Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications

An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics

Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications

An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics

A Novel Approach for the Power Ramping Metrics

One of the biggest concerns associated with incorporating a large amount of renewable energy into power systems is the need to cope with significant ramps in renewable power output. Power system operators need to have statistical information on the power ramping features of renewable generation, load, and net-load that can be used to mitigate ramping events in the case of a large forecast error to ensure the power system's flexibility and reliability; on the other hand, for economic considerations. So far, there is no consensus on a precise definition for the ramp event and so far there are hardly any metrics describing the ramping features of a power system. The paper introduces new metrics describing the power ramping features in a power system. The new metrics are ramp regularity factor (RRF), ramp intensity factor (RIF), and maximum ramp ratio (MRR). In addition, the coefficient of variation (CV) is used to characterize the average value of power ramps. The new ramp metrics are applied to the output power of Belgium's aggregated wind farms in 2017 and 2018. The results obtained by comparing the two years demonstrate that the two years have the same ramping behavior, although the average installed wind capacity has been increased. The new metrics can also be applied to other renewable sources (PV, tidal power, etc.), load, and net-load at any stage of operation

Wind Power Ramps Analysis for High Shares of Variable Renewable Generation in Power Systems

Power system operators should be provided with more information on the characteristics of variable generation power ramps because, although there has been an improvement in the forecasting of wind power, the percentage of error in forecasting is still high to some extent. As a result of the ongoing rise in the participation rate of variable generation, this error will have a significant impact on the balance of power generation and consumption. From the grid operators' viewpoint, in order to balance these ramp events, it is important to get the scale of ramp events in the system as well as the times during which collective events are most likely to arise in order to achieve flexibility and reliability in the power system. Digitization of power systems brings big data which opening opportunities for improving the efficiency of power system operation. This paper analyzes the historical data of power-time curve in two directions: vertical and horizontal, in order to gain details on the behavior of wind power ramps. The method of analysis will be demonstrated by an analysis of actual historical output power of aggregated Belgian wind farms every 15 minutes in 2017 and 2018. Comparing the results of the two years outlined that there are fixed percentages related to wind power ramping behavior and even if the wind capacity is increased, it is possible to determine the extent of these ramps

Neural Network based Short Term Forecasting Engine To Optimize Energy And Big Data Storage Resources Of Wireless Sensor Networks

Energy efficient wireless networks is the primary research goal for evolving billion device applications like IoT, smart grids and CPS. Monitoring of multiple physical events using sensors and data collection at central gateways is the general architecture followed by most commercial, residential and test bed implementations. Most of the events monitored at regular intervals are largely redundant/minor variations leading to large wastage of data storage resources in Big data servers and communication energy at relay and sensor nodes. In this paper a novel architecture of Neural Network (NN) based day ahead steady state forecasting engine is implemented at the gateway using historical database. Gateway generates an optimal transmit schedules based on NN outputs thereby reducing the redundant sensor data when there is minor variations in the respective predicted sensor estimates. It is observed that NN based load forecasting for power monitoring system predicts load with less than 3% Mean Absolute Percentage Error (MAPE). Gateway forward transmit schedules to all power sensing nodes day ahead to reduce sensor and relay nodes communication energy. Matlab based simulation for evaluating the benefits of proposed model for extending the wireless network life time is developed and confirmed with an emulation scenario of our testbed. Network life time is improved by 43% from the observed results using proposed model

Earth-observation-based estimation and forecasting of particulate matter impact on solar energy in Egypt

This study estimates the impact of dust aerosols on surface solar radiation and solar energy in Egypt based on Earth Observation (EO) related techniques. For this purpose, we exploited the synergy of monthly mean and daily post processed satellite remote sensing observations from the MODerate resolution Imaging Spectroradiometer (MODIS), radiative transfer model (RTM) simulations utilizing machine learning, in conjunction with 1-day forecasts from the Copernicus Atmosphere Monitoring Service (CAMS). As cloudy conditions in this region are rare, aerosols in particular dust, are the most common sources of solar irradiance attenuation, causing performance issues in the photovoltaic (PV) and concentrated solar power (CSP) plant installations. The proposed EO-based methodology is based on the solar energy nowcasting system (SENSE) that quantifies the impact of aerosol and dust on solar energy potential by using the aerosol optical depth (AOD) in terms of climatological values and day-to-day monitoring and forecasting variability from MODIS and CAMS, respectively. The forecast accuracy was evaluated at various locations in Egypt with substantial PV and CSP capacity installed and found to be within 5–12% of that obtained from the satellite observations, highlighting the ability to use such modelling approaches for solar energy management and planning (M&P). Particulate matter resulted in attenuation by up to 64–107 kWh/m2 for global horizontal irradiance (GHI) and 192–329 kWh/m2 for direct normal irradiance (DNI) annually. This energy reduction is climatologically distributed between 0.7% and 12.9% in GHI and 2.9% to 41% in DNI with the maximum values observed in spring following the frequent dust activity of Khamaseen. Under extreme dust conditions the AOD is able to exceed 3.5 resulting in daily energy losses of more than 4 kWh/m2 for a 10 MW system. Such reductions are able to cause financial losses that exceed the daily revenue values. This work aims to show EO capabilities and techniques to be incorporated and utilized in solar energy studies and applications in sun-privileged locations with permanent aerosol sources such as Egypt

A New Economic Dispatch for Coupled Transmission and Active Distribution Networks Via Hierarchical Communication Structure

