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Rising electricity demand and the need to reduce pollutant emissions highlight the importance of renewable energy, especially solar power. While most studies on photovoltaic (PV) integration focus on developed countries, least developed and developing countries such as the Democratic Republic of Congo (DRC) face particular challenges due to fragile grid infrastructure. This work evaluates the technical and operational impacts of PV integration into the western grid of the DRC using DIgSILENT PowerFactory 2021 SP2 simulations. It examines penetration levels from 10% to 50% based on a 2012 MW baseline, and evaluates power losses, short-circuit ratios (SCRs), grid stability, harmonic distortions, and voltage oscillations. Results reveal that moderate penetration levels (10–20%) reduce active power losses by 25% while maintaining stability. However, above 30% penetration, critical challenges arise, including a drop of the SCR below the minimum recommended value of 3, prolonged voltage oscillations, and increased harmonic distortions, resulting from the reduced overall inertia of the grid following the increase in PV power from inverters without inertia. These findings emphasize the need for targeted solutions like Battery Energy Storage Systems (BESSs), Static Synchronous Compensators (STATCOMs), and harmonic filters. This work provides foundational insights for PV integration in fragile grids of LDCs and developing countries. [ABSTRACT FROM AUTHOR]

Off-grid or grid-connected operation of large-scale photovoltaic system may cause stability problems. When the system performs off-grid operation, energy storage, as balance node, regulates power and frequency, then also influences stability. Under grid-connected operation, the external power system balances power and frequency regulation, and energy storage only equilibrium wave power. Although a detailed model for a single photovoltaic generation system has been established, the connection of numerous photovoltaic units is difficult to model and simulate, and it can easily cause dimension disaster. In order to analyze stability effectively of off-grid/grid-connected operation of large-scale photovoltaic system, we first establish the equivalent model of a photovoltaic farm through the method of dynamic aggregation of wind turbines, and then obtain indicators affecting the stability considering the reactance matrix of the transmission line. When the real part of the oscillation mode sensitivity index is greater than zero, oscillation mode approaches the imaginary axis, indicating that the PV system stability deteriorates. Conversely, the PV system is regionally stable. Finally, the effects of the number of photovoltaic units and transmission line length on stability are theoretically analyzed, and the theoretical derivation is validated through simulations. More PV units and a longer transmission line increase the likelihood of instability through the sensitivity of the oscillation mode.

Achieving the European Union renewable energy source penetration 2030 targets requires an increase in flexible resources to compensate for the variability/intermittency of solar and wind generation to ensure system safety and balancing. Herein, two readily deployable flexibility solutions to balance demand/supply as an alternative to building additional thermoelectric reserves are proposed. How the transmission system OPERATOR can use the ancillary services provided by a flexible photovoltaic (PV) fleet (solar regulation) or PV/wind fleet (variable renewable energy (VRE) regulation) together with a suitable underforecast and proactive curtailment of variable renewable generation (aka, implicit storage) to reduce current and future Italian imbalances is shown. How these flexibility solutions can become even more effective when combined with a strengthening of the transmission grid is shown. The imbalance reduction achievable by 2030 through solar/VRE regulation strategies would be of the order of 20–50% with zonal balancing and 27–80% with nationwide balancing is found. Imbalance costs would remain comparable with the business‐as‐usual (thermal generation) costs. A proactive curtailment of 5–17% of the total VRE generation is the environmental cost of stabilizing the system using VRE plants, avoiding the construction of thermoelectric reserves. [ABSTRACT FROM AUTHOR]

This study examines the problems caused by intermittent renewable energy sources, especially wind farms, and suggests a different solar energy penetration strategy to improve their loading capacity. The study uses real-time data from a wind farm in Jhampir, Pakistan, to analyse and assess various aspects of grid stations connected to wind farms. Electrical Transient Analyzer Program is used to validate the results by linking these with actual grid system. The article focuses on creating a model for a grid connected to a wind farm and the simulation of outcomes following capacity expansion, with the installation of an autotransformer. The original capacity of the wind farm was 750 MW, which was increased to 1,250 MW, i.e., 1.66 times the actual capability. Furthermore, this capacity was further enhanced to 1,540 MW, which becomes 1.23 times the previous capacity by the penetration of a photovoltaic power plant.

