Pub Date : 2020-01-01DOI: 10.37247/aderes2edn.2.2020.9
T. Dawid, Sobota Tomasz, Jaremkiewicz Magdalena, Taler Jan
The paper presents the medium temperature monitoring system based on digital proportional-integral-derivative (PID) control. For industrial thermometers with a complex structure used for measuring the temperature of the fluid under high pressure, the accuracy of the first-order model is inadequate. A second-order differential equation was applied to describe a dynamic response of a temperature sensor placed in a heavy thermowell (industrial thermometer). The quality of the water temperature control system in the tank was assessed when measuring the water temperature with a jacketed thermocouple and a thermometer in an industrial casing. A thermometer of a new design with a small time constant was also used to measure temperature. The quality of water temperature control in the hot water storage tank was evaluated using a classic industrial thermometer and a new design thermometer. In both cases there was a K-type sheathed thermocouple inside the thermowell. Reductions in the time constant of the new thermometer are achieved by means of a steel casing with a small diameter hole inside which the thermocouple is precisely fitted. The time constants of the thermometers were determined experimentally with a jump in water temperature. A digital controller was designed to maintain the preset temperature in an electrically heated hot water tank. The function of the regulator was to adjust the power of the electrical heater to maintain a constant temperature of the liquid in the tank.
{"title":"Influence of the Thermometer Inertia on the Quality of Temperature Control in a Hot Liquid Tank Heated with Electric Energy","authors":"T. Dawid, Sobota Tomasz, Jaremkiewicz Magdalena, Taler Jan","doi":"10.37247/aderes2edn.2.2020.9","DOIUrl":"https://doi.org/10.37247/aderes2edn.2.2020.9","url":null,"abstract":"The paper presents the medium temperature monitoring system based on digital proportional-integral-derivative (PID) control. For industrial thermometers with a complex structure used for measuring the temperature of the fluid under high pressure, the accuracy of the first-order model is inadequate. A second-order differential equation was applied to describe a dynamic response of a temperature sensor placed in a heavy thermowell (industrial thermometer). The quality of the water temperature control system in the tank was assessed when measuring the water temperature with a jacketed thermocouple and a thermometer in an industrial casing. A thermometer of a new design with a small time constant was also used to measure temperature. The quality of water temperature control in the hot water storage tank was evaluated using a classic industrial thermometer and a new design thermometer. In both cases there was a K-type sheathed thermocouple inside the thermowell. Reductions in the time constant of the new thermometer are achieved by means of a steel casing with a small diameter hole inside which the thermocouple is precisely fitted. The time constants of the thermometers were determined experimentally with a jump in water temperature. A digital controller was designed to maintain the preset temperature in an electrically heated hot water tank. The function of the regulator was to adjust the power of the electrical heater to maintain a constant temperature of the liquid in the tank.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":"1 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69679537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-01DOI: 10.37247/aderes2edn.2.2020.3
L. Si, W. Cao, Xiangping Chen
This paper proposes an innovative approach for controlling pollutant release in a long-distance tunnel via longitudinal ventilation. Enhanced by an active disturbance rejection control (ADRC) method, a ventilation controller is developed to regulate the forced air ventilation in a road tunnel. As a result, the pollutants (particulate matter and carbon monoxide) are reduced by actively regulating the air flow rate through the tunnel. The key contribution of this study lies in the development of an extended state observer that can track the system disturbance and provide the system with compensation via a nonlinear state feedback controller equipped by the ADRC. The proposed method enhances the disturbance attenuation capability in the ventilation system and keeps the pollutant concentration within the legitimate limit in the tunnel. In addition to providing a safe and clean environment for passengers, the improved tunnel ventilation can also achieve better energy saving as the air flow rate is optimized.
