Small power tapping limit on dc-link of VSC HVDC transmission system

Abstract Power tapping from HVDC transmission corridor to serve rural areas has been the focus of many researchers and network planners. The tapping stations are to be of small power ratings so that it will not interfere with the main control and stability of the HVDC network. Several research works have assumed tap-off of different percentages of the main HVDC terminal rating without justification. This paper therefore proposes a simple analytical technique used to determine power tapping limit on DC-link of a VSC HVDC network. Effect of power tapping below and above the analytical tap limit is illustrated by results from simulation carried out in Matlab/Simulink, hence validating the proposed technique

Assessing possible energy potential in a food and beverage industry: Application of IDA-ANN-DEA approach

In the food and beverage industry, where growing, processing, packaging, distribution, storage, preparation, serving and disposing of food is the order of the day; energy consumption becomes an important input. Various energy models have been developed since the early 1970s, the period when energy caught the attention of policymakers due to the sudden price increase. Among the models are the index decomposition analysis (IDA), artificial neural network (ANN) and data envelopment analysis (DEA). The purpose of this study is to combine the strengths of these models, i.e., IDA, ANN and DEA, to allow biases in one model to offset biases in the other, so as to examine the effectiveness of energy management policies in a particular food and beverage industry. The integrated model applied to the food and beverage revealed that approximately 11% of energy consumed could be saved

Assessing possible energy potential in a food and beverage industry: Application of IDA-ANN-DEA approach

In the food and beverage industry, where growing, processing, packaging, distribution, storage, preparation, serving and disposing of food is the order of the day; energy consumption becomes an important input. Various energy models have been developed since the early 1970s, the period when energy caught the attention of policymakers due to the sudden price increase. Among the models are the index decomposition analysis (IDA), artificial neural network (ANN) and data envelopment analysis (DEA). The purpose of this study is to combine the strengths of these models, i.e., IDA, ANN and DEA, to allow biases in one model to offset biases in the other, so as to examine the effectiveness of energy management policies in a particular food and beverage industry. The integrated model applied to the food and beverage revealed that approximately 11% of energy consumed could be saved

Statistical analysis of wind speed and wind power potential of Port Elizabeth using Weibull parameters

This paper analyses wind speed characteristics and wind power potential of Port Elizabeth using statistical Weibull parameters. A measured 5–minute time series average wind speed over a period of 5 years (2005 - 2009) was obtained from the South African Weather Service (SAWS). The results show that the shape parameter (k) ranges from 1.319 in April 2006 to 2.107 in November 2009, while the scale parameter (c) varies from 3.983m/s in May 2008 to 7.390 in November 2009.The average wind power density is highest during Spring (September–October), 256.505W/m2 and lowest during Autumn (April-May), 152.381W/m2. This paper is relevant to a decision-making process on significant investment in a wind power project

Statistical analysis of wind speed and wind power potential of Port Elizabeth using Weibull parameters

This paper analyses wind speed characteristics and wind power potential of Port Elizabeth using statistical Weibull parameters. A measured 5–minute time series average wind speed over a period of 5 years (2005 - 2009) was obtained from the South African Weather Service (SAWS). The results show that the shape parameter (k) ranges from 1.319 in April 2006 to 2.107 in November 2009, while the scale parameter (c) varies from 3.983m/s in May 2008 to 7.390 in November 2009.The average wind power density is highest during Spring (September–October), 256.505W/m2 and lowest during Autumn (April-May), 152.381W/m2. This paper is relevant to a decision-making process on significant investment in a wind power project

Minimizing the Impact of Intermittent Wind Power on Multiperiod Power System Operation with Pumped Hydro Generation

In power system operations, unforeseen energy imbalances commonly occur, resulting in unexpected constraints on the system. This leads to a disturbance in normal operation. In systems with integration of large intermittent wind power resources, additional complications are imposed on the system, especially under heavy winds that require immediate measures to minimize possible impact of abrupt wind power fallout. Effective power system fortifications have to be put in place to address the challenges. Wind varies more on the sub-hourly time scales; therefore, sub-hourly dispatch is bound to address more of these issues than commonly used hourly methods. Hybrid power system operation with wind necessitates the use of fast start-up generation and storage to improve quality of power. In this work, the impact of intermittent wind power curtailment on power system operation is addressed to prevent system instability. A modified wind turbine power curve is used to restrict the onset of the normal cut-off point, thereby allowing sufficient time for effective power switchover with pumped hydro generation. This improves the voltage stability of the power system during curtailment. Singular value decomposition matrix of the power system network is employed to evaluate the performance of the proposed method

Optimal Allocation of Renewable Energy Hybrid Distributed Generations for Small-Signal Stability Enhancement

