A Unified Power-Setpoint Tracking Algorithm for Utility-Scale PV Systems with Power Reserves and Fast Frequency Response Capabilities

TL;DR

This paper introduces a rapid and accurate power-setpoint tracking algorithm for utility-scale PV systems, combining MPPE and FPPT to enhance grid services like reserves and frequency response under changing solar conditions.

Contribution

A novel unified algorithm that integrates MPPE with adaptive FPPT for improved PV power tracking speed and accuracy, especially during irradiance fluctuations.

Findings

Achieves fast convergence within three FPPT iterations.

Effectively decouples irradiance effects from power measurements.

Outperforms existing methods in testbed experiments.

Abstract

This paper presents a fast power-setpoint tracking algorithm to enable utility-scale photovoltaic (PV) systems to provide high quality grid services such as power reserves and fast frequency response. The algorithm unites maximum power-point estimation (MPPE) with flexible power-point tracking (FPPT) control to improve the performance of both algorithms, achieving fast and accurate PV power-setpoint tracking even under rapid solar irradiance changes. The MPPE is developed using a real-time, nonlinear curve-fitting approach based on the Levenberg-Marquardt algorithm. A modified adaptive FPPT based on the Perturb and Observe technique is developed for the power-setpoint tracking. By using MPPE to decouple the impact of irradiance changes on the measured PV output power, we develop a fast convergence technique for tracking power-reference changes within three FPPT iterations. Furthermore, to limit the maximum output power ripple, a new design is introduced for the steady-state voltage step size of the adaptive FPPT. The proposed algorithm is implemented on a testbed consisting of a 500 kVA three-phase, single-stage, utility-scale PV system on the OPAL-RT eMEGASIM platform. Results show that the proposed method outperforms the state-of-the-art.