{"title":"New Disturbance Rejection Method for Energy Efficient Tunnel Ventilation","authors":"L. Si, W. Cao, Xiangping Chen","doi":"10.37247/aderes2edn.2.2020.3","DOIUrl":"https://doi.org/10.37247/aderes2edn.2.2020.3","url":null,"abstract":"This paper proposes an innovative approach for controlling pollutant release in a long-distance tunnel via longitudinal ventilation. Enhanced by an active disturbance rejection control (ADRC) method, a ventilation controller is developed to regulate the forced air ventilation in a road tunnel. As a result, the pollutants (particulate matter and carbon monoxide) are reduced by actively regulating the air flow rate through the tunnel. The key contribution of this study lies in the development of an extended state observer that can track the system disturbance and provide the system with compensation via a nonlinear state feedback controller equipped by the ADRC. The proposed method enhances the disturbance attenuation capability in the ventilation system and keeps the pollutant concentration within the legitimate limit in the tunnel. In addition to providing a safe and clean environment for passengers, the improved tunnel ventilation can also achieve better energy saving as the air flow rate is optimized.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":"1 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69679584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-12-05DOI: 10.11648/J.IJEEE.20190406.11
Wu Mingran, Zhao Min, Wu Zhaodan
Based on time series data from 1990 to 2016, an empirical analysis examined the factors affecting China's agricultural economic growth by developing a vector auto-regressive model (VAR), impulse response function (IRF) and variance decomposition function (VD). The results show that Chinese agriculture lacks long-term support factor. During the study period, an increase in the fixed asset investment, the total agricultural machinery power, the amount of chemical fertilizer used, and the education level of the rural labor force contributed to agricultural economic growth. However, an increase in the size of the agricultural labor force and in the total area under cultivation was not conducive to agricultural economic growth. In addition, China's agricultural economic growth was overly dependent on financial investment, while the contribution of other factors was relatively small. China's agricultural economy clearly has experienced extensive development. Hence, in the next development period, the Chinese government needs to increase agricultural fixed asset investment and strengthen its oversight. In addition, the government needs to strengthen its support of agricultural mechanization, set reasonable limits on the use of chemical fertilizers and, more importantly, focus on improvement in the quality of agricultural products and the accumulation of human capital.
{"title":"The Dynamic Analysis of China’s Agricultural Economic Growth","authors":"Wu Mingran, Zhao Min, Wu Zhaodan","doi":"10.11648/J.IJEEE.20190406.11","DOIUrl":"https://doi.org/10.11648/J.IJEEE.20190406.11","url":null,"abstract":"Based on time series data from 1990 to 2016, an empirical analysis examined the factors affecting China's agricultural economic growth by developing a vector auto-regressive model (VAR), impulse response function (IRF) and variance decomposition function (VD). The results show that Chinese agriculture lacks long-term support factor. During the study period, an increase in the fixed asset investment, the total agricultural machinery power, the amount of chemical fertilizer used, and the education level of the rural labor force contributed to agricultural economic growth. However, an increase in the size of the agricultural labor force and in the total area under cultivation was not conducive to agricultural economic growth. In addition, China's agricultural economic growth was overly dependent on financial investment, while the contribution of other factors was relatively small. China's agricultural economy clearly has experienced extensive development. Hence, in the next development period, the Chinese government needs to increase agricultural fixed asset investment and strengthen its oversight. In addition, the government needs to strengthen its support of agricultural mechanization, set reasonable limits on the use of chemical fertilizers and, more importantly, focus on improvement in the quality of agricultural products and the accumulation of human capital.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48040567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Photovoltaic (PV) system inverters usually operate at unitary power factor, injecting only active power into the system. Recently, many studies have been done analyzing potential benefits of reactive power provisioning, such as voltage regulation, congestion mitigation and loss reduction. This article analyzes possibilities for loss reduction in a typical medium voltage distribution system. Losses in the system are compared to the losses in the PV inverters. Different load conditions and PV penetration levels are considered and for each scenario various active power generation by PV inverters are taken into account, together with allowable levels of reactive power provisioning. As far as loss reduction is considered, there is very small number of PV inverters operating conditions for which positive energy balance exists. For low and medium load levels, there is no practical possibility for loss reduction. For high loading levels and higher PV penetration specific reactive savings, due to reactive power provisioning, increase and become bigger than additional losses in PV inverters, but for a very limited range of power factors.
