Due to environmental concerns, power system generation is shifting from traditional fossil-fuel resources to renewable energy such as wind, solar and geothermal. Some of these technologies are very location specific while others require high upfront costs. Photovoltaic (PV) generation has become the rising star of this pack, thanks to its versatility. It can be implemented with very little upfront costs, e.g., small solar home systems, or large solar power plants can be developed to generate MWs of power. In contrast with wind or tidal generation, PV can be deployed all around the globe, albeit with varying potentials. These merits have made PV the renewable energy technology with highest installed capacity around the globe. However, PV penetration into the grid comes with its drawbacks. The inverter-interfaced nature of the PV systems significantly impacts the power system operation from protection, power flow and stability perspectives. There must be strategies to mitigate these negative impacts so that PV penetration into the grid can continue. This paper gives a thorough overview of such strategies from different research fields: such as communication, artificial intelligence, power electronics and electric vehicle charging coordination. In addition, possible research directions are given for future work.

A Review of Strategies to Increase PV Penetration Level in Smart Grids

More photovoltaics are deployed at distribution networks and these noticeably cause voltage fluctuations in the distribution system. Use of smart inverters (SIs) is investigated as they enhance grid stability with voltage and frequency support. However, these potentially beneficial operating modes of SIs and their impact on the power system operation are not well-known. Conventional simulation packages do not have the tools to run simulations with these inverters. In order to fill this gap and investigate these points, a brand-new simulation platform called Solar Resource Application Platform for Grid Simulation (Sora-Grid) is being developed. In this paper, Sora-Grid's additional capabilities and its unique approach to integrating SIs into the power flow calculations are presented. Some simulation works have been undertaken to show its operation. Furthermore, the results give an insight into understanding the behaviors of SIs and how they impact the distribution grid operation. A typical distribution network with several residential houses is modeled, and the impact of changing operating conditions and active power output on the system voltage is investigated. Finally, a mathematical model is developed to optimize the SI capacity. The optimum point ensures that maximum solar energy is captured, while fair operation is maintained.

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Analysis of Smart Inverter’s Impact on the Distribution Network Operation

Application of sliding mode control for maximum power point tracking of solar photovoltaic systems: A comprehensive review

Penetration of renewable energy based distributed generators into power networks is limited. This is due to several reasons such as intermittency of the generation, low-inertia during disturbances and high variation of local voltage and frequency. Traditionally, distribution networks are designed for a finite voltage drop with distance from feeder connection. When PV panels are deployed at households, their impact on the local voltage profile becomes very substantial. Especially, when there is high solar radiation, generated power increases and the local voltage exceeds the permittable limits. Smart inverters are introduced to tackle this problem. Unlike other inverters, they can follow the local network measurements and provide auxiliary voltage and frequency support. With these features, smart inverters have the ability to push the renewable energy penetration level further. To investigate this phenomenon, custom smart inverter models are developed. Power flow calculation steps are modified to include smart inverter's active inputs. Then, feeder hosting capacity studies were run with conventional and smart inverters to investigate the improvement. Developed models, modified power flow algorithm and results of simulations are reported. Findings show renewable energy share can be increased in networks with smart inverter deployments only, without making substantial changes to rest of the network.

/pdf/impact-of-smart-inverters-on-feeder-hosting-capacity-of-tpt0dp1ucz.pdf

Impact of Smart Inverters on Feeder Hosting Capacity of Distribution Networks

In the most countries around the world, solar photovoltaic power plants have a cost-competitive structure for providing energy access and for increasing electricity production. However, solar photovoltaic power integration requires the handling of power quality and stability problems due to its non-controllable and intermittent characteristics. At this point, the need for reliable solar irradiance and solar power forecasting is emerged for the optimal modeling and scheduling of solar photovoltaic power plants. For this purpose, this study conducts an exhaustive and up-to-date review of solar irradiance and solar power forecasting methods used in the literature. Although there are a plenty of review papers in the literature, differently, we have created the extensive and comparative literature tables considering very-short term, short-term, medium-term and long-term forecasting periods in this study. Furthermore, we have examined each paper in terms of its input data, forecasting interval, forecasting model, forecasting accuracy and forecasting results. As a result of overall assessments, this study provides complete and considerable information about the current status and future prospects in solar irradiance and solar power forecasting.

https://www.ijrer-net.ijrer.org/index.php/ijrer/article/download/7394/pdf

What are the Current Status and Future Prospects in Solar Irradiance and Solar Power Forecasting

In this paper, it is proposed a robust Second-Order Super-Twisting Sliding Mode Control for a Grid-connected inverter of a PV power plant. The proposed control strategy is able to maximize the energy extracted from the PV while regulating the DC-link voltage and achieving a power factor compensation and the reduction of currents harmonic distortion. Both in balanced or unbalanced condition, the grid is supplied by the PV plant with the desired active power and with the developed strategy, it is possible to use the inverter as a reactive power compensator. In order to prove the goodness of the proposed algorithm in terms of high efficiency and performance, some simulated and experimental results are carried out.

Super twisting sliding mode control of smart-inverters grid-connected for PV applications

The paper deals with a Second Order Variable Structure Control (VSC) for Wind Turbine PMSG-based and Generator-side Converter System. By means of the proposed control and the associated sliding observer, a vectorial control of PMSG generator is recognized while maximum power point tracking by the renewable source and DC voltage control of the generator-side converter are assured to maintain a high robustness in the face of parameters and load uncertainties within all the range variations of the controlled quantities.

Second order variable structure control for wind turbine PMSG-based and generator-side converter system

In this article, a current control algorithm is conceived for converting solar dc power into ac power of high-quality. This conversion is based only on a dc-ac converter, avoiding the use of two stage converter. The proposed algorithm is founded on tracking the maximum power point which ensures controlling the electrical power exchanged with the grid. To assure a good dynamics and reduce the control errors, a proportional resonant controllers are utilized and a self-tuning founded on particle swarm optimization is utilized. The proposal strategy goodness is verified by means of numerical simulations.

Di Noia Luigi Pio

Papers

Super twisting sliding mode control of smart-inverters grid-connected for PV applications

Second order variable structure control for wind turbine PMSG-based and generator-side converter system

PSO-PR power flow control of a single-stage grid-connected PV inverter

Design and control of an innovative electronic load for the photovoltaic module characterization