Penetration Of Photovoltaic Systems Research Articles

Modelling and Analysis of High Performance for Solar Power Injection with Distribution Networks

Given the growing emphasis on environmental consciousness, there is a spike in the integration of solar photovoltaic energy into contemporary distribution networks. Interestingly, there is a non-linear relationship between the energy production of solar modules and changing external environmental conditions. In response, this study aims to increase the effectiveness of solar photovoltaic systems (SPVS) by putting out a careful analysis to ascertain the ideal performance criteria for the integration of renewable energy sources into distribution networks. The use of a Maximum Power Point Tracker is crucial to this assessment (MPPT). The model provides important insights into the possible increases in energy efficiency, making it a strong tool in this optimization process. In addition, the research conducts a comparison analysis, examining the distribution system properties in relation to different levels of solar PV system penetration. This aspect of the research illuminates the consequences of harmonic-induced distortions in current and voltage on the feeder networks in the distribution system. The simulation findings clearly show that as the penetration capacity of the PV system increases, so does the amount of harmonic dispersion that is introduced into the network. This suggests that it would be wise to incorporate the photovoltaic (PV) array only as far as the network can support it in order to prevent any possible performance reduction. Using MATLAB/SIMULINK as a computational tool, the research carefully examines the important characteristics from the technical data in order to examine the overall model. Further testing of the model's flexibility and resilience under a range of weather scenarios and partial shade conditions offers a thorough assessment of the model's performance dynamics. Positively, the investigation concluded with results that were satisfactory and confirmed the system's exceptional performance capabilities, which are supported by the MPPT. This result reflects a positive trend toward maximizing the integration of renewable energy sources into distribution networks, which will help to create a more sustainable and environmentally friendly energy landscape.

Optimal Capacity of a Battery Energy Storage System Based on Solar Variability Index to Smooth out Power Fluctuations in PV-Diesel Microgrids

Battery energy storage systems can be integrated with photovoltaic (PV)-diesel microgrids as an enabling technology to increase the penetration of PV systems and aid microgrid stability by smoothing out the power fluctuations of the PV systems. This paper focuses on this topic and aims to derive correlations between the optimal capacity of the smoothing batteries and variabilities in the daily solar irradiance. To this end, the two most commonly used moving average and ramp rate control techniques are employed on a real solar irradiance dataset with a 1-min resolution for a full calendar year across 11 sites in Australia. The paper then presents the developed empirical model, based on linear regressions, to estimate the batteries’ optimal capacity without requiring detailed simulation studies, which are useful for practitioners at the early stages of a project’s feasibility evaluation. The performance of the developed technique is validated through numerical simulation studies in MATLAB®. The study demonstrates that the empirical model provided reasonably accurate estimates when using the moving average smoothing technique but had limited accuracy under the ramp rate control technique.

Aspects to Consider in the Evaluation of Photovoltaic System Projects to Avoid Problems in Power Systems and Electric Motors

This paper analyzes the problems in electrical power systems with high penetration of photovoltaic systems, which must be considered in evaluating new projects with these generation sources. The study analyzes the characteristics of photovoltaic systems, their generated effects, and proposals for technological improvements. The features of electric motors and their affectation when they are fed from networks with power quality problems are also described. As a result, the variability in energy production, the difficulties in frequency regulation, the increase in harmonics, and the instability in generating reactive power, are the main problems caused by the massive use of photovoltaic systems. Regarding electric motors, it is shown that harmonics and voltage regulation are the power quality problems that most affect their operation. None of the studies conducted analyzes the direct influence that photovoltaic systems can have on the process of electric motors. Considering the growth prospects for using photovoltaic systems and the importance of electric motors, it is suggested that the scientific community develop research focused on this problem.