{"title":"Reactive Power Compensation with PV Inverters for System Loss Reduction","authors":"S. Vlahinić, D. Franković, V. Komen, A. Antonić","doi":"10.3390/en12214062","DOIUrl":"https://doi.org/10.3390/en12214062","url":null,"abstract":"Photovoltaic (PV) system inverters usually operate at unitary power factor, injecting only active power into the system. Recently, many studies have been done analyzing potential benefits of reactive power provisioning, such as voltage regulation, congestion mitigation and loss reduction. This article analyzes possibilities for loss reduction in a typical medium voltage distribution system. Losses in the system are compared to the losses in the PV inverters. Different load conditions and PV penetration levels are considered and for each scenario various active power generation by PV inverters are taken into account, together with allowable levels of reactive power provisioning. As far as loss reduction is considered, there is very small number of PV inverters operating conditions for which positive energy balance exists. For low and medium load levels, there is no practical possibility for loss reduction. For high loading levels and higher PV penetration specific reactive savings, due to reactive power provisioning, increase and become bigger than additional losses in PV inverters, but for a very limited range of power factors.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2019-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3390/en12214062","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46694120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-21DOI: 10.11648/J.IJEEE.20190405.12
B. Chaka, A. Osano, J. Maghanga, M. Magu
Radicalization in waste-to-energy systems are on the rise to meet human energy demands. Biogas generation from kitchen wastes is one such scheme, though affected by poor yields and methane levels at low temperatures. In this research, biocatalytic extracts with fermentative properties were hereby assessed on their potential to fasten these processes and increase the biogas yield at ambient temperatures. The variations in kitchen waste substrate anaerobic parameters and elemental composition as well as biogas yields and methane levels were monitored in a 28-day retention period. Three 40-liter batch and unstirred bio-digesters containing biocatalysts Terminalia b., Acanthaceae spp. and a control setup were used. The results indicated rapid saccharification rates in the samples with additives. Terminalia b. additives exhibited high volatile solids hydrolysis rate of 98.3% followed by Acanthaceae spp. (50.8%) and control sample (29.4%). Similar trends were observed in organic carbon reduction as the levels of nitrogen, phosphorus and sulfur linearly increased. The biocatalysts did not affect substrate pH, volatile fatty acids and alkalinity levels. Terminalia b. sample produced 2.32 folds higher while Acanthaceae spp. sample produced 1.375 folds higher than the control sample. Terminalia b. methane levels were highest (45.475±0.922%) followed by the control sample (41.750±1.401) and Acanthaceae spp. sample (39.275±0.263%) after 28-day retention period at 19.5±0.5°C. Use of these biocatalysts in biofuel synthesis can thus optimize biogas production leading to greener economies.
