Integration Of Photovoltaic Generation Research Articles

Reconfigurable topology assessment for efficient allocation of photovoltaic generators in unbalanced power delivery networks

The three-phase power delivery systems are reliable and efficient means of delivering electric power to customer node points. However, the unequal distribution of loads over the three phases leads to unbalance voltage between phases, resulting in increased power losses in distribution transformers and lines. It is highly challenging to install photovoltaic (PV) generators in unbalanced power distribution networks (PDNs) to restore power supply efficiency. This paper proposes dynamic reconfiguration (DR) in unbalanced PDNs to foster efficient integration of PV generators and improve system performance. Since the demand for electricity at residential node points and the PV-generated power varies with the season, this study proposes a seasonal DR of the PDNs. A framework with multiple objectives has been proposed for the DR-coupled PV deployment problem. A novel value-adaptive weight-aggregated (VAWA) grey-wolf optimizer (GWO) has been synthesized to contribute to system performance enhancement. The proposed strategy was validated and established through comparative investigations on an Indian 19-bus and modified IEEE 123-bus unbalanced radial distribution systems (URDSs).

Incorporation of multiple random features kernel mean p‐power controller to elevate power quality in reconfigurable grid‐connected residential solar photovoltaic systems

SummaryProblems like intermittent photovoltaic (PV) power, disconnected PV arrays, etc. are brought on by the extensive integration of PV generation. In this article, a single‐stage PV‐integrated grid‐tethered system is controlled using a reconfigurative multiple random features kernel mean p‐power (MRFKMP) control algorithm. The algorithm circumvents the dependence of kernel parameter in the classic random Fourier features mapping and lower the computing complexity in the traditional multiple kernel learning adaptive filter. MRFKMP algorithm with a linear filter structure can reduce both the computational and storage cost. This is the novel application of MRFKMP algorithm to extract fundamental component of nonlinear load currents in PV‐integrated grid‐tied system. Furthermore, to increase the reliability of the system, a reconfigurable control is developed, which adaptive regulates DC link voltage from PV mode (PVM) during PV hours to active power filtering mode (AFM) during PV nonavailability/PV disconnection. On a created laboratory testbed, the applied control's practical feasibility for numerous scenarios is evaluated. Comparison with existing control algorithms reveals that the MRFKMP controller outperforms the LMF based PV system by 79% less peak‐to‐peak load current ripple and 60% less than the best performing SRF control algorithm. The grid current THD is 2.60%, which is 30% low than that presented by SRF technique.

Pre-feasibility study of a grid connected wind-PV hybrid system with energy storage and power prediction.

A simulation system using Matlab/ Simulink® for battery sizing in grid-connected renewable generation is compared with results from the optimization tool HOMER. The system is intended to reinforce remote weak distribution grids. The power injection of the hybrid generation system to the grid is defined by a power prediction method. The battery smoothes the power output and absorbs the prediction errors. As a reference, a wind – battery system is chosen. The impact of the integration of photovoltaic generation is studied. As an example for the meteorological conditions, wind data from the airport and solar irradiation mean values for Zaragoza are applied. Simulated renewable power ranges from 600 kW to 1.1 MW. The battery sizes obtained from the Matlab simulation differ substantially from HOMER results but show similarities. This is due to the difference in the battery models. Integration of solar generation can reduce battery size relative to total installed power and also reduce total cost of generated energy.

Use of Inverter-Based Air Conditioners to Provide Voltage Regulation Services in Unbalanced Distribution Networks

The large-scale integration of photovoltaic generation and electric vehicles results in over-voltage, under-voltage, and voltage unbalance problems in three-phase distribution networks. The power consumption of the air conditioners (ACs) is large among the daily electrical appliances and can be regulated to provide voltage regulation services. To protect occupants' privacy and utilize the existing dispatch strategy of the battery, we propose a thermal battery equivalent model of the inverter-based AC to regulate the active power and provide a voltage regulation service. Moreover, an improved Newton-Raphson power-flow algorithm is developed to reduce the computational burden. The affinity propagation method is applied to cluster ACs according to different operating states. Thus, the ACs' operating frequencies are adjusted to reset the corresponding operating power. The feasibility of the thermal battery equivalent model and voltage regulation algorithm is verified based on case studies utilizing the revised IEEE 33-node three-phase power distribution network.

