentage-ratio of the root sum-square of the order harmonic value to its primary value [3].