The installed capacity of photovoltaic (PV) systems has recently increased at a much faster rate than the development of grid codes to effectively and efficiently manage high penetrations of PV within the distribution system. In a number of countries, PV penetrations in some regions are now raising growing concerns regarding integration. Management strategies vary considerably by country-some still have an approach that PV systems should behave as passive as possible, whereas others demand an active participation in grid control. This variety of grid codes also causes challenges in learning from "best practice." This paper provides a review of current grid codes in some countries with high PV penetrations. In addition, the paper presents a number of country-specific case studies on different approaches for improved integration of PV systems in the distribution grid. In particular, we consider integration approaches using active and reactive power control that can reduce or defer expensive grid reinforcement while supporting higher PV penetrations
The recovery time of a transformer type SC-FCL (Superconducting Fault Current Limiter) with adjustable trigger current level, is studied experimentally. The recovery time is defined as the required time of zero current period of SCFCL for recovery from its current limiting mode to its waiting mode. A trial SCFCL, which was designed and made, is tested to measure the recovery time with various fault time. The experimental results show that the recovery time depends on the fault time. When the fault time is longer than 200 ms, the recovery time becomes shorter and approaches a certain value (a few ten ms) as the fault time is longer.
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