Economic and Low-Carbon-Oriented Distribution Network Planning Considering the Uncertainties of Photovoltaic Generation and Load Demand to Achieve Their Reliability

The integration of renewable resources with distribution networks (DNs) is an effective way to reduce carbon emissions in energy systems. In this paper, an economic and low-carbon-oriented optimal planning solution for the integration of photovoltaic generation (PV) and an energy storage system (ESS) in DNs is proposed. A convolutional neural network (CNN)-based prediction model is adopted to characterize the uncertainties of PV and load demand in advance. Then, taking the lowest total economic cost, the largest carbon emission reduction, and the highest system power supply reliability as the optimization objectives, the optimal distribution network planning model is constructed. The improved multi-objective particle swarm optimization (MOPSO) algorithm is used to solve the optimization model, and the effectiveness of the proposed solution is confirmed through a comparative case study on the IEEE-33 bus system. Simulation results show that the proposed solution can better maintain the balance between economic cost and carbon emissions in DNs.

Integration of Photovoltaic Generation Within a Modeling Framework for Energy Hubs

Energy efficiency is a topic with many publications related to resource exploitation at a local scale; via well-performed energy management, substantial environmental and economic benefits can be achieved. In this article, the models used to forecast the photovoltaic power yield in two distinct facilities are described. These facilities are part of the same production plant, which makes use of different heterogeneous resources (carbon dioxide, water, thermal energy, and electricity) and has already been analyzed in a problem that consists in finding the set of variables that minimize the operation cost. In order to predict the power production for both photovoltaic fields, the expressions for radiation on sloped surfaces and the equivalent circuit for solar cells are employed, and the inverters and wire-transmission loss effects are considered. Furthermore, their integration within a general-purpose modeling framework for energy hubs is demonstrated. The comparison between validation results and production real data shows that despite the slight overestimation of the energy yield, the models are suitable to forecast the production of both facilities with a suitable accuracy, as the R2 coefficients of both facilities lie between 0.95 and 0.96.

Multi-objective Dynamic Reconfiguration for Urban Distribution Network Considering Multi-level Switching Modes

The increasing integration of photovoltaic generators (PVGs) and the uneven economic development in different regions may cause the unbalanced spatial-temporal distribution of load demands in an urban distribution network (UDN). This may lead to undesired consequences, including PVG curtailment, load shedding, and equipment inefficiency, etc. Global dynamic reconfiguration provides a promising method to solve those challenges. However, the power flow transfer capabilities for different kinds of switches are diverse, and the willingness of distribution system operators (DSOs) to select them is also different. In this paper, we formulate a multi-objective dynamic reconfiguration optimization model suitable for multi-level switching modes to minimize the operation cost, load imbalance, and the PVG curtailment. The multi-level switching includes feeder-level switching, transformer-level switching, and substation-level switching. A novel load balancing index is devised to quantify the global load balancing degree at different levels. Then, a stochastic programming model based on selected scenarios is established to address the uncertainties of PVGs and loads. Afterward, the fuzzy c-means (FCMs) clustering is applied to divide the time periods of reconfiguration. Further-more, the modified binary particle swarm optimization (BPSO) and Cplex solver are combined to solve the proposed mixed-in-teger second-order cone programming (MISOCP) model. Numerical results based on the 148-node and 297-node systems are obtained to validate the effectiveness of the proposed method.

Probabilistic Static Voltage Stability of Power System with Integration of PV Generators using Monte Carlo Simulations

As a renewable source, the uncertainties and intermittencies of solar irradiance have become the main concern in developing and integrating such power generation into an electricity network. In power system operation, it is important to maintain a stable voltage profile under random power injection from renewable power generations. The effect of photovoltaic (PV) power plants on the static voltage stability of the interconnected power system is presented in this paper. The probabilistic study was conducted through Monte Carlo Simulation (MCS) to investigate the fluctuation of voltage profiles under uncertain power injection from PV power plants. The standard test system of IEEE 14 bus and practical test system of Lombok, West Nusa Tenggara electricity network are investigated. It was noticed that the installation of a photovoltaic power plant affected the voltage profiles. The fluctuated condition of power injection from PV power plant resulted in more fluctuation of voltage profiles as indicated by higher standard deviation values. Moreover, distributed location of the PV power plant also influenced the circumstances of voltage fluctuation, providing less fluctuated condition of voltage profiles. Eventually, it can be observed that the voltage fluctuation would influence the static voltage stability of the interconnected power system.

