I. Introduction
In recent years, the world-wide capacity of renewable energy systems has grown rapidly in order to relieve the deteriorating environmental issues generated by fossil fuels. Among numerous renewable energy sources, solar energy is one of the most promising resources for large-scale electricity production [1]. However, the key barrier against high PV penetration is the power output variability, which is mainly caused by cloud shading [2]–[4]. In the case of a large grid-connected PV system, passing clouds can result in fluctuating power being continuously injected into the power grid, leading to large power ramp-rates [5]. The uncontrolled PV penetration may change the dispatch of utility regulating, and thus cause a violation in dispatch regulating margins [6]. In small power systems such as islands, the intermittent PV power can cause harmonic distortion in current and voltage waveforms and even blackouts [7]. As a result, PRRC is introduced as the regulation of PV output power change rate. For instance, Germany and Puerto Rico require a maximum ramp-rate of 10% per minute of the rated PV power [8].