Hybrid Wind–PV Frequency Control Strategy under Variable Weather Conditions in Isolated Power Systems

Ana Fernández-Guillamón,Jose-Ignacio Sarasua,Ángel Molina-García,Guillermo Martínez-Lucas

doi:10.3390/su12187750

Ana Fernández-Guillamón, Jose-Ignacio Sarasua + Show 2 more

Open Access

https://doi.org/10.3390/su12187750

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Abstract

Over the last two decades, variable renewable energy technologies (i.e., variable-speed wind turbines (VSWTs) and photovoltaic (PV) power plants) have gradually replaced conventional generation units. However, these renewable generators are connected to the grid through power converters decoupled from the grid and do not provide any rotational inertia, subsequently decreasing the overall power system’s inertia. Moreover, the variable and stochastic nature of wind speed and solar irradiation may lead to large frequency deviations, especially in isolated power systems. This paper proposes a hybrid wind–PV frequency control strategy for isolated power systems with high renewable energy source integration under variable weather conditions. A new PV controller monitoring the VSWTs’ rotational speed deviation is presented in order to modify the PV-generated power accordingly and improve the rotational speed deviations of VSWTs. The power systems modeled include thermal, hydro-power, VSWT, and PV power plants, with generation mixes in line with future European scenarios. The hybrid wind–PV strategy is compared to three other frequency strategies already presented in the specific literature, and gets better results in terms of frequency deviation (reducing the mean squared error between 20% and 95%). Additionally, the rotational speed deviation of VSWTs is also reduced with the proposed approach, providing the same mean squared error as the case in which VSWTs do not participate in frequency control. However, this hybrid strategy requires up to a 30% reduction in the PV-generated energy. Extensive detailing of results and discussion can be also found in the paper.

Highlights

Over the last two decades, power systems’ generation has slowly been changing, replacing conventional generation units with variable renewable energy sources [1]
Frequency control is provided by conventional power plants and wind power plants (WPPs) with a hidden-inertia emulation technique
Frequency control is provided by conventional power plants, WPPs with a hidden-inertia emulation technique, and PV power plants with 10% de-loading and a PI controller with ∆ω of the variable-speed wind turbines (VSWTs) as input (referred to as PV (ω)), which is the hybrid wind–PV frequency strategy proposed in this paper

Summary

Introduction

Over the last two decades, power systems’ generation has slowly been changing, replacing conventional generation units (mainly based on the fossil and nuclear fuels) with variable renewable energy sources (vRESs) [1] This transition has been supported by several aspects, including environmental concern (especially greenhouse gas emissions) and the aim of decreasing the energy dependence of third countries [2,3,4]. As an attempt to improve the frequency response of power systems with high vRES integration, several frequency control techniques have been proposed for such generation units in the specific literature [11,12] With regard to PV power plants, as they are static elements without any rotating parts, they do not have any stored kinetic energy [15]

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