Decarbonizing Telecommunication Sector: Techno-Economic Assessment and Optimization of PV Integration in Base Transceiver Stations in Telecom Sector Spreading across Various Geographically Regions

Renewable energy is considered to be sustainable solution to the energy crisis and climate change. The transition to renewable energy needs to be considered on a sectoral basis and one such sector that can potentially decarbonized with renewable energy is the telecommunication sector. Several base transceiver stations (BTS) in remote regions have unstable electric supply systems. Diesel generators (DG) are a common solution to energy problems on such telecommunication sites. However, they have high fuel costs on the global market and contribute to high carbon emissions. Hybrid renewable energy systems may provide a stable power output by integrating multiple energy sources, essential for supplying a dependable and uninterrupted power supply in the context of the telecom sector, notably base transceiver stations (BTS). Deploying such a system might also help BTS, which relies mainly on diesel generators with battery storage backup, reduce operational costs and environmental problems. This study presents the framework for large-scale photovoltaic system penetration based on techno-economic analysis (based on actual on ground data with least assumptions) in base transceiver stations (BTS) encapsulating telecom sector spread across various geographical regions. The proposed framework includes a mathematical model complemented with system design in HOMER software tool. The techno-economic aspects of the study were spread across 2, 12 and 263 sites, along with comparison analysis of photovoltaic system installation with and without energy storage devices, respectively. The sites included both on-grid and off-grid sites, which were exposed to high levels of power outages and subjected to reliance on costly and environmentally hazardous diesel generators. Optimization results showed that the photovoltaic system with a diesel generator and battery storage system provide a promising solution to the energy problem, with an average decrease in LCOE of 29%, DG hour’s reduction by 82% with 92% reduction in carbon emission and a reduction in NPC of 34% due to the high availability of solar. The techno-economic analysis indicated that optimized photovoltaic system and storage results in both on–off grid BTS sites with better options, amid low cost of energy and free accessibility of solar. Moreover, the results spread across geographical regions aiming at a reliable and environmentally friendly option that reduces load on utility grid across on-grid BTS sites and substantial overall reduction in diesel usage.

Evaluation of the Spanish regulation on self-consumption photovoltaic installations. A case study based on a rural municipality in Spain

In European countries, an energy transition towards renewable energies is taking place, promoting self-consumption photovoltaic systems. Some studies point out that the existing regulations and support for photovoltaic systems is still scarce in Spain. This work analyses the penetration of photovoltaic systems and their amortisation in rural areas within the Spanish regulatory framework. For this purpose, an economic decision-making method for the implementation of photovoltaic systems is proposed. This method is based on comparing the possible self-consumption scenarios included in the Spanish regulation and their payback periods. Subsequently, a rural municipality in Spain has been analysed in detail as a case study. Results show that the Spanish regulation on self-consumption does not provide an adequate profitability in rural areas, as the amortisation period with surplus sale is between 16 and 22 years. If the surplus generation is not sold, the payback rises up to 28 years. Therefore, from the economical point of view, photovoltaic generation power plants with surplus sale are more attractive than self-consumption installations, as the payback period is around 12 years. Consequently, a change in the current Spanish regulations is necessary to support individual self-consumption photovoltaic installations, to make them as profitable as photovoltaic generation power plants.

Evaluation of Grid-Connected Photovoltaic Plants Based on Clustering Methods

Photovoltaic (PV) systems are electric power systems designed to supply usable solar power by means of photovoltaics, which is the conversion of light into electricity using semiconducting materials. PV systems have gained much attention and are a very attractive energy resource nowadays. The substantial advantage of PV systems is the usage of the most abundant and free energy from the sun. PV systems play an important role in reducing feeder losses, improving voltage profiles and providing ancillary services to local loads. However, large PV grid-connected systems may have a destructive impact on the stability of the electric grid. This is due to the fluctuations of the output AC power generated from the PV systems according to the variations in the solar energy levels. Thus, the electrical distribution system with high penetration of PV systems is subject to performance degradation and instabilities. For that, this project attempts to enhance the integration process of PV systems into electrical grids by analyzing the impact of installing grid-connected PV plants. To accomplish this, an indicative representation of solar irradiation datasets is used for planning and power flow studies of the electric network prior to PV systems installation. Those datasets contain lengthy historical observations of solar energy data, that requires extensive analysis and simulations. To overcome that the lengthy historical datasets are reduced and clustered while preserving the original data characteristics. The resultant clusters can be utilized in the planning stage and simulation studies. Accordingly, studies related to PV systems integration into the electric grid are conducted in an efficient manner, avoiding computing resources and processing times with easier and practical implementation.