This paper solves the allocation planning problem of integrating large scale renewable energy hybrid distributed generations and capacitor banks into the distribution systems. Extraordinarily, the integration of renewable energy hybrid distributed generations such as solar photovoltaic, wind, and biomass takes into consideration the impact assessment of variable generations from PV and wind on the distribution networks’ long term dynamic voltage and small-signal stabilities. Unlike other renewable distributed generations, the variability of power from solar PV and wind generations causes small-signal instabilities if they are sub-optimally allocated in the distribution network. Hence, the variables related to small-signal stability are included and constrained in the model, unlike what is obtainable in the current works on the planning of optimal allocation of renewable distributed generations. Thus, the model is motivated to maximize the penetration of renewable powers by minimizing the net present value of total cost, which includes investment, maintenance, energy, and emission costs. Consequently, the optimization problem is formulated as a stochastic mixed integer linear program, which ensures limited convergence to optimality. Numerical results of the proposed model demonstrate a significant reduction in electricity and emission costs, enhancement of system dynamic voltage and small-signal stabilities, as well as improvement in welfare costs and environmental goodness

Selection of a Hybrid Renewable Energy Systems for a Low-Income Household

The use of a single criterion in the selection of the most suitable hybrid renewable energy system (HRES) has been reported to be inadequate in terms of sustainability. In order to fill this gap, this study presents a multi-criteria approach for the selection of HRES for a typical low-income household. The analysis is based on two energy demand scenarios viz: consumer demand based on energy efficient equipment (EET) and consumer energy demand without energy efficiency. The optimization of the HRES is performed using hybrid optimization of multiple energy renewables (HOMER) while the multi-criteria analysis is carried out using Criteria Importance Through Intercriteria Correlation (CRITIC) and the Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS). Results show that the optimal HRES alternative returned based on both energy demand scenarios is a PV/GEN/BAT system. The analysis further shows that a reduction of 44.6% in energy demand through EET leads to: 51.38% decrease in total net present cost, 11.90% decrease in cost of energy, 96.61% decrease in CO 2 emission and 193.94% increase in renewable fraction. Furthermore, the use of multi-criteria approach for HRES selection has an influence in the selection and ranking of the most suitable HRES alternatives. Overall, the application of EETs is environmentally and economically beneficial while the application of MCDM can help decision makers make a comprehensively informed decision on the selection of the most suitable HRES

Compressed Air Energy Storage as a Battery Energy Storage System for Various Application Domains: A Review

The recent increase in the use of carbonless energy systems have resulted in the need for reliable energy storage due to the intermittent nature of renewables. Among the existing energy storage technologies, compressed-air energy storage (CAES) has significant potential to meet techno-economic requirements in different storage domains due to its long lifespan, reasonable cost, and near-zero self-decay. When viewed as a battery system, the key performance metrics of CAES, like energy density (ED), round trip efficiency (RTE), and the depth of discharge (DoD), have poor values when compared with other battery technologies in similar domains. This prevents CAES from transitioning to a state-of-the-art form of energy storage. This paper reviews the transition of CAES concepts from carbonized to carbonless types of CAES, along with different single-objective optimization strategies and their effects on the overall system’s performance. It was discovered that competing performance metrics attributes cause single-objective optimization to have trade-offs that worsen at least one other preferred metric. The topology limitations of the generic CAES design were noted to prevent its use in different domains. To ensure that the optimal convergence of subsystem parameters is retained during charging and discharging periods, a suitable topology and subunit combinations for different domains are necessary. Possible options for solving these problems are identified so that the effects of the trade-offs imposed by optimization are either suppressed or eliminated

Non-Conventional, Non-Permanent Magnet Wind Generator Candidates

Global industrialization, population explosion and the advent of a technology-enabled society have placed dire constraints on energy resources. Furthermore, evident climatic concerns have placed boundaries on deployable energy options, compounding an already regrettable situation. It becomes apparent for modern renewable energy technologies, including wind generators, to possess qualities of robustness, high efficiency, and cost effectiveness. To this end, direct-drive permanent magnet (PM) wind generators, which eliminate the need for gearboxes and improve wind turbine drivetrain reliability, are trending. Though rare-earth PM-based wind generators possess the highly sought qualities of high-power density and high efficiency for direct-drive wind systems, the limited supply chain and expensive pricing of the vital raw materials, as well as existent demagnetization risks, make them unsustainable. This paper is used to provide an overview on alternative and viable non-conventional wind generators based on the so-called non-PM (wound-field) stator-mounted flux modulation machines, with prospects for competing with PM machine variants currently being used in the niche direct-drive wind power generation industry