Although photovoltaic distributed generation (PVDG) is expanding worldwide, its growth is still relatively small in most countries. Thus, it is necessary to establish appropriate incentive policies that increase the integration of PVDG into the distribution system. The impacts that the adoption of each policy causes must be analyzed to maximize the benefits and minimize the technical problems arising from the integration of PVDG into the grid. In this context, this study proposes a methodology to determine the most appropriate policy to encourage PVDG by observing its technical impacts on the grid. A stochastic model is proposed to determine the technical and financial impacts on voltage levels, technical losses, and peak demand derived from the integration of PVDG. The proposed methodology was applied to dozens of real feeders, seeking to compare the Net Metering (NeM) and the Feed-in Tariff (FiT) policies. The results showed that the NeM policy presented the best performance. Among the two investigated FiT policies, it was verified that the incentive to PVDG with lower powers implies greater benefits. This methodology allows the determination of the most appropriate PVDG incentive policy considering its technical impacts on the grid. • Determination of the most suitable PVDG incentive considering its impacts on the grid. • Determination of technical and financial impacts of PVDG encouraged by public policy. • Stochastic calculation of technical impacts caused by PV distributed generation. • Relation between renewable energy incentive policies and their impacts on the grids. [ABSTRACT FROM AUTHOR]

Using high-resolution grid power balance and market data, this work investigates the effects of rising solar photovoltaic generation on the variability of large-scale net grid load and spot prices, and conducts an analysis of the potential balancing profits of various grid-scale energy storage systems. Analysis results show the correlation between PV (photovoltaic) generation and electricity demand has been identified as a significant factor influencing spot price value. As PV penetration increases, the value of spot prices experiences a notable decline, with values declining to nearly zero when the share of hourly PV generation surpasses 70 %. The volatility of electricity spot prices has a substantial impact on utilization rates and economic profits of energy storage systems employed for grid energy balancing. Despite the lower roundtrip efficiency, reversible hydrogen storage system can offer positive benefits. The longer storage duration offers the advantage of capturing greater dispatch profits by exploiting price differences over extended periods. Considering the time-varying nature of spot prices, the rated power capacity of the storage system plays a significant role in determining its utilization rates. The larger rated charging and discharging ability of the storage system allows for more effective utilization of price fluctuations, resulting in greater profitability. • Impacts of rising PV shares on spot price value and variability of net load are demonstrated. • Analysis results show that rising PV share increases volatility and decreases value of spot price. • Increased volatility of spot prices offers more opportunities to increase storage dispatch profits. • Impacts of storage duration and rated power capacity on dispatch performances are demonstrated. [ABSTRACT FROM AUTHOR]

Large share of solar energy imposes a higher system flexibility to resolve the increased demand/supply imbalance due to the inherent intermittency and variability of the resource. In this work, we demonstrate that the additional solar-induced flexibility requirement can be fully provided by a special kind of solar farms, namely flexible PV. These plants are able to provide ancillary services by proactive generation curtailment and storage power injection and they can be managed exactly as the secondary reserve currently used. At the current and future penetration levels, we sized the flexible PV fleet required to reduce the Italian imbalance by 36 % (with respect to its 2016 value) while keeping the curtailment at 6 % of the national PV generation. We show how this result can be achieved at an equal or lower dispatching cost than current cost (depending on the solar share). In addition, we found that a fleet composed of many flexible PV plants with different capacity randomly distributed throughout the country provides an optimal solar regulation performance. Finally, we showed that the effectiveness of the proposed imbalance mitigation strategy depends only slightly on the year-specific load, wind, PV and energy prices profiles used to size the capacity of the flexible fleet. [ABSTRACT FROM AUTHOR]

The increase in the number of consumers who produce part of their own electricity through photovoltaic distributed generation (PVDG) led to the need for studies on how the power system is affected. As the distribution systems were not designed to integrate PVDG, it is important for regulatory agencies and utilities to identify technical problems in the grid associated with the levels of photovoltaic penetration. In this regard, this study presents a method with indicators that quantify the technical impacts that PVDG growth causes to an actual utility that contains hundreds of feeders with different topologies, load types, and densities. Real solar irradiance and temperature values over a year, and photovoltaic system locations varying based on the Monte Carlo method were also considered in the computational simulations. This study helps the utilities to plan preventive measures to strengthen the grid, and regulatory agencies to enhance policies to support PVDG. We analyzed the impacts on voltage magnitudes, technical losses and peak demand arising from the PVDG integration. The results show that, even at low penetration levels (2%), one-third of feeders required modification in the distribution system to allow photovoltaic integration. For over 60% of feeders, penetration levels of up to 20% reduced technical losses and voltage problems, with practically no effect on peak demand. Feeders in residential and commercial/industrial areas presented increases in technical losses and voltage levels for high penetration levels. Rural areas presented reductions in these parameters for all levels of PVDG integration.

