Number Of Photovoltaic Systems Research Articles

Low-Voltage Network Modeling and Analysis with Rooftop PV Forecasts: A Realistic Perspective from Queensland, Australia

Recent years have seen a rapid uptake in distributed energy resources (DER). Such technologies pose a number of challenges to network operators, which ultimately can limit the amount of rooftop solar photovoltaic (PV) systems that can be connected to a network. The objective of this industry-based research was to determine the potential network effects of forecast levels of customer-owned rooftop solar PV on Energy Queensland’s distribution network and formulate functions that can be used to determine such effects without the requirement for detailed network modeling and analysis. In this research, many of Energy Queensland’s distribution feeders were modeled using DIgSILENT PowerFactory and analyzed with forecast levels of solar PV and customer load. Python scripts were used to automate this process, and quasi-dynamic simulation (QDSL) models were used to represent the dynamic volt–watt and volt–var response of inverters, as mandated by the Australian Standard AS/NZS 4777. In analyzing the results, linear relationships were revealed between the number of PV systems on a feeder and various network characteristics. Regression was used to form trend equations that represent the linear relationships for each scenario analyzed. The trend equations provide a way of approximating network characteristics for other feeders under various levels of customer-owned rooftop solar PV without the need for detailed modeling.

Optimal planning of a micro‐grid containing tidal barrage equipped to the hydro‐pumps

AbstractDue to the advantages of micro‐grids including power losses and voltage drops reduction, reliability improvement and reduction in transmission network cost, numerous clean micro‐grids including renewable resources such as wind, tidal and solar are developed in different countries of world. The investment cost of the renewable energy‐based generation units especially tidal barrages is high, and to generate the cost‐effective electricity from the renewable resources, the optimization process should be performed. In this paper, optimal planning of a micro‐grid containing energy storage device and new mixture of renewable resources including tidal barrage and photovoltaic system is performed. For this purpose, optimal characteristics of barrage type tidal plant including number of turbines, sluices and hydro‐pumps, turbine tip and hub diameters and sluice width are determined to maximum energy of tidal plant is generated. Then, number of photovoltaic systems and batteries are obtained to supply the required load in minimum cost. To optimize the objective functions, different heuristic approaches including particle swarm, genetic and imperial competitive algorithms (ICAs) are applied, in the paper. To study the effectiveness of the proposed approach, optimal planning of a micro‐grid is performed. It is deduced from the numerical results that the particle swarm method has performed best in determining the optimal solution.

Advanced voltage control method for improving the voltage quality of low-voltage distribution networks with photovoltaic penetrations

As the number of photovoltaic (PV) power generators connected to the distribution grid increases, applications of on-load tap changers (OLTCs), power conditioning systems, and static reactive power compensators are being considered to mitigate the problem of voltage violation in low voltage distribution systems. The reactive power control by power conditioning systems and static reactive power compensators can mitigate steep voltage fluctuations. However, it creates losses in generation opportunities. On the other hand, OLTCs are installed at the bases of distribution lines and can collectively manage the entire system. However, the conventional voltage control method, i.e., the line drop compensation (LDC) method, is not designed for the case in which a large number of PV systems are installed in the distribution network, which results in voltage violations above the limit of the acceptable range. This study proposes a method to determine the optimal LDC control parameters of the voltage regulator, considering the power factor of PV systems to minimize the magnitude of voltage violations based on the voltage profile analysis of low-voltage (LV) distribution networks. Specifically, during a measurement period of several days, the voltages at some LV consumers and pole transformers were measured, and the optimal parameters were determined by analyzing the collected data. The effectiveness of the proposed method was verified through a numerical simulation study using the actual distribution system model under several scenarios of PV penetration rates. Additionally, the difference in the effectiveness of voltage violation reduction was verified in the case where all the LV consumer’s consumer voltage data measured per minute were used as well as in the case where only the maximum and minimum values of the data within the measurement period were used. The results reveal that the proposed method, which operates within the parameters determined by the voltage analysis of the LV distribution network, is superior to the conventional method. Furthermore, it was found that even if only the maximum and minimum values of the measurement data were used, an effective voltage violation reduction could be expected.

Review of Renewable Energy Technologies Utilized in the Oil and Gas Industry

In this study, applications of renewable energy technologies in the oil and gas industry were analyzed. A number of photovoltaic systems were investigated as applications for providing electric power to production facilities (i.e. the oil fields of Midway-Sunset, Kern River and Louisiana Bayou in the United States). Wind power systems were studied in the oil fields of Suizhong 36-1 (China), Beatrice (UK) and Utsira Nord (Norway). The geothermal power systems studied included the oil fields of Rocky Mountain (USA) and Fort Liard (Canada). Moreover, solar thermal systems in the oil fields of Mckittrick (USA), Caolinga (USA) and Amal (Oman) were examined as applications for providing thermal energy to production facilities. From the results, this study revealed that a variety of renewable energy technologies are currently used in the oil and gas industry. In particular, solar thermal systems are being actively studied for provision of the thermal energy required to enhance oil recovery.

