Power quality concerns and mitigation solutions in respect to smart grid evolution

In a power system network, voltage dip is regarded as the most common power quality (PQ) issue. In general, the causes of voltage dips are mainly due to uncontrollable factors such as lightning, third party interference and system faults. Nowadays, more and more utilities are upgrading their grids to become smarter with smart automation and self-healing features. While supply reliability is undoubtedly uplifted, the concern on PQ issue would be inevitably increased to sensitive customer loads. Although most of these loads have been designed to operate properly under power interruption, they may overlook the extent of their immunity against voltage dips, and therefore the operation become interrupted. This PQ issue not only found in low-power control devices, but also increasingly affected the high-power production lines which nowadays have been heavily integrated with computerized controls. Voltage dip mitigation solutions for small-rating or high-power equipment are different. Usually, small-rating equipment could simply be protected by a 1-phase uninterruptible power supply (UPS) at the control side as a low-cost solution. However, a 3-phase high-power equipment needs to employ a high-power UPS for protecting the whole system from interference under voltage dips. To select a suitable 3-phase high-power UPS, flywheel, battery type or battery-less type UPS could be one of the choices. When adopting 3-phase high-power supercapacitor UPS as the voltage dip mitigation solution, its size, voltage dip correction time and maintenance costs are the major factors needed to be considered. In this paper, not just the experience on application of high-power super-capacitor UPS as voltage dip mitigation solution are shared, but also its performance among other types of high-power solutions including battery-type UPS, flywheel and