Photovoltaic System Control for Power System Frequency Support in Case of Cascading Events

In a power system with a high-share of photovoltaic systems, the frequency response can be improved by the participation of photovoltaics in frequency control. If the photovoltaic system operates at reduced power, in a so-called de-loaded mode, and maintains a specific amount of power reserve, then participation in system frequency control is usually realized by a droop control method. The implementation of this method is very simple, but it does not provide the recovery of PV power reserve before the secondary frequency control reacts. This means the PV system cannot provide additional support to the grid if a new disturbance occurs in a short time following the first one. This paper presents a novel approach for PV system control in providing support to system frequency. The novel control algorithm aims to enable rapid recovery of PV power reserve which makes the PV system capable of providing support to the cascading disturbance events. The development of such PV system control model is based on a detailed mathematical analysis of the dynamic frequency response. The effectiveness of the proposed method was tested on a two-area multi-machine power system model and through 4 different study cases.