A novel approach for optimal combinations of wind, PV, and energy storage system in diesel-free isolated communities

A new approach for optimal combinations of Hybrid Renewable Energy Systems (HRESs) is proposed, for diesel-free remote communities and related decision-making problems. The objective of the design is to satisfy the load with total cost’s minimization considering related constraints, where all analytical equations are given. The proposed system is a DC configuration for renewable energy integration in which Wind Turbines (WTs) are connected to the DC bus and the battery system removes the fluctuations in the DC bus. The WT is assumed to be well controlled to obtain the power curve and provide proper electricity to the grid. It is found that WT and Photovoltaic (PV) systems should be considered simultaneously on diesel-free generation islands to achieve a reliable and optimized configuration. A novel strategy is introduced for determining the range of batteries, which can be determined using the renewable energy potential to satisfy the load. It is also demonstrated that WTs are an essential power component in real HRES installations. It is illustrated that the range of WT operation must be first taken into account in real installations. Increasing WT fraction from an initial value, for instance 8%, to a desired value of about 33%, can lead to significant reductions in total cost as well as in the number of PV systems and batteries, even if the WT cost is significantly higher than that of PVs. A WT fraction higher than approximately 50% should not be considered. Finally, discussions are extended to consider the optimum WT fraction in a HRES.

Network Coordinated Power Point Tracking for Grid-Connected Photovoltaic Systems

Maximum power point tracking (MPPT) achieves maximum power output for a photovoltaic (PV) system under various environmental conditions. It significantly improves the energy efficiency of a specific PV system. However, when an increasing number of PV systems are connected to a distribution grid, MPPT poses several risks to the grid: 1) over-voltage problem, i.e., voltage in the distribution grid exceeds its rating; and 2) reverse power-flow problem, i.e., power that flows into the grid exceeds an allowed level. To solve these problems, power point tracking of all PV systems in the same distributed grid needs to be coordinated via a communication network. Thus, coordinated power point tracking (CPPT) is studied in this paper. First, an optimization problem is formulated to determine the power points of all PV systems, subject to the constraints of voltage, reverse power flow, and fairness. Conditions that obtain the optimal solution are then derived. Second, based on these conditions, a distributed and practical CPPT scheme is developed. It coordinates power points of all PV systems via a communication network, such that: 1) voltage and reverse power flow are maintained at a normal level; and 2) each PV system receives a fair share of surplus power. Third, a wireless mesh network (WMN) is designed to support proper operation of the distributed CPPT scheme. CPPT is evaluated through simulations that consider close interactions between WMN and CPPT. Performance results show that: 1) CPPT significantly outperforms MPPT by gracefully avoiding both overvoltage and reverse power-flow problems; 2) CPPT achieves fair sharing of surplus power among all PV systems; and 3) CPPT can be reliably conducted via a WMN.

Day Ahead Global Solar Radiation Forecasting Using Binary Trees and Factor Analysis

SUMMARY A method is proposed for forecasting global solar radiation. The method is based on weather information using binary trees and factor analysis. The feature of this method is that it is possible to use a simple linear forecasting equation. The method has been tested on meteorological and global solar radiation data obtained at several observation sites, and the results show that it is a promising means of maintaining the balance between demand and supply of electric power in power systems of the near future with a large number of photovoltaic systems installed.

Impacts of global electrification based upon photovoltaic technologies

The impacts of global electrification based upon photovoltaic technologies are examined and estimated from the following points of view: the number of photovoltaic systems in place, the power being delivered by them, the number of persons benefiting from the power being delivered, the total sales and economic benefits, and the number of jobs being created in manufacturing and installing them. Particular attention is given to estimated impacts on global electrification for rural (off-grid) populations in developing countries. The role of photovoltaic power technology as an enabling technology is discussed. Also, the growing impact of photovoltaic power technology as a competitive power technology for grid-connected needs is examined relative to its developing role as an alternative supplier of global electric power in competition with utility-generated power currently dominated by fossil- and nuclear-fueled electric generating plants. Finally, the positive impacts on the earth's environment as a result of generating electric power using photovoltaic technology are discussed relative to not producing carbon dioxide and other gases along with fuel wastes. Published by Elsevier Science Ltd.

瞬時出力変動値制御による太陽光発電のアイランデイング防止方式

Islanding of the utility interconnected photovoltaic (PV) systems mainly installed in residential houses is a most serious problem for safety of utility distribution lines. Output power variation method is one of the recommended measures in the Japanese guidelines on utility interconnection. However, the effectiveness of the measure decreases in the case of parallel operation of PV systems because of a counteraction of output power variation from each system. A new output power variation method applicable to parallel operation of PV systems was examined in this paper through simulation studies, using the simulation method developed based on demonstration tests in Rokko Island. The major results of the study are follows:- A new output power variation method was proposed in order to match frequency and phase of power variation among PV systems. In the method, phase angle of inverter output current is continuously modulated with instantaneous voltage signal of distribution line.- The simulation results on the proposed method shows that even when a number of PV systems are operated, islanding can be prevented securely while maintaining power quality of inverter output in nomal operation. This suggests that proposed output power variation method can be applied to actual field.