Comparative Analysis of Power Distribution Systems with Individual Prosumers Owing Photovoltaic Installations and Solar Energy Communities in Terms of Profitability and Hosting Capacity

Future energy markets are foreseen to integrate multiple entities located mainly at the distribution level of the grid so that consumers can participate in energy trading while acting as individual prosumers or by forming energy communities. To ensure the smooth integration of prosumers and satisfy the effective operation of the power distribution systems (PDSs), it is important to fundamentally assess their performance for different grid development scenarios. This paper aims to estimate and compare the hosting capacity (HC) thresholds and profitability for two alternatives: (a) when the PDS experiences rapid growth of scattered individual prosumers with photovoltaic (PV) installations and (b) when prosumers intend to formulate a medium-scale energy community, which is a single source located in one node. Maximization of the profits of decision-makers and maximization of the capacity of the PV generation were set as the two objectives for the optimization tasks. It has been analyzed how the physical topology of the distribution network can be harmonized with the underlying bidirectional power flows for each alternative while satisfying system constraints. A typical distribution test feeder is employed to estimate the energy loss and voltage variations in the PDS, as well as the profitability for energy producers, for various penetration levels of prosumers, in comparison to the base case with no PV generation. The results indicate that improvements in terms of profitability and reduction of energy losses can be achieved in both alternatives, as long as the penetration of PV systems does not reach a certain threshold, which can be chosen by decision-makers and is limited by the HC. Comparing the results of the simulation, EComs demonstrate higher HC vs. individual prosumers, both in terms of technical and economic priorities.

DC Optimal Power Flow Model to Assess the Irradiance Effect on the Sizing and Profitability of the PV-Battery System

The decreasing cost of renewable energy resources and the developments in storage system technologies over recent years have increased the penetration of photovoltaic systems to face the high rise in the electricity load. Likewise, there has also been an increase in the demand for tools that make this integration process in the current power systems profitable. This paper proposes a mathematical model based on the DC optimal power flow equations to find the optimal capacity of the PV panels and batteries for a standalone system or a system supported by the grid, while the investment and the energy required by the grid are minimized. In this regard, five different locations have been used as case studies to measure the influence of the irradiance level on the PV-Battery capacity installed and on the economic indicators such as CAPEX, OPEX, NPV, IRR, and the payback period. Thus, a modified 14-bus system has been used to replicate the grid technical limitations and show that a PV-Battery system connected to the grid could produce 26.9% more savings than a standalone PV-Battery and that a location with irradiance levels over 6.08 (kWh/m2/yr) could reduce the payback period for two years.

An advanced protection scheme for medium-voltage distribution networks containing low-voltage microgrids with high penetration of photovoltaic systems

This article aimed at the development of an advanced adaptive protection scheme that can provide protection for both medium-voltage distribution networks and their included low-voltage microgrids with high penetration of photovoltaic systems in a thorough manner. On the one hand, the scheme can address those issues related to the protection coordination between medium-voltage and low-voltage protection systems while still be able to prevent the low-voltage microgrids from unwanted tripping for disturbances on adjacent medium-voltage feeders. Moreover, the safe operation of low-voltage microgrids in different operation modes as well as their reliable transition between these modes can be guaranteed. On the other hand, this scheme can enable the connected photovoltaic systems at both medium-voltage and low-voltage networks not only to meet the fault ride through but also fault dynamic voltage support requirement imposed by new grid codes. The developed scheme was validated on a real medium-voltage network consisting of various low-voltage microgrids by simulating in the software environment DIgSILENT/PowerFactory. The transient models of photovoltaic and battery energy storage system were considered in detail with regards to the new grid code requirements in order to achieve a higher degree of realism of the simulated networks.

