Experimental Indicators of Current Unbalance in Building-Integrated Photovoltaic Systems

Abstract

Unbalance of the three-phase currents in photovoltaic (PV) systems may depend on structural aspects of the installation, the effect of partial shading, or both. In this paper, a number of unbalance indicators are calculated starting from data that are measured during experimental analyses on a real building-integrated PV system that represents different types of unbalance. Detailed information is obtained from indices that identify the balance and unbalance components that are also in the presence of waveform distortion. These indices extend the current definitions of unbalance given in the power quality standards. The results show that the unbalance cannot be considered negligible, even with no singlephase inverters and is more significant if nonlinear loads add a contribution to both harmonic distortion and unbalance seen from the distribution transformer.

Impact of Rooftop Photovoltaics on the Distribution System

“…e opposite is true when the sky shows transitions from cloudy to sunny conditions. e authors have explained this phenomenon by associating it with ambient temperature, i.e., as the sky shows transitions [59, 74-76, 78, 81, 84, 86-88, 94, 96, 99, 100, 107, 109, 110, 122, 123, 128, 129, 153, 155, 168, 171, 174, 176, 183, 187, 188, 200, 213, 214, 230, 235] Effect of system strength (R/X ratio) [155,177,234] Impact of PV on voltage swell/sag [145,169,170,194,211] Effects of cloud movements, cloud pattern, or shading [19,27,59,61,64,67,75,86,96,99,100,107,109,131,146,160,178,215,218,224,240,242,243,258] from sunny to cloudy, both solar irradiance and temperature decrease. A decrease in irradiance decreases the output power of PVs, but temperature drop has an inverse effect.…”

100 Years of Symmetrical Components

“…The independent control of positive and negative voltage sequences in the compensation of unbalanced voltages by means of a static synchronous compensator (STATCOM) has been proposed in [84]. Different types of unbalance (structural, from partial shading, and mixed) have been characterised in [85] for photovoltaic (PV) systems operated with distorted waveforms by using the SCB approach. The control strategies used to inject the generated active power of a PV system into the grid, while providing also reactive power according with the grid code, have to be set up to operate in balanced and unbalanced conditions.…”

A power and energy procedure in operating photovoltaic systems to quantify the losses according to the causes

“…This energy prediction is compared with the monitored value E AC_m (affected by uncertainty, typically of ±1%) by the relative deviation  p-m according to (2). it is very hard to achieve a tolerance of maximum power lower than ±3% and the deviations in current and voltage at MPP are still greater with a consequent higher potential of mismatch.…”

“…Hence, it is important to evaluate the losses in the energy production according to the different causes. The Building Integrated PhotoVoltaic (BIPV) systems are affected by a number of worsening phenomena [2] such as: shading effects generated by near obstacles; thermal gradients from lower parts to upper parts of the roofs; impact of dirt for pollution; nonoptimal exposition to the Sun. But the most of photovoltaic capacity is composed of large PV systems mounted at ground level.…”