Reconfiguration,as well as optimal utilization of distributed generation sources and capacitor banks,are highly effective methods for reducing losses and improving the voltage profile,or in other words,the power quali...Reconfiguration,as well as optimal utilization of distributed generation sources and capacitor banks,are highly effective methods for reducing losses and improving the voltage profile,or in other words,the power quality in the power distribution system.Researchers have considered the use of distributed generation resources in recent years.There are numerous advantages to utilizing these resources,the most significant of which are the reduction of network losses and enhancement of voltage stability.Non-dominated Sorting Genetic Algorithm II(NSGA-II),Multi-Objective Particle Swarm Optimization(MOPSO),and Intersect Mutation Differential Evolution(IMDE)algorithms are used in this paper to perform optimal reconfiguration,simultaneous location,and capacity determination of distributed generation resources and capacitor banks.Three scenarios were used to replicate the studies.The reconfiguration of the switches,as well as the location and determination of the capacitor bank’s optimal capacity,were investigated in this scenario.However,in the third scenario,reconfiguration,and determining the location and capacity of the Distributed Generation(DG)resources and capacitor banks have been carried out simultaneously.Finally,the simulation results of these three algorithms are compared.The results indicate that the proposed NSGAII algorithm outperformed the other two multi-objective algorithms and was capable of maintaining smaller objective functions in all scenarios.Specifically,the energy losses were reduced from 211 to 51.35 kW(a 75.66%reduction),119.13 kW(a 43.54%reduction),and 23.13 kW(an 89.04%reduction),while the voltage stability index(VSI)decreased from 6.96 to 2.105,1.239,and 1.257,respectively,demonstrating significant improvement in the voltage profile.展开更多
The distribution networks sometimes suffer from excessive losses and voltage violations in densely populated areas. The aim of the present study is to improve the performance of a distribution network by successively ...The distribution networks sometimes suffer from excessive losses and voltage violations in densely populated areas. The aim of the present study is to improve the performance of a distribution network by successively applying mono-capacitor positioning, multiple positioning and reconfiguration processes using GA-based algorithms implemented in a Matlab environment. From the diagnostic study of this network, it was observed that a minimum voltage of 0.90 pu induces a voltage deviation of 5.26%, followed by active and reactive losses of 425.08 kW and 435.09 kVAR, respectively. Single placement with the NSGAII resulted in the placement of a 3000 kVAR capacitor at node 128, which proved to be the invariably neuralgic point. Multiple placements resulted in a 21.55% reduction in losses and a 0.74% regression in voltage profile performance. After topology optimization, the loss profile improved by 65.08% and the voltage profile improved by 1.05%. Genetic algorithms are efficient and effective tools for improving the performance of distribution networks, whose degradation is often dynamic due to the natural variability of loads.展开更多
With the development of power systems,a large number of shunt capacitors are used to improve power quality in the distribution network.The shunt capacitor banks are operated much frequently,as a result,the capacitor b...With the development of power systems,a large number of shunt capacitors are used to improve power quality in the distribution network.The shunt capacitor banks are operated much frequently,as a result,the capacitor banks will bear large numbers of over-voltage inevitably.If the over-voltage exceeds certain amplitude,the capacitor will be damaged.This paper aims at the capacitor banks in the 35 kV side of Shanghai Xu-xing 500 kV substation,and applies ATP-EMTP to simulate the over-voltages generated by operating the switches under different angles of the source.Finally,according to the results of simulation and theoretical analysis,a best choice(i.e.angles of the source) to switch on capacitor banks is proposed.In this case the over-voltage on the capacitor will be limited to lowest.展开更多
The main purpose of the electrical power system is to transport and distribute energy generated by the central power plants in a safe and reliable manner to the customer premises. Most of the electrical equipment is e...The main purpose of the electrical power system is to transport and distribute energy generated by the central power plants in a safe and reliable manner to the customer premises. Most of the electrical equipment is exposed within the open which suggests they can be vulnerable to lightning strikes, road dwindling, windstorms, and a few engineering activities with the potential of causing different degrees of damage to the electrical equipment. One of the ways to guard the equipment is to deploy switching devices. However, the operations of most of these switching devices produce oscillatory transient in the electrical transmission and distribution systems which result in voltage, current, and frequency fluctuations in the load. This paper investigates the effect of switching devices on power quality and proposes a positive sequence voltage power transient suppression technique that can spontaneously improve the distorted voltage at the instant of capacitor switching using the capacitor line model as a case study. MATLAB/Simulink software was utilized for the analysis on an electrical network model with bus voltages of 69 kV/12.47 kV and 480 V. The results showed that, during switching operations, the positive sequence voltage power detector block produces ripple-free accurate results.展开更多