Impact of Grid Voltage and Grid-Supporting Functions on Efficiency of Single-Phase Photovoltaic Inverters

High penetrations of rooftop photovoltaic (PV) systems are creating several challenges for distribution network operators, most critically overvoltage during periods of peak solar generation. To assist with voltage regulation across distribution networks, grid-supporting functions, such as Volt–Watt ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$P(V)$</tex-math></inline-formula> ) and Volt–VAr ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$Q(V)$</tex-math></inline-formula> ) response modes, are now part of many grid connection standards for PV inverters. The constantly varying voltage profile during daylight hours, particularly in networks with high penetrations of PV systems, requires an inverter operation to vary from nonunity power factor with connection voltages that depart from their nominal values. However, current discussions on PV inverter efficiency focus on calculations and measurements under a unity-power-factor operation while assuming nominal voltage conditions. This article measures and analyzes the efficiency of commercial PV inverters across a more comprehensive and realistic range of voltage and power factors. The impact of grid-supporting modes on PV inverter efficiency is also evaluated experimentally. The definitions of the European and California Energy Commission efficiencies are expanded from a single value to an efficiency curve accounting for the impact of the grid voltage and the power factor. A <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">voltage-weighted PV inverter efficiency</i> metric is proposed that collectively considers the combined impact of solar irradiance, grid-supporting functions, and grid voltages. Experimental measurements from eight commercial PV inverters demonstrate that PV inverters under abnormal grid voltage conditions and with grid-supporting functionalities show lower efficiency values.

Coordinated active and reactive power control for distribution networks with high penetrations of photovoltaic systems

A primary concern of the large-scale application of photovoltaic (PV) power systems in distribution networks is nodal voltage fluctuations caused by active power fluctuations of PV. Therefore, this paper proposes a novel coordinated active and reactive power optimization method for distribution networks with high penetrations of PV systems, which can reduce bus voltage fluctuations, active power curtailments of PV, operating losses of distribution networks, and adjustments of conventional voltage regulation devices such as on-load tap changers (OLTCs) and capacitor banks (CBs). The proposed method coordinates the OLTC, CBs, and PV and BESS plants in two levels. The upper level establishes a mixed integer nonlinear programming (MINP) model based on the model predictive control (MPC), which can properly plan the operation of the OLTC, CBs, and PV, and a modified NSGA-II algorithm is developed to find the best solution of the MINP model. The lower level employs the leader–follower consensus algorithm (LFCA) to coordinate the charging power and reactive power of distributed battery energy storage systems (BESSs) to control real-time bus voltage fluctuations. The LFCA based control method can make BESSs fairly participate in the real-time voltage regulation of each feeder. Case studies are conducted on a modified IEEE 33-bus distribution network system, utilizing the actual active power data of a PV plant. Simulation results indicate that the proposed method can effectively control bus voltage variations of all feeders within the pre-defined range, and the distribution network can operate with higher penetrations of PV power systems, lower losses, and better economy.

Resource management with kernel-based approaches for grid-connected solar photovoltaic systems

The increasing penetration of photovoltaic (PV) power generation into the distribution grids has resulted in frequent reverse active power flows, rapid fluctuations in voltage magnitudes, and power loss. To overcome these challenges, this paper identifies the resource management of grid-connected PV systems with active and reactive power injection capabilities using smart inverters. This approach is aimed to minimize the voltage deviations and power losses in the grid-connected systems to accommodate the high penetration of PV systems. A kernel-based approach is proposed to learn policies and evaluate the reactive power injections with smart inverters for improving grid profile, minimizing power losses, and maintaining safe operating voltage limits. The proposed approach performs inverter coordination through nonlinear control policies using anticipated scenarios for load and generation. To assess the performance of the proposed approach, numerical simulations are performed with a single-phase grid-connected PV system connected to an IEEE bus system. The results show the effectiveness of the proposed approach in minimizing power losses and achieving a good voltage regulation.