{"title":"The Influence of Biocatalytic Plant Extracts on Biogas Production from Kitchen Wastes at Cryo-mesophilic Temperature Regimes","authors":"B. Chaka, A. Osano, J. Maghanga, M. Magu","doi":"10.11648/J.IJEEE.20190405.12","DOIUrl":"https://doi.org/10.11648/J.IJEEE.20190405.12","url":null,"abstract":"Radicalization in waste-to-energy systems are on the rise to meet human energy demands. Biogas generation from kitchen wastes is one such scheme, though affected by poor yields and methane levels at low temperatures. In this research, biocatalytic extracts with fermentative properties were hereby assessed on their potential to fasten these processes and increase the biogas yield at ambient temperatures. The variations in kitchen waste substrate anaerobic parameters and elemental composition as well as biogas yields and methane levels were monitored in a 28-day retention period. Three 40-liter batch and unstirred bio-digesters containing biocatalysts Terminalia b., Acanthaceae spp. and a control setup were used. The results indicated rapid saccharification rates in the samples with additives. Terminalia b. additives exhibited high volatile solids hydrolysis rate of 98.3% followed by Acanthaceae spp. (50.8%) and control sample (29.4%). Similar trends were observed in organic carbon reduction as the levels of nitrogen, phosphorus and sulfur linearly increased. The biocatalysts did not affect substrate pH, volatile fatty acids and alkalinity levels. Terminalia b. sample produced 2.32 folds higher while Acanthaceae spp. sample produced 1.375 folds higher than the control sample. Terminalia b. methane levels were highest (45.475±0.922%) followed by the control sample (41.750±1.401) and Acanthaceae spp. sample (39.275±0.263%) after 28-day retention period at 19.5±0.5°C. Use of these biocatalysts in biofuel synthesis can thus optimize biogas production leading to greener economies.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2019-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43736207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The aim of this work was to explore the effects of variables on the heat of regeneration, the stripping efficiency, the stripping rate, the steam generation rate, and the stripping factor. The Taguchi method was used for the experimental design. The process variables were the CO2 loading (A), the reboiler temperature (B), the solvent flow rate (C), and the concentration of the solvent (monoethanolamine (MEA) + 2-amino-2-methyl-1-propanol (AMP)) (D), which each had three levels. The stripping efficiency (E), stripping rate ( m ˙ CO 2 ), stripping factor (β), and heat of regeneration (Q) were determined by the mass and energy balances under a steady-state condition. Using signal/noise (S/N) analysis, the sequence of importance of the parameters and the optimum conditions were obtained, and the optimum operating conditions were further validated. The results showed that E was in the range of 20.98–55.69%; m ˙ CO 2 was in the range of 5.57 × 10−5–4.03 × 10−4 kg/s, and Q was in the range of 5.52–18.94 GJ/t. In addition, the S/N ratio analysis showed that the parameter sequence of importance as a whole was A > B > D > C, while the optimum conditions were A3B3C1D1, A3B3C3D2, and A3B2C2D2, for E, m ˙ CO 2 , and Q, respectively. Verifications were also performed and were found to satisfy the optimum conditions. Finally, the correlation equations that were obtained were discussed and an operating policy was discovered.
{"title":"Optimization in the Stripping Process of CO2 Gas Using Mixed Amines","authors":"P. Chen, Yanyin Lai","doi":"10.3390/EN12112202","DOIUrl":"https://doi.org/10.3390/EN12112202","url":null,"abstract":"The aim of this work was to explore the effects of variables on the heat of regeneration, the stripping efficiency, the stripping rate, the steam generation rate, and the stripping factor. The Taguchi method was used for the experimental design. The process variables were the CO2 loading (A), the reboiler temperature (B), the solvent flow rate (C), and the concentration of the solvent (monoethanolamine (MEA) + 2-amino-2-methyl-1-propanol (AMP)) (D), which each had three levels. The stripping efficiency (E), stripping rate ( m ˙ CO 2 ), stripping factor (β), and heat of regeneration (Q) were determined by the mass and energy balances under a steady-state condition. Using signal/noise (S/N) analysis, the sequence of importance of the parameters and the optimum conditions were obtained, and the optimum operating conditions were further validated. The results showed that E was in the range of 20.98–55.69%; m ˙ CO 2 was in the range of 5.57 × 10−5–4.03 × 10−4 kg/s, and Q was in the range of 5.52–18.94 GJ/t. In addition, the S/N ratio analysis showed that the parameter sequence of importance as a whole was A > B > D > C, while the optimum conditions were A3B3C1D1, A3B3C3D2, and A3B2C2D2, for E, m ˙ CO 2 , and Q, respectively. Verifications were also performed and were found to satisfy the optimum conditions. Finally, the correlation equations that were obtained were discussed and an operating policy was discovered.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2019-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3390/EN12112202","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44839469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a novel method of hydro power plant operation, based on the control of the injectors’ or wicked gates opening time as a function of the upper reservoir level. In this way, a faster power injection, depending on the current water level on the upper reservoir, could be achieved. When this level is higher, the opening time could be shorter; hence, hydropower ramps could be steeper. Due to this control, frequency excursions and load shedding trips are smaller, thus the power quality is enhanced. This method has been tested and validated by computer simulations in a case study located in El Hierro island, Canary Archipelago (Spain). The simulations made show significant improvements, dependent on upper reservoir water level, in power quality.