Nowadays the optimal allocation of distributed generation (DG) in the distribution network becomes the popular research area in restructuring of power system. The capacitor banks introduced in the distribution network...Nowadays the optimal allocation of distributed generation (DG) in the distribution network becomes the popular research area in restructuring of power system. The capacitor banks introduced in the distribution networks for reactive power compensation also have the capacity to minimize the real and reactive power losses occurred in the system. Hence, this research integrates the allocation of renewable energy DG and capacitor banks in the radial distribution network to minimize the real power loss occurred in the system. A two-stage methodology is used for simultaneous allocation of renewable DG and capacitor banks. The optimum location of renewable energy DG and capacitor banks is determined using the distributed generation sitting index (DGSI) ranking method and the optimum sizing of DG and capacitor banks is found out for simultaneous placement using weight improved particle swarm optimization algorithm (WIPSO) and self adaptive differential evolution algorithm (SADE). This two-stage methodology reduces the burden of SADE and WIPSO algorithm, by using the DGSI index in determining the optimal location. Hence the computational time gets reduced which makes them suitable for online applications. By using the above methodology, a comprehensive performance analysis is done on IEEE 33 bus and 69 bus RDNs and the results are discussed in detail.展开更多
The purpose of the paper is to develop a solution for application of PV （photovoltaic） generators in MV （medium voltage） distribution system without unacceptable voltage changes due to drops of PV power output. Th...The purpose of the paper is to develop a solution for application of PV （photovoltaic） generators in MV （medium voltage） distribution system without unacceptable voltage changes due to drops of PV power output. The proposed solution includes operation of PV with predetermined leading power factor and addition of a capacitor bank in parallel to PV plant in order to compensate the reactive power absorbed by the PV inverters. The analytical expression of required power factor angle is derived. Adding a capacitor bank in parallel to PV power plant may pose a problem because of space limitations. The dimensions and cost of small MV capacitor banks depend significantly on the capacitor bank protection against internal faults. Application of the developed negative-sequence current difference method for the unbalance protection of the capacitor banks enables to achieve a compact and cost-reduced design of the banks connected in parallel to PV power plants. A real-world example of operation of the PV plant in parallel to the capacitor bank with the novel protection scheme is described.展开更多
以提升电网供电质量为目的,设计基于多时间尺度的风电场无功补偿装置协调控制方法。风电场功率预测模块利用神经网络预测风电功率,并将预测结果传输至电网调度模块与无功补偿装置协调控制模块;电网调度模块依据风电功率预测结果,设置未...以提升电网供电质量为目的,设计基于多时间尺度的风电场无功补偿装置协调控制方法。风电场功率预测模块利用神经网络预测风电功率,并将预测结果传输至电网调度模块与无功补偿装置协调控制模块;电网调度模块依据风电功率预测结果,设置未来风电场的无功电压控制计划并传输至无功补偿装置协调控制模块;无功补偿装置协调控制模块,依据风电功率预测结果以及无功电压控制计划,从日内与日前两个时间尺度构建无功电压优化控制模型,从日前时间尺度(20 min),利用电容/电抗器组等大幅控制风电场无功电压,从日内时间尺度(15 ms),利用静止无功补偿器(static var compensator,SVC)补偿无功电压小幅波动。实验结果显示,该方法控制下,风电场无功储量提升,母线电压的稳定性与输出质量显著提升。展开更多
Verification of operation parameters of VVER-1200 NPP Simulator installed at Nuclear Training Center, VINATOM has been performed. This simulator has been supplied for Vietnam in the framework of IAEA TC Project VIE201...Verification of operation parameters of VVER-1200 NPP Simulator installed at Nuclear Training Center, VINATOM has been performed. This simulator has been supplied for Vietnam in the framework of IAEA TC Project VIE2010 on Developing Nuclear Power Infrastructure—Phase II hosted by the Vietnam Atomic Energy Agency (VAEA). The comparison of the main parameters in nominal power operation with design data given in safety analysis report of VVER-1200/V392M as well as Ninh Thuan FSSAR is presented. In this study, the reactor coolant coast-down transient is investigated using the VVER-1200 NPP simulator. The simulated results performed in the simulator through switching off one reactor coolant pump in comparisons with experiment results performed in VVER-1000 reactor are given. The similarity between the measured and simulated results shows that the thermal hydraulic characteristics and the control protection systems are modeled in a reasonable way. A good agreement in operating parameters was found between the VVER-1200 NPP simulator and VVER-1200/V392M’s PSAR.展开更多
In distribution systems,network reconfiguration and capacitor placement are commonly used to diminish power losses and keep voltage profiles within acceptable limits.Moreover,the problem of DG allocation and sizing is...In distribution systems,network reconfiguration and capacitor placement are commonly used to diminish power losses and keep voltage profiles within acceptable limits.Moreover,the problem of DG allocation and sizing is great important.In this work,a combination of a fuzzy multi-objective approach and bacterial foraging optimization(BFO) as a meta-heuristic algorithm is used to solve the simultaneous reconfiguration and optimal sizing of DGs and shunt capacitors in a distribution system.Each objective is transferred into fuzzy domain using its membership function.Then,the overall fuzzy satisfaction function is formed and considered a fitness function inasmuch as the value of this function has to be maximized to gain the optimal solution.The numerical results show that the presented algorithm improves the performance much more than other meta-heuristic algorithms.Simulation results found that simultaneous reconfiguration with DG and shunt capacitors allocation(case 5) has 77.41%,42.15%,and 56.14%improvements in power loss reduction,load balancing,and voltage profile indices,respectively in 33-bus test system.This result found 87.27%,35.82%,and 54.34%improvements of mentioned indices respectively for 69-bus system.展开更多
