Power reserve control of solar photovoltaic system for improved frequency response of a stand-alone power system

Abstract

ABSTRACT The growing share of photovoltaic (PV) installations in power systems, with the consequent reduction in system inertia, has necessitated considering PV systems to participate in grid ancillary services such as fast frequency response (FFR). Power reserve control (PRC) of PV systems, to create the required reserve power, needs the PV systems to be operated at a point below the maximum-power point. This paper presents a novel power-command tracking algorithm for PV systems to realize PRC operation. Based on the single-diode model (SDM) and single measurement sample, the proposed PRC algorithm provides a straightforward estimation of the maximum-power point (MPP) quantities without requiring an irradiance sensor. A self-adaptive voltage-tracking method (inner control) is proposed which directly translates a reference power command into an equivalent voltage command for the interfacing DC-DC converter even under changing irradiance levels. Additionally, the strategy unifies the PRC mode and MPP mode into a single control algorithm, allowing an optimal transition between the two modes of operation. The proposed PRC scheme is implemented on a solar-diesel hybrid power system to provide frequency regulation. An appropriate power reference for the inner controller is generated via an optimally-tuned inertial and damping controller (ID-controller) with constraints on the power command. Various aspects of modeling and control are addressed, and simulation experiments are conducted to illustrate the effectiveness of the suggested approach. The results show that, with the proposed PRC, frequency deviation and rate-of-change of frequency (RoCoF) are reduced by 86% and 59%, respectively compared to MPP-mode operation.