This study presents a model predictive control (MPC)-based centralised control approach for maintaining the voltages of the nodes within permissible limits in the presence of high photovoltaic (PV) penetration. The proposed control scheme coordinates the actions of on-load tap changer (OLTC) and PV inverters optimally to fulfil the desired objectives. The objectives are minimisation of change in control variables, slack variables, energy loss, and voltage error. These objectives are weighted to form the overall objective function. Three rules are formulated based on the severity of voltage magnitudes. The weights of the objectives are adjusted according to these pre-defined rules. Simulations are performed in an active distribution network (ADN) integrated with and without microgrids, where both demands and generations vary hourly over the day. As power is injected by the microgrids during most of the time of the day, the excursions of node voltages are slightly higher in the microgrids integrated ADN. Moreover, the incorporation of the proposed rule-based MPC drastically reduces the energy loss due to active power loss in distribution networks, as is evident from the simulation results obtained by comparing the proposed approach with an existing MPC-based approach. [ABSTRACT FROM AUTHOR]

The proliferation of photovoltaics (PV) in distribution systems brings about voltage stability problems. This paper proposes an algorithm to calculate extreme bifurcation intervals considering deep PV penetration levels. The paper applies the sandglass-hyper-ellipsoid-cone model to analyze the correlations among net bus loads representing bidirectional power flows for different PV penetration levels. Using the net bus load model, three extreme bifurcation points on voltage stability limit hypersurface are formulated where two of these points represent the voltage stability bifurcation interval in the forecasted net bus loading direction. An iterative method is applied to obtain bifurcation solutions. The validity of the proposed method is verified by using the IEEE 3-bus system, the IEEE 33-bus system and the IEEE 123-node test feeder. The numerical results demonstrate that the proposed sandglass-hyper-ellipsoid-cone net bus load model and solutions are effective in managing correlated net bus load forecast errors in distribution systems with PV integration. [ABSTRACT FROM AUTHOR]

Power systems have to be reinforced to accommodate a high penetration of renewable energy sources. Recent research shows that the stability margin of the grid degrades with the penetration of grid‐tied photovoltaic generators into the grid. In the model presented in the study, the critical level of photovoltaic penetration is associated with a Hopf bifurcation in the field dynamics of the synchronous generators which severely limits the operating domain of the grid. It is shown that the judicious introduction of synchronous condensers in the modelled grid delays this dynamic instability. A small‐signal analysis is performed for a system where the reactive power and inertial response is supplemented using a synchronous condenser. The study shows that the modified network tolerates much higher participation of photovoltaic generation in the grid. It is shown that the modified network retains the classical power system control approach and also does not demand a change in the way the photovoltaic generation is injected, thereby making it a natural implementation. The synchronous condenser augments the operational domain of the system significantly, nearly eliminating the need for renewable energy curtailment. A case‐study approach is used to present results on improvements in damping ratio, feasibility domain and transient stability. [ABSTRACT FROM AUTHOR]

This article proposes two strategies for the mitigation of power imbalances and related costs resulting from increasing PV penetration onto the Italian grid. New "state of the art" solar and netload day ahead forecast models were developed and applied to real data. These strategies consist of: (1) Improving the accuracy of PV and net load power forecast and enlarging the footprint of the controlled grid area; (2) Transforming unconstrained PV plants into "flexible PV plants": remotely controlled PV plants that can be proactively curtailed and work with cost-optimized Battery Energy Storage Systems. We demonstrate that the first strategy can effectively limit the imbalance impact when integrating a large share of PV generation, reducing imbalance volumes and costs, both at current and future solar penetration levels. We further demonstrate that the second strategy can entirely eliminate the imbalance impact of PV penetration, hence providing operational certainty to the TSO. Indeed, we show how flexible PV plants can be cost-optimally sized to set the imbalance volume at a desired target value regardless of PV installed capacity, hence allowing massive solar penetration. Finally, we show that the cost of implementing these strategies is less than the current cost of handling such imbalance impacts. • Strategies for mitigating imbalances from increasing PV penetration in Italian grid. • Flexible PV plants are proactively curtailed in tandem with cost-optimized batteries. • Cost of these strategies is less than the current cost of handling imbalance impacts. [ABSTRACT FROM AUTHOR]