Combined PV–EV hosting capacity assessment for a residential LV distribution grid with smart EV charging and PV curtailment

Photovoltaic (PV) systems and electric vehicles (EVs) integrated in local distribution systems are considered to be two of the keys to a sustainable future built environment. However, large-scale integration of PV generation and EV charging loads poses technical challenges for the distribution grid. Each grid has a specific hosting capacity limiting the allowable PV and EV share. This paper presents a combined PV–EV grid integration and hosting capacity assessment for a residential LV distribution grid with four different energy management system (EMS) scenarios: (1) without EMS, (2) with EV smart charging only, (3) with PV curtailment only, and (4) with both EV smart charging and PV curtailment. The combined PV–EV hosting capacity is presented using a novel graphical approach so that both PV and EV hosting capacity can be analyzed within the same framework. Results show that the EV smart charging can improve the hosting capacity for EVs significantly and for PV slightly. While the PV curtailment can improve the hosting capacity for PV significantly, it cannot improve the hosting capacity for EVs at all. From the graphical analysis, it can be concluded that there is a slight positive correlation between PV and EV hosting capacity in the case of residential areas. • Combined PV–EV grid integration study in a residential LV grid is presented. • A novel graphical analysis approach for combined PV–EV HC assessment is presented. • Both HC for PV and EV are analyzed in the same framework. • Smart EV charging and PV curtailment are included to assess possible HC enhancement. • Correlation between HC for PV and EV in the case of residential areas is obtained.

Photovoltaic Generation Integration with Radial Feeders Using GA and GIS

The electric power generated from different electricity sources are not used efficiently by end users in the world. This is due to the loss of power supplied in the case of electricity transmission and distribution to residential, commercial, and industrial loads. Even if the loss of power in the power system cannot be avoided 100%, it should be reduced to the minimum optimal value. The loss of power in the radial feeders can be minimized using an optimally allocated photovoltaic (PV) generation system by considering the information of geography, solar irradiance of the site, and space availability, which should not have shadow from large buildings and trees. The PV generation system eliminates the problem of power demand by enhancing the capacity of the power network as well as by reducing the depletion and consumption of fossil fuel resources. To reduce power loss and improve system loading capacity for demand response, the integration and finding the optimal place of photovoltaic generation take high concern from power system operators and technicians. The optimal allocation of PV has been done using the Genetic Algorithm (GA) for optimization of a multiobjective function with different constraints. The main objective of this paper is to minimize the power loss of the radial distribution networks by maintaining the phase voltage of the load in balance and improving the drop in voltage along the phase. So, GA is used to determine the best location and capacity of PV generation that can reduce the loss of power in the system. The IEEE-33 bus system is used to test the proposed method. Generally, using the GA and GIS methods results in a high accuracy for optimal placement of PV generation in the IEEE-33 bus radial feeder and enables to reduce the loss of power during transmission and distribution by maintaining the power quality for consumers.

Photovoltaic energy in South America: Current state and grid regulation for large-scale and distributed photovoltaic systems

Abstract This article presents an overview of the photovoltaic solar energy integration in the South American energy matrix. This work addresses aspects such as requirements established in the grid codes to connect solar plants to the power grid, the necessary protections for the connection of small-scale photovoltaic systems, the provision and prospects of ancillary services, and the energy and solar potential of the region. This research aims to highlight a summary of different aspects of connecting photovoltaic systems to the grid in eight countries in South America with similar socioeconomic development. In this way, it is possible to compare connection requirements and regulations for each country, resulting in a perspective of the best practices to introduce photovoltaic facilities in the region. As a result of the study, Chile is pointed out as the South American country with the highest penetration of photovoltaic energy due to the expressive levels of solar irradiation. It is also the country that presents the strictest criteria concerning the integration of photovoltaic generators to the electrical grid.