{"title":"Hydropower Plants Frequency Regulation Depending on Upper Reservoir Water Level","authors":"Platero, Sánchez, Nicolet, Allenbach","doi":"10.3390/EN12091637","DOIUrl":"https://doi.org/10.3390/EN12091637","url":null,"abstract":"This paper presents a novel method of hydro power plant operation, based on the control of the injectors’ or wicked gates opening time as a function of the upper reservoir level. In this way, a faster power injection, depending on the current water level on the upper reservoir, could be achieved. When this level is higher, the opening time could be shorter; hence, hydropower ramps could be steeper. Due to this control, frequency excursions and load shedding trips are smaller, thus the power quality is enhanced. This method has been tested and validated by computer simulations in a case study located in El Hierro island, Canary Archipelago (Spain). The simulations made show significant improvements, dependent on upper reservoir water level, in power quality.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2019-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3390/EN12091637","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43560499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The PV hosting capacity of low voltage feeders is restricted by voltage and current limits, and in many cases, voltage limit violations are the limiting factor for photovoltaic integration. To control the voltage, local Volt/var control strategies absorb or inject reactive power, provoking an additional current. This study analyzes the hosting capacity increase potential and the associated additional grid losses of local cosφ(P)- and Q(U)-control of photovoltaic inverters, and of local L(U)-control of inductive devices and its combination with Q-Autarkic prosumers. Therefore, four theoretical and one real low voltage test-feeders with distinct structures are considered: long overhead line, short overhead line, long cable, short cable and branched cable. While the theoretical test-feeders host homogeneously distributed PV-plants, the real one hosts heterogeneously distributed PV-plants. Each test-feeder is used to conduct load flow simulations in the presence of no-control and the different control strategies separately, while gradually increasing the PV-penetration. The minimum PV-penetration that provokes voltage or current limit violations is compared for the different control strategies and test-feeders. Simulation results of the theoretical test-feeders show that the hosting capacity increase potential of all local Volt/var control strategies is higher for the overhead line feeders than for the cable ones. Local L(U)-control, especially its combination with Q-Autarkic prosumers, increases the hosting capacity of all low voltage test-feeders significantly. The PV-inverter-based local Volt/var control strategies, i.e., Q(U)- and cosφ(P)-control, enable lower hosting capacity increases; in particular, cosφ(P)-control causes high additional currents, allowing the feeder to host only a relatively small PV-module rating per prosumer. Q(U)- and cosφ(P)-control are not sufficient to increase the hosting capacity of the long cable feeder significantly; they provoke high additional grid losses for the overhead line test-feeders. Meanwhile, L(U)-control, especially its combination with Q-Autarkic prosumers, increases the hosting capacity of the long cable feeder significantly, causing high additional grid losses during peak production of PV-plants. Regarding the real test-feeder with heterogeneously distributed PV-plants, on the one hand, the same trend concerning the HC increase prevails for the real branched cable test-feeder as for the theoretical short cable one. On the other hand, higher losses occur for the branched feeder in the case of L(U)-control and its combination with Q-Autarkic prosumers, due to the lower voltage set-points that have to be used for the inductive devices. All in all, the use of local L(U)-control, whether combined with Q-Autarkic prosumers or not, enables the effective and complete utilization of the existing radial low voltage feeders.