文摘Reconfiguration,as well as optimal utilization of distributed generation sources and capacitor banks,are highly effective methods for reducing losses and improving the voltage profile,or in other words,the power quality in the power distribution system.Researchers have considered the use of distributed generation resources in recent years.There are numerous advantages to utilizing these resources,the most significant of which are the reduction of network losses and enhancement of voltage stability.Non-dominated Sorting Genetic Algorithm II(NSGA-II),Multi-Objective Particle Swarm Optimization(MOPSO),and Intersect Mutation Differential Evolution(IMDE)algorithms are used in this paper to perform optimal reconfiguration,simultaneous location,and capacity determination of distributed generation resources and capacitor banks.Three scenarios were used to replicate the studies.The reconfiguration of the switches,as well as the location and determination of the capacitor bank’s optimal capacity,were investigated in this scenario.However,in the third scenario,reconfiguration,and determining the location and capacity of the Distributed Generation(DG)resources and capacitor banks have been carried out simultaneously.Finally,the simulation results of these three algorithms are compared.The results indicate that the proposed NSGAII algorithm outperformed the other two multi-objective algorithms and was capable of maintaining smaller objective functions in all scenarios.Specifically,the energy losses were reduced from 211 to 51.35 kW(a 75.66%reduction),119.13 kW(a 43.54%reduction),and 23.13 kW(an 89.04%reduction),while the voltage stability index(VSI)decreased from 6.96 to 2.105,1.239,and 1.257,respectively,demonstrating significant improvement in the voltage profile.
文摘The distribution networks sometimes suffer from excessive losses and voltage violations in densely populated areas. The aim of the present study is to improve the performance of a distribution network by successively applying mono-capacitor positioning, multiple positioning and reconfiguration processes using GA-based algorithms implemented in a Matlab environment. From the diagnostic study of this network, it was observed that a minimum voltage of 0.90 pu induces a voltage deviation of 5.26%, followed by active and reactive losses of 425.08 kW and 435.09 kVAR, respectively. Single placement with the NSGAII resulted in the placement of a 3000 kVAR capacitor at node 128, which proved to be the invariably neuralgic point. Multiple placements resulted in a 21.55% reduction in losses and a 0.74% regression in voltage profile performance. After topology optimization, the loss profile improved by 65.08% and the voltage profile improved by 1.05%. Genetic algorithms are efficient and effective tools for improving the performance of distribution networks, whose degradation is often dynamic due to the natural variability of loads.
基金supported of the Fundamental Research Founds for the Central Universities
文摘With the development of power systems,a large number of shunt capacitors are used to improve power quality in the distribution network.The shunt capacitor banks are operated much frequently,as a result,the capacitor banks will bear large numbers of over-voltage inevitably.If the over-voltage exceeds certain amplitude,the capacitor will be damaged.This paper aims at the capacitor banks in the 35 kV side of Shanghai Xu-xing 500 kV substation,and applies ATP-EMTP to simulate the over-voltages generated by operating the switches under different angles of the source.Finally,according to the results of simulation and theoretical analysis,a best choice(i.e.angles of the source) to switch on capacitor banks is proposed.In this case the over-voltage on the capacitor will be limited to lowest.
文摘The main purpose of the electrical power system is to transport and distribute energy generated by the central power plants in a safe and reliable manner to the customer premises. Most of the electrical equipment is exposed within the open which suggests they can be vulnerable to lightning strikes, road dwindling, windstorms, and a few engineering activities with the potential of causing different degrees of damage to the electrical equipment. One of the ways to guard the equipment is to deploy switching devices. However, the operations of most of these switching devices produce oscillatory transient in the electrical transmission and distribution systems which result in voltage, current, and frequency fluctuations in the load. This paper investigates the effect of switching devices on power quality and proposes a positive sequence voltage power transient suppression technique that can spontaneously improve the distorted voltage at the instant of capacitor switching using the capacitor line model as a case study. MATLAB/Simulink software was utilized for the analysis on an electrical network model with bus voltages of 69 kV/12.47 kV and 480 V. The results showed that, during switching operations, the positive sequence voltage power detector block produces ripple-free accurate results.