Comparison of Voltage Control by Inverters for Improving the PV Penetration in Low Voltage Networks

Voltage rise caused by reverse power flows and intermittency in renewable power is the main limiting factor for integration of photovoltaic(PV) generation in low voltage networks. Inverter voltage control techniques have been developed to provide effective voltage control and support higher penetration integration of PV generation. In this paper, the common Volt-VAR control, PF(P) and Q(U) control of photovoltaic inverter methods are detailed compared. A set of simulation study-cases have been designed based on a generic LV grid model, which is considered as representative for the Bornholm network. Observations of the influence of different Volt-VAR control strategies upon different electrical parameters on hosting capacity increase potential have been performed. Results show that inverter controls can greatly contribute the integration of PV in LV networks in the perspective of avoiding overvoltage.

Control Strategy of Intergrated Photovoltaic-UPQC System for DC-Bus Voltage Stability and Voltage Sags Compensation

Power quality problem, because of its various forms and occurrence frequency, has become one of the most critical challenges confronted by a power system. Meanwhile, the development of renewable energy has led to more demands for an integrated system that combines both merits of sustainable energy generation and power quality improvement. In this context, this paper discusses an integrated photovoltaic-unified power quality conditioner (PV-UPQC) and its control strategy. The system is composed of a series compensator, shunt compensator, dc-bus, and photovoltaic array, which conducts an integration of photovoltaic generation and power quality mitigation. The fuzzy adaptive PI controller and the improved Maximum Power Point Tracking (MPPT) technique are proposed to enhance the stability of dc-bus voltage, which is aimed at the power balance and steady operation of the whole system. Additionally, the coordinate control strategy is studied in order to ensure the normal operation and compensation performance of the system under severe voltage sag condition. In comparison to the existing PV-UPQC system, the proposed control method could improve the performance of dc-bus stability and the compensation ability. The dynamic behavior of the integrated system were verified by simulation in MATLAB and PLECS. Selected results are reported to show that the dc-bus voltage was stable and increased under severe situations, which validates the effectiveness of the proposed integrated PV-UPQC system and its control strategy.

A synergetic control architecture for the integration of photovoltaic generation and battery energy storage in DC microgrids

A control strategy for the integration of photovoltaics (PV) and battery energy storage (BES) in a DC microgrid ( μ G) is proposed. The method provides a unique control architecture for both islanding and grid-connected modes. Moreover, the method does not require the operating mode signal to detect the islanding or grid-connected operation of the μ G. Consequently, it alleviates switching between different sets of controllers, thus providing a smooth transfer between operation modes. A nonlinear control architecture based on a synergetic approach is used for the local control of the power converters. Simulation results are presented to show the system performance and to test the proposed control architecture for different operation scenarios.

A Gain Scheduling Wide-Area Damping Controller for the Efficient Integration of Photovoltaic Plant

With photovoltaic generation increasing, the wide-area oscillation has a vital influence on the long-distance power transmission of photovoltaic power. For an efficient integration of photovoltaic generation, a gain scheduling wide-area damping controller (WADC) is designed to guarantee system damping performance under a wide-area signal delay and a changing operating condition, which could be aggravated by the fluctuant and uncertain photovoltaic generation. A linear parameter-varying (LPV) model is proposed to represent all possible operating conditions within varying ranges of the photovoltaic generation and the load. Then, a tensor product (TP) model transformation is applied to transform the LPV model into a TP model. Based on the TP model, a parallel distributed compensation controller (PDC) framework is adopted to design the gain scheduling WADC, which is solved by linear matrix inequalities (LMIs) considering the accommodation to the random interval delay. In addition, a staircase basis function method is proposed to reduce the conservatism of LMIs within the PDC framework. The gain of the proposed WADC will be adjusted according to the operating condition acknowledged through the real-time scheduling and control center, once a wide-area oscillation is detected. Finally, the performance of the proposed WADC is verified by a 2-area 4-machine system and a 68-bus 16-machine system.