{"title":"Comparison of Local Volt/var Control Strategies for PV Hosting Capacity Enhancement of Low Voltage Feeders","authors":"D. Schultis","doi":"10.3390/EN12081560","DOIUrl":"https://doi.org/10.3390/EN12081560","url":null,"abstract":"The PV hosting capacity of low voltage feeders is restricted by voltage and current limits, and in many cases, voltage limit violations are the limiting factor for photovoltaic integration. To control the voltage, local Volt/var control strategies absorb or inject reactive power, provoking an additional current. This study analyzes the hosting capacity increase potential and the associated additional grid losses of local cosφ(P)- and Q(U)-control of photovoltaic inverters, and of local L(U)-control of inductive devices and its combination with Q-Autarkic prosumers. Therefore, four theoretical and one real low voltage test-feeders with distinct structures are considered: long overhead line, short overhead line, long cable, short cable and branched cable. While the theoretical test-feeders host homogeneously distributed PV-plants, the real one hosts heterogeneously distributed PV-plants. Each test-feeder is used to conduct load flow simulations in the presence of no-control and the different control strategies separately, while gradually increasing the PV-penetration. The minimum PV-penetration that provokes voltage or current limit violations is compared for the different control strategies and test-feeders. Simulation results of the theoretical test-feeders show that the hosting capacity increase potential of all local Volt/var control strategies is higher for the overhead line feeders than for the cable ones. Local L(U)-control, especially its combination with Q-Autarkic prosumers, increases the hosting capacity of all low voltage test-feeders significantly. The PV-inverter-based local Volt/var control strategies, i.e., Q(U)- and cosφ(P)-control, enable lower hosting capacity increases; in particular, cosφ(P)-control causes high additional currents, allowing the feeder to host only a relatively small PV-module rating per prosumer. Q(U)- and cosφ(P)-control are not sufficient to increase the hosting capacity of the long cable feeder significantly; they provoke high additional grid losses for the overhead line test-feeders. Meanwhile, L(U)-control, especially its combination with Q-Autarkic prosumers, increases the hosting capacity of the long cable feeder significantly, causing high additional grid losses during peak production of PV-plants. Regarding the real test-feeder with heterogeneously distributed PV-plants, on the one hand, the same trend concerning the HC increase prevails for the real branched cable test-feeder as for the theoretical short cable one. On the other hand, higher losses occur for the branched feeder in the case of L(U)-control and its combination with Q-Autarkic prosumers, due to the lower voltage set-points that have to be used for the inductive devices. All in all, the use of local L(U)-control, whether combined with Q-Autarkic prosumers or not, enables the effective and complete utilization of the existing radial low voltage feeders.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2019-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3390/EN12081560","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44016324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiangyu Kong, Yuying Ma, Xin Zhao, Ye Li, Yongxing Teng
In view of the existing verification methods of electric meters, there are problems such as high maintenance cost, poor accuracy, and difficulty in full coverage, etc. Starting from the perspective of analyzing the large-scale measured data collected by user-side electric meters, an online estimation method for the operating error of electric meters was proposed, which uses the recursive least squares (RLS) and introduces a double-parameter method with dynamic forgetting factors λa and λb to track the meter parameters changes in real time. Firstly, the obtained measured data are preprocessed, and the abnormal data such as null data and light load data are eliminated by an appropriate clustering method, so as to screen out the measured data of the similar operational states of each user. Then equations relating the head electric meter in the substation and each users’ electric meter and line loss based on the law of conservation of electric energy are established. Afterwards, the recursive least squares algorithm with double-parameter is used to estimate the parameters of line loss and the electric meter error. Finally, the effects of double dynamic forgetting factors, double constant forgetting factors and single forgetting factor on the accuracy of estimated error of electric meter are discussed. Through the program-controlled load simulation system, the proposed method is verified with higher accuracy and practicality.