Distributed generation from wind and solar acts on regional electric demand as a reduced consumption, giving rise to a "load shadowing effect". The net load becomes much more difficult to predict due to its dependence on the meteorological conditions. As a consequence, the growing penetration of variable generation increases the imbalance between demand and scheduled supply (net load forecast) and the reserve margins (net load uncertainty). The aim of this work is to quantify the benefit of the use of advanced probabilistic approaches rather than a traditional time-series method to assess the day-ahead reserves. For this purpose, several methods for load and net load uncertainty assessment have been developed and applied to a real case study considering also future solar penetration scenarios. The results show that, when forecasting only the load both traditional and probabilistic methods exhibit similar accuracy. Instead, in the case of net load prediction, i.e. when solar power is present, the probabilistic forecast can effectively limit the reserve margin needed to arrange the imbalance between residual demand and supply. The developed probabilistic approach provides a notable reduction of the Following Reserve which increases with the solar penetration: from 32.5% to 68.3% at 7% and 45% of penetration. • New probabilistic methods for the net-load uncertainty have been developed. • A new metric was introduced to certify the performance of the methods. • Probabilistic forecast limits reserve margin needed with growing solar penetration. [ABSTRACT FROM AUTHOR]

This work analyses the impact of photovoltaic generation on voltage stability margin in an islanded microgrid. An indicator of voltage collapse proximity, based on the maximum deliverable power, is used to study the contribution of photovoltaic generation to the voltage stability margin. In this context, the well-known power–voltage curves, also known as ‘nose’ curves, are developed, taking into account different levels of photovoltaic penetration. Furthermore, the effect of the power factor at the photovoltaic generators as well as the influence of the adopted model for such generators are also investigated. The results have shown that the photovoltaic generation can significantly affect the voltage stability margin.

With higher penetration of converter‐connected renewable energy sources (RES) into power systems, the successful operation of the system is challenged by significant reductions in system inertia. Presently, given the dominant share of the conventional synchronous power plant, RES power plants are not demanded to provide ancillary services. However, as RES connections increase, RES power plants will play a major role in power system operation, contributing to frequency control. This study demonstrates that photovoltaic power plants (PVPPs) can provide effectively different types of frequency support based on a power reserve and an offline maximum power point tracking (MPPT) technique. An innovative method to de‐load the PVPP without significantly increasing the MPPT complexity is proposed. Results from different PVPP frequency support methods, under varying levels of photovoltaic penetration, are presented which demonstrate their capability to provide inertia support comparable to that of synchronous generators. A new variable droop control method, which releases maximum power during the inertial response and returns to fixed droop gain value after a specified time is also presented. The results from using the variable droop show that the frequency nadir and the rate‐of‐change‐of‐frequency can be significantly reduced and some power reserve still maintained after a frequency event. [ABSTRACT FROM AUTHOR]

Highlights • Practical application of the regional PV power forecast. • The PV forecast is used for power transmission scheduling. • Benefits of PV power forecast are pointed out using a real case study. • Energy imbalance and its related costs has been evaluated. Abstract The increased penetration of photovoltaic power introduces new challenges for the stability of the electrical grid, both at the local and national level. Many different effects are caused by high solar power injection into the electric grid. Among them, the increased risk of imbalance between the actual and scheduled power transmission is of particular relevance. The consequence is the need to exchange larger amounts of dispatchable power on the balancing energy market. The aim of this work is to analyze and quantify the effects of PV penetration in a target region and to evaluate the energy and economic benefits of using day-ahead PV forecast for power transmission scheduling. For this purpose, we developed several data-driven methods for transmission scheduling that include day-ahead PV power forecasts. We compared the resulting operational imbalances from these new models against two reference models currently used by the local grid operators. In the case of no PV generation in the target area, the more accurate reference model leads to an imbalance of 3.6% of the peak power transmission while more accurate data-driven method reduces the imbalance to 3.2%. When the distributed PV capacity is not zero, the imbalance of the reference model grows from 5.15% (at the current penetration of 7%) to 9.8% (at the maximum planned regional penetration of 45%). When we apply the new scheduling model, imbalances are reduced to respectively 3.5% and 5.8% at 7% and 45% of penetration. Since in Italy the costs of imbalances resulting from distributed PV are borne by ratepayers, these costs are estimated to be respectively 2.3% and 15% of the average electricity bill at 7% and 45% penetration if the reference scheduling is used. When applying the new model these costs are respectively reduced to 1.2% and 8.5%. [ABSTRACT FROM AUTHOR]

Incentive‐based regulations, toward higher performance networks, are the main driver for minimising losses in distribution systems. On the other hand, more renewable generation is needed to achieve environmental targets. Hence, a multiobjective model is introduced in this study seeking to minimise energy losses as well as maximise renewable generation in radial distribution systems (RDSs). Two alternative control strategies of future smart grids such as reactive power management using adaptive power factor control and coordinated voltage control are considered in the optimisation problem. The problem is subjected to the various technical constraints such as voltage limits, thermal limits and reactive capability limits of photovoltaic (PV) penetration, power factor regulations and underload tap changer adjustment. Also, the uncertainties of load and renewable generation are considered, too. Then, the obtained non‐linear programming problem is relaxed and reformulated as a well‐suited and computationally efficient second‐order cone programming problems. To obtain more efficient and evenly distributed Pareto set to help decision‐making process, a modified normal boundary intersection method is introduced for solution methodology. The implementation of the proposed framework on IEEE 33‐bus RDSs shows the gains that the flexibility provided by innovative control strategies can have on energy loss reduction and PV capacity. [ABSTRACT FROM AUTHOR]