Proposal of Priority Schemes for Controlling Electric Vehicle Charging and Discharging in a Workplace Power System with High Penetration of Photovoltaic Systems

Using Electric Vehicles (EV) as Flexible Resources (FR) to increase surplus Photovoltaic (PV) power utilisation is a well-researched topic. Our previous study showed that EVs are viable as supplementary FRs in large capacity PV power systems, where EVs are likely to gather (i.e., workplaces). However, that study assumed all EVs to have identical arrival and departure times (availability), and battery capacities. As these characteristics may vary between EVs and affect their performance as FRs, this study expands the modelling of EVs to consider a variety of availabilities and battery capacities. To effectively utilise a variety of EVs as FRs, an Optimisation Electric-load Dispatching model is used to formulate priority schemes for charging and discharging the EVs based on their potential to contribute to the power system. The priority schemes are evaluated by simulating the annual operation of the power system both with and without the priority schemes, and comparing results. The power system is simulated using a Unit-Scheduling and Time-series Electric-load Dispatching model. The priority schemes reduced annual CO2 emissions by nearly 1%, compared to the case without the priority schemes. The performances of different EVs as FRs when the priority schemes are used and not used are also analysed.

Central Energy Storage System to Reduce the Harmful Effects of PV Systems under a High Penetration Scenario

Photovoltaic (PV) systems are used to generate electricity and they are considered less aggressive in their environmental impact. These systems require no further maintenance once they are installed, they do not pollute the environment and their average lifespan is high. These are the reasons why they are considered a good alternative for electricity generation. However, PV systems have different challenges to solve when they are connected to low voltage distribution grids and one of them is related to the power quality when there is a high penetration of PV systems, when voltage variations usually appear. In this paper, a central energy storage system (ESS) is considered to alleviate grid voltage variations under a high penetration scenario of PV systems instead of using multiples ESS. The proposal controls the energy injected into the grid to maintain the voltage variation within the standard, no limitations are imposed on the PV systems, and then as an advantage of the proposal, the PVs’ available energy is fully delivered to the grid. In addition, in the absence of sunlight the ESS may provide power to the grid. An analysis and experimental setup were built to validate the proposed scheme.

Primary frequency control of large-scale PV-connected multi-machine power system using battery energy storage system

&lt;span lang="EN-US"&gt;Large-scale grid-tied photovoltaic (PV) station are increasing rapidly. However, this large penetration of PV system creates frequency fluctuation in the grid due to the intermittency of solar irradiance. Therefore, in this paper, a robust droop control mechanism of the battery energy storage system (BESS) is developed in order to damp the frequency fluctuation of the multi-machine grid system due to variable active power injected from the PV panel. The proposed droop control strategy incorporates frequency error signal and dead-band for effective minimization of frequency fluctuation. The BESS system is used to consume/inject an effective amount of active power based upon the frequency oscillation of the grid system. The simulation analysis is carried out using PSCAD/EMTDC software to prove the effectiveness of the proposed droop control-based BESS system. The simulation result implies that the proposed scheme can efficiently curtail the frequency oscillation. &lt;/span&gt;

Risk Assessment of Power Systems Dispatching Decision Considering Photovoltaic Systems Penetration

Grid-connected photovoltaic power generation is an important form of new energy utilization, which can effectively reduce the dependence of power system on traditional energy sources. However, the randomness and uncertainty of the output of photovoltaic power generation system will also pose some risks to power grid dispatching decision-making. The source of dispatching decision risk is analyzed, and a risk index system including line overload risk, reserve shortage risk, load shedding risk and light abandonment risk is established. Then a risk assessment model for optimal dispatch of grid-connected photovoltaic power generation is established. The time of power flow calculation is greatly simplified by using power flow distribution factor. Finally, through the risk assessment of IEEE RTS-79 system scheduling decision-making, the risk of scheduling decision-making under different photovoltaic acceptance is analyzed, and the feasibility of the model is verified.