{"title":"A Recursive Least Squares Method with Double-Parameter for Online Estimation of Electric Meter Errors","authors":"Xiangyu Kong, Yuying Ma, Xin Zhao, Ye Li, Yongxing Teng","doi":"10.3390/EN12050805","DOIUrl":"https://doi.org/10.3390/EN12050805","url":null,"abstract":"In view of the existing verification methods of electric meters, there are problems such as high maintenance cost, poor accuracy, and difficulty in full coverage, etc. Starting from the perspective of analyzing the large-scale measured data collected by user-side electric meters, an online estimation method for the operating error of electric meters was proposed, which uses the recursive least squares (RLS) and introduces a double-parameter method with dynamic forgetting factors λa and λb to track the meter parameters changes in real time. Firstly, the obtained measured data are preprocessed, and the abnormal data such as null data and light load data are eliminated by an appropriate clustering method, so as to screen out the measured data of the similar operational states of each user. Then equations relating the head electric meter in the substation and each users’ electric meter and line loss based on the law of conservation of electric energy are established. Afterwards, the recursive least squares algorithm with double-parameter is used to estimate the parameters of line loss and the electric meter error. Finally, the effects of double dynamic forgetting factors, double constant forgetting factors and single forgetting factor on the accuracy of estimated error of electric meter are discussed. Through the program-controlled load simulation system, the proposed method is verified with higher accuracy and practicality.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2019-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3390/EN12050805","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46458209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Previous studies have suggested that the use of high-capacity transportation (HCT) can lead to low-carbon road-transportation in the forest industry. This study shows the impacts (in terms of energy efficiency) of a three-year adaptation process of transportation (2014–2016) towards HCT that took place in a synchronized transportation system (STS). The use of three transportation fleet-management control (TFMC) methods was analyzed in various road infrastructures. Energy-efficiency calculations were undertaken based on the HCT vehicles’ mass limits (64, 68 and 76 t). The use of 76 t vehicles increased energy efficiency by 13.4% and reduced CO2 emissions by 3.5% (to 49.6 g/tkm). In addition, the results show that the energy efficiency of the STS could be improved by a further 3.1%. In this respect, the proposed TFMC was used to adjust the STS towards vehicle-group transportation while meeting the road-class constraints of local wood supply chains. Forest-industry companies in Finland and abroad can use the tailored TFMC to optimize the STS in the near future and to achieve the energy-efficient STS and the regulations of the European Commission in wood-procurement logistics.
{"title":"Improving Energy Efficiency in a Synchronized Road-Transportation System by Using a TFMC (Transportation Fleet-Management Control) in Finland","authors":"T. Palander, K. Kärhä","doi":"10.3390/EN12040670","DOIUrl":"https://doi.org/10.3390/EN12040670","url":null,"abstract":"Previous studies have suggested that the use of high-capacity transportation (HCT) can lead to low-carbon road-transportation in the forest industry. This study shows the impacts (in terms of energy efficiency) of a three-year adaptation process of transportation (2014–2016) towards HCT that took place in a synchronized transportation system (STS). The use of three transportation fleet-management control (TFMC) methods was analyzed in various road infrastructures. Energy-efficiency calculations were undertaken based on the HCT vehicles’ mass limits (64, 68 and 76 t). The use of 76 t vehicles increased energy efficiency by 13.4% and reduced CO2 emissions by 3.5% (to 49.6 g/tkm). In addition, the results show that the energy efficiency of the STS could be improved by a further 3.1%. In this respect, the proposed TFMC was used to adjust the STS towards vehicle-group transportation while meeting the road-class constraints of local wood supply chains. Forest-industry companies in Finland and abroad can use the tailored TFMC to optimize the STS in the near future and to achieve the energy-efficient STS and the regulations of the European Commission in wood-procurement logistics.","PeriodicalId":29914,"journal":{"name":"Advances in Energy Research","volume":"233 ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2019-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3390/EN12040670","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41314954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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