Current energy policies are encouraging the connection of power generation based on low-polluting technologies, mainly those using renewable sources to distribution networks. The photovoltaic (PV) systems have experienced a great growth around the word in last years. Hence, it becomes increasingly important to understand technical challenges, facing high penetration of PV systems at the grid, especially considering the effects of intermittence of this source on the power quality, reliability and stability of the electric distribution system. In another hand, the connections of distributed generators, by PV panels, changes voltage profile at low voltage power systems. This fact can affect the distribution networks on which they are attached causing overvoltage, undervoltage, frequency oscillations and changes in protection design. In order to predict these disturbs, because of this PV penetration, this article aims to analyze seven training algorithms used in artificial neural networks for temporal prediction of the generated active power and thus the state of the distribution network in which these microgenerators are connected and, then compare its best results with the Support Vector Machine (SVM) technique. As a result it was concluded that 3 algorithms are suitable for this type of analysis with the best performance among the seven analyzed was the Bayesian Regularization and that Artificial Neural Networks are more suitable for this problem than the SVM. [ABSTRACT FROM PUBLISHER]

Current energy policies are encouraging the connection of power generation based on low-polluting technologies, mainly those using renewable sources, to distribution networks. Hence, it becomes increasingly important to understand technical challenges, facing high penetration of PV systems at the grid, especially considering the effects of intermittence of this source on the power quality, reliability and stability of the electric distribution system. This fact can affect the distribution networks on which they are attached causing overvoltage, undervoltage and frequency oscillations. In order to predict these disturbs, artificial neural networks are used. This article aims to analyze 3 training algorithms used in artificial neural networks for temporal prediction of the generated active power thru photovoltaic panels. As a result it was concluded that the algorithm with the best performance among the 3 analyzed was the Levenberg-Marquadrt. [ABSTRACT FROM AUTHOR]

Integration of renewable energy sources into the electric grid in the domestic sector results in bidirectional energy flow from the supply side of the consumer to the grid. Traditional pricing methods are difficult to implement in such a situation of bidirectional energy flow and they face operational challenges on the application of price-based demand side management programme because of the intermittent characteristics of renewable energy sources. In this study, a dynamic pricing method using real-time data based on a cloud computing framework is proposed to address the aforementioned issues. The case study indicates that the dynamic pricing captures the variation of energy flow in the household. The dynamic renewable factor introduced in the model supports consumer oriented pricing. A new method is presented in this study to determine the appropriate level of photovoltaic (PV) penetration in the distribution system based on voltage stability aspect. The load flow study result for the electric grid in Kerala, India, indicates that the overvoltage caused by various PV penetration levels up to 33% is within the voltage limits defined for distribution feeders. The result justifies the selected level of penetration.

This paper presents a probabilistic approach in the modeling of stand-alone microgrids to predict their operational adequacy performance considering uncertainty of energy storage system (ESS), photovoltaic system (PVS) and conventional generator (CG). Instead of using the daily or hourly time step, operating period a minutely time step is considered to incorporate the effect of fast ramp up/down of system components on microgrid operating adequacy through expected energy not supplied (EENS) and expected energy not used (EENU), due to load and resource variations. A time varying state of charge (SOC) model is proposed to determine power output of an ESS in reliability modeling. The reliability of a PVS is modeled in detail based on the total cross-tied configuration (TCTC) of photovoltaic (PV) cells and arrays. The proposed technique and indices will be useful for system planners to select the type and size of microgrid systems that contain alternative energy sources and storage. [ABSTRACT FROM PUBLISHER]

The rapid growth of renewable energy applications in electric power systems dictates a need to develop comprehensive techniques that can be used to evaluate the economics involved and the reliability of power supply that can be achieved from the utilization of these energy sources. Photovoltaic (PV) arrays have the potential to significantly reduce operating costs in remote small systems which are generally supplied using costly diesel fuel. This paper presents a simulation method that provides objective indicators to help system planners decide on appropriate installation sites, selection of PV arrays or diesel units in capacity expansion and optimum PV penetration levels when utilizing PV energy in small isolated systems. [Copyright &y& Elsevier]