文摘Nowadays the optimal allocation of distributed generation (DG) in the distribution network becomes the popular research area in restructuring of power system. The capacitor banks introduced in the distribution networks for reactive power compensation also have the capacity to minimize the real and reactive power losses occurred in the system. Hence, this research integrates the allocation of renewable energy DG and capacitor banks in the radial distribution network to minimize the real power loss occurred in the system. A two-stage methodology is used for simultaneous allocation of renewable DG and capacitor banks. The optimum location of renewable energy DG and capacitor banks is determined using the distributed generation sitting index (DGSI) ranking method and the optimum sizing of DG and capacitor banks is found out for simultaneous placement using weight improved particle swarm optimization algorithm (WIPSO) and self adaptive differential evolution algorithm (SADE). This two-stage methodology reduces the burden of SADE and WIPSO algorithm, by using the DGSI index in determining the optimal location. Hence the computational time gets reduced which makes them suitable for online applications. By using the above methodology, a comprehensive performance analysis is done on IEEE 33 bus and 69 bus RDNs and the results are discussed in detail.
文摘The purpose of the paper is to develop a solution for application of PV （photovoltaic） generators in MV （medium voltage） distribution system without unacceptable voltage changes due to drops of PV power output. The proposed solution includes operation of PV with predetermined leading power factor and addition of a capacitor bank in parallel to PV plant in order to compensate the reactive power absorbed by the PV inverters. The analytical expression of required power factor angle is derived. Adding a capacitor bank in parallel to PV power plant may pose a problem because of space limitations. The dimensions and cost of small MV capacitor banks depend significantly on the capacitor bank protection against internal faults. Application of the developed negative-sequence current difference method for the unbalance protection of the capacitor banks enables to achieve a compact and cost-reduced design of the banks connected in parallel to PV power plants. A real-world example of operation of the PV plant in parallel to the capacitor bank with the novel protection scheme is described.
文摘以提升电网供电质量为目的,设计基于多时间尺度的风电场无功补偿装置协调控制方法。风电场功率预测模块利用神经网络预测风电功率,并将预测结果传输至电网调度模块与无功补偿装置协调控制模块;电网调度模块依据风电功率预测结果,设置未来风电场的无功电压控制计划并传输至无功补偿装置协调控制模块;无功补偿装置协调控制模块,依据风电功率预测结果以及无功电压控制计划,从日内与日前两个时间尺度构建无功电压优化控制模型,从日前时间尺度(20 min),利用电容/电抗器组等大幅控制风电场无功电压,从日内时间尺度(15 ms),利用静止无功补偿器(static var compensator,SVC)补偿无功电压小幅波动。实验结果显示,该方法控制下,风电场无功储量提升,母线电压的稳定性与输出质量显著提升。
文摘Verification of operation parameters of VVER-1200 NPP Simulator installed at Nuclear Training Center, VINATOM has been performed. This simulator has been supplied for Vietnam in the framework of IAEA TC Project VIE2010 on Developing Nuclear Power Infrastructure—Phase II hosted by the Vietnam Atomic Energy Agency (VAEA). The comparison of the main parameters in nominal power operation with design data given in safety analysis report of VVER-1200/V392M as well as Ninh Thuan FSSAR is presented. In this study, the reactor coolant coast-down transient is investigated using the VVER-1200 NPP simulator. The simulated results performed in the simulator through switching off one reactor coolant pump in comparisons with experiment results performed in VVER-1000 reactor are given. The similarity between the measured and simulated results shows that the thermal hydraulic characteristics and the control protection systems are modeled in a reasonable way. A good agreement in operating parameters was found between the VVER-1200 NPP simulator and VVER-1200/V392M’s PSAR.
文摘In distribution systems,network reconfiguration and capacitor placement are commonly used to diminish power losses and keep voltage profiles within acceptable limits.Moreover,the problem of DG allocation and sizing is great important.In this work,a combination of a fuzzy multi-objective approach and bacterial foraging optimization(BFO) as a meta-heuristic algorithm is used to solve the simultaneous reconfiguration and optimal sizing of DGs and shunt capacitors in a distribution system.Each objective is transferred into fuzzy domain using its membership function.Then,the overall fuzzy satisfaction function is formed and considered a fitness function inasmuch as the value of this function has to be maximized to gain the optimal solution.The numerical results show that the presented algorithm improves the performance much more than other meta-heuristic algorithms.Simulation results found that simultaneous reconfiguration with DG and shunt capacitors allocation(case 5) has 77.41%,42.15%,and 56.14%improvements in power loss reduction,load balancing,and voltage profile indices,respectively in 33-bus test system.This result found 87.27%,35.82%,and 54.34%improvements of mentioned indices respectively for 69-bus system.