Traditionally, the economic dispatch problem (EDP) of the bulk generators connected to transmission networks (TNs) is solved in a centralized dispatching center (CDC) while modeling distribution networks as passive loads. With the increasing penetration levels of distributed generation, coordinating the economic dispatch between TNs and active distribution networks (ADNs) became vital to maximizing system efficiency. This article proposes a hierarchical communication structure, which requires minimal upgrades to the CDC, for solving the EDP of coupled TNs and ADNs. Based on the minimal data transfer between the CDC and distribution network operators, the problem is formulated and solved while considering the network losses in both TNs and ADNs. Furthermore, a sensitivity analysis is conducted to assess the effect of the ratio of the distribution lines on the economic dispatch solution and the operational cost of the system. The numerical results demonstrate the effectiveness of the proposed centralized scheme and highlight the significance of considering the network losses of both TNs and ADNs when solving the EDP. The results show that the proposed framework can achieve savings of up to 17.98% by taking into account the network losses of TNs and ADNs

Integrating Features of Islamic Traditional Home and Smart Home

Architecture is a mirror that reflects the various elements of its environment and surroundings, such as climate, geographical characteristics, standard architectural principles, and social, cultural and scientific developments. Muslims of different regions were able, through architecture, to portray their temperaments and environments, free of external influence and guarantee life goals for users. Every day, building owners and occupants experience the constant challenges of comfort, convenience, cost, productivity, performance and sustainability. Owners, designers, builders, and operators are continuously faced with new processes, technologies and offerings to help them achieve better building performance. Since an intelligent building is run by a “system of systems” that is integrated to deliver a higher level of operational efficiency and an improved set of user-interface tools than are usually found in traditional building automation; at the other hand Arab homes with Islamic Identity guarantee all life goals for use.. Hence, this research focus on the smart environmental treatments of Islamic features for traditional architecture in Arabs homes, features of smart home and life goals for resident users.Trying to achieve a methodology combining them for enriching Arab experience of traditional architecture and its architectural results, with the modern trends of smart architecture. This combination aims at creating a residential model combining the benefits and features of Arab Islamic identity and intelligent design

The optimum PV plant for a given solar DC/AC converter

In recent years, energy production by renewable sources is becoming very important, and photovoltaic (PV) energy has became one of the main renewable sources that is widely available and easily exploitable. In this context, it is necessary to find correct tools to optimize the energy production by PV plants. In this paper, by analyzing available solar irradiance data, an analytical expression for annual DC power production for some selected places is introduced. A general efficiency curve is extracted for different solar inverter types, and by applying approximated function, a new analytical method is proposed to estimate the optimal size of a grid-connected PV plant linked up to a specific inverter from the energetic point of view. An exploitable energy objective function is derived, and several simulations for different locations have been provided. The derived analytical expression contains only the available data of the inverter (such as efficiency, nominal power, etc.) and the PV plant characteristics (such as location and PV nominal power)

Convolutional Neural Network with Genetic Algorithm for Predicting Energy Consumption in Public Buildings

Abdelaziz, A., Santos, V., & Dias, M. S. (2023). Convolutional Neural Network with Genetic Algorithm for Predicting Energy Consumption in Public Buildings. IEEE Access. https://doi.org/10.1109/ACCESS.2023.3284470---This work has been supported by Portuguese funds through FCT - Fundação para a Ciência e Tecnologia, I.P., under the project FCT UIDB/04466/2020, and this work has been supported by Information Management Research Center (MagIC) - NOVA Information Management School.Due to their capacity to improve energy consumption performance, intelligent applications have recently assumed a pivotal position in the energy management of public buildings. Because of their irregular energy consumption patterns and the lack of design criteria for energy efficiency and sustainability solutions, keeping these buildings’ energy consumption under control is a significant issue. As a result, it is important to analyze public building energy consumption patterns and forecast future energy demands. Evidence like this highlights the need to identify and categorize energy use trends in commercial and institutional structures. This research aims to identify the most effective intelligent method for categorizing and forecasting the energy consumption levels of public buildings and, ultimately, to identify the scientific rules (If-Then rules) that will aid decision-makers in establishing the energy consumption level in each building. The goals of this research were accomplished by employing two intelligent models, the Elbow technique and the Davis and Boulden approach, to count the number of clusters of energy consumption patterns. It was determined what the clustering levels would be in each structure using K-means and a genetic algorithm. In this step, the genetic algorithm was utilized to find the best centroid points for each cluster, allowing the fitting model to function better. Determining which buildings use the most energy has been made easier thanks to the extraction of If-Then rules from cluster analysis. Convolutional neural networks (CNNs) and CNNs combined with a genetic algorithm were also employed as intelligent models for energy consumption forecasting. At this point, we utilized a genetic algorithm to fine-tune some of CNN’s settings. CNN with genetic algorithm outperforms on CNN model in terms of accuracy and standard error. Using a genetic algorithm, CNN achieves a 99.01% accuracy on the training dataset and a 97.74% accuracy on the validation dataset, with accuracy and an error of 0.02 and 0.09, respectively. CNN achieves a 98.03% accuracy and a 0.05 standard error on the training dataset and a 94.91% accuracy and a 0.26 standard error on the validation dataset. This research is useful for policymakers in the energy sector because it allows them to make informed decisions about the timing of energy supply and demand for public buildings.authorsversionepub_ahead_of_prin