Harmonic Effects Due to the High Penetration of Photovoltaic Generation into a Distribution System

The growth in global electricity demand has expanded the search for new energy resources. Renewable sources such as photovoltaic (PV) systems have proven to be major alternatives. PV generators connected to distribution grids have exhibited significant growth in the last decade, so it is essential to analyse the impacts resulting from this increase. This work investigated the influence of high PV system penetration in distribution grids in terms of harmonic levels. In particular, this study addressed the distortions in voltage and current waveforms in the presence and absence of PV generators connected to a distribution grid. Additionally, the total harmonic content and the individual harmonic frequencies of voltage and current were analysed. This study was performed with an IEEE 37 bus distribution system and the Open Distribution System Simulator software (OpenDSS). The results show that the voltage limits of some phases far away from a substation can exceed the limits. Furthermore, the total harmonic distortion (THD) and individual harmonic distortion (IHD) levels for voltage and current were significantly high for harmonics of the 3rd, 5th, and 7th orders, where current levels violate the standard levels.

Comparative analysis of methods for cloud segmentation in ground-based infrared images

The increasing penetration of photovoltaic systems in the power grid makes it vulnerable to cloud shadow projection. Real-time cloud segmentation in ground-based infrared images is important to reduce the noise in intra-hour global solar irradiance forecasting. We present a comparison between discriminative and generative models for cloud segmentation. The performances of supervised and unsupervised learning methods in cloud segmentation are evaluated. The discriminative models are solved in the primal formulation to make them feasible in real-time applications. The performances are compared using the j-statistic. Infrared image preprocessing to remove stationary artifacts increases the overall performance in the analyzed methods. The inclusion of features from neighboring pixels in the feature vectors leads to a performance improvement in some of the cases. Markov Random Fields achieve the best performance in both unsupervised and supervised generative models. Discriminative models solved in the primal yield a dramatically lower computing time along with high performance in the segmentation. Generative and discriminative models are comparable when preprocessing is applied to the infrared images.

State coordinated voltage control in an active distribution network with on-load tap changers and photovoltaic systems

Decreasing costs and favorable policies have resulted in increased penetration of solar photovoltaic (PV) power generation in distribution networks. As the PV systems penetration is likely to increase in the future, utilizing the reactive power capability of PV inverters to mitigate voltage deviations is being promoted. In recent years, droop control of inverter- based distributed energy resources has emerged as an essential tool for use in this study. The participation of PV systems in voltage regulation and its coordination with existing controllers, such as on-load tap changers, is paramount for controlling the voltage within specified limits. In this work, control strategies are presented that can be coordinated with the existing controls in a distributed manner. The effectiveness of the proposed method was demonstrated through simulation results on a distribution system.

Aggregator units allocation in low voltage distribution networks with penetration of photovoltaic systems

The aggregator units are essential in implementing smart grids since they are responsible for connecting smart meters installed on the consumers and ensuring exchanging information with the utility control centers. This paper presents a methodology to allocate these aggregators in low voltage distribution systems with solar photovoltaic generation. The proposed method is composed of two stages. In the first one, the aggregators are allocated considering the minimization of the distance to the remote terminal unit and their installation costs using a method based on Particle Swarm Optimization. In the second stage, the smart meters are connected to each allocated aggregator using a graph method. These connections are performed, taking into account a function, which depends on the distance between the meters and the load density within the aggregator coverage area. The proposed methodology was tested using a 400 V low voltage distribution system with 45 residential loads and 12 photovoltaic generators. The results showed that the proposal allocates aggregators at points where the consumer groups' load curves into the aggregator coverage area are better characterized. The values of the average voltage profile and the system's power losses in each aggregator coverage area presented an excellent match with values obtained with the test system without installing aggregators. From this characterization, it is possible to get useful information for operational planning and expansion planning of low voltage networks with photovoltaic generators by aggregation areas.