Probabilistic methodology for estimating the optimal photovoltaic capacity in distribution systems to avoid power flow reversals

The large-scale integration of photovoltaic generation (PVG) on distribution systems (DSs) preserving their technical constraints related to voltage fluctuations and active power (AP) flow is a challenging problem. Solar resources are accompanied by uncertainty regarding their estimation and intrinsically variable nature. This study presents a new probabilistic methodology based on quasi-static time-series analysis combined with the golden section search algorithm to integrate low and high levels of PVG into DSs to prevent AP flow in reverse direction. Based on the analysis of two illustrative case studies, it was concluded that the successful integration of PVG is not only related to the photovoltaic-cell manufacturing prices and conversion efficiency but also with the manufacturing prices of power electronic devices required for reactive power control.

Assessment of Dynamic Line Rating and Photovoltaic Generation Integration and its Impact on Energy Dispatch

This work presents the impact of including distributed generation, using photovoltaic generation (PV), in a power system considering a model of dynamic line rating (DLR). A methodology for the integration of PV generators and the DLR model into a power system was proposed. This methodology was validated by using four models of the system: The base case, the model including DLR, the base system with PV generation, and the model involving DLR integration with PV distributed generation. The integration of the models with data on generation and real-time environmental conditions was also described. This study was carried out in the National Laboratory for Smart Grids LAB+i at Universidad Nacional de Colombia in Bogota. According to the results of the study case that considered DLR and PV, the cost due to generation decreased 6.14% per day, whereas active power losses decreased 7.12% per day in comparison with the results obtained from the base system. The results showed the potential benefits and disadvantages of integrating new renewable generation sources and DLR as a solution to the current problems of constraints of transmission lines rating due to the power injection of these new sources. The results of this study conclude that it is feasible to incorporate PV generators into the nodes of the overloaded lines if the DLR model is used on these lines through the proposed methodology.

Unstable Operation of Photovoltaic Inverter From Field Experiences

This letter presents records of unstable operations in grid-connected photovoltaic generation plants. The instabilities involve a wide range of frequencies from tens to thousands of Hertz. Possible causes of the instabilities are discussed based on the literature survey. This letter suggests new industry standards or grid codes for photovoltaic generation integration should consider such practical challenges.

Impact of large‐scale photovoltaic generation integration structure on static voltage stability in China's Qinghai province network

Large-scale photovoltaic (PV) generations are integrated into China's Qinghai province network and challenging the system stability. This study focuses on static voltage stability analysis of Qinghai grid in consideration of high-penetration PV generation. The test system is based on the practical network structure of Qinghai grid. Different practical PV integration structures are, respectively, studied by discussing the influences of transmission line length, output power of PV plant and reactive power compensation capacity on system static voltage stability. The authors also compared different PV integration structures to study the effect of topology on static voltage stability. Simulation results are performed in the practical network structure of Qinghai grid. The analysis results can be used to provide guidance for system modification and thereby improve the system operation stability.

Power Quality Analysis of Integration Photovoltaic Generator to Three Phase Grid under Variable Solar Irradiance Level

Objective of research is to analyze the influence of solar irradiance and integration of photovoltaic (PV) generator to power quality of three phase grid on the constant temperature and load, based on changes in some level of integration of PV generator. Power quality aspects studied are fluctuation or changing, and harmonics of voltage and current on eight scenarios PV generator connected to three-phase grid, using passive filter circuit model double band pass (double tuned). Research shows that voltage and current values on the PCC bus before use double tuned passive filter on the condition only connect single generator is still stable. However, if the PV generator connected to the three phase grid, amounted to more than one generation, voltage and current grid becomes unstable (fluctuation). At the level of solar radiation remains, the greater number of PV generators connected to the grid three-phase, then the values of voltage and current THD increases. At the level of solar irradiance increases, average THD of voltage and current grid also increased. Avarage THD of voltage and current grid is reduced after double tuned passive filter installed. Therefore, double tuned passive filter able to improve profile of voltage and current THD grid as a result of the integration of a number of PV power generators in three-phase grid according IEEE Standard 519-1992. Simulation and analysis of this research use Matlab/Simulink.