An on-line tap-changing circuit was developed for use with low voltage transformers (10 kV/380 V, or equivalent), in which the tap positions could be set independently for each low voltage feeder. This allows for poss...An on-line tap-changing circuit was developed for use with low voltage transformers (10 kV/380 V, or equivalent), in which the tap positions could be set independently for each low voltage feeder. This allows for possible variation in loads and distributed generation between different feeders fed from a given transformer, allowing the line voltages to be kept within limits on all feeders. A combination of computer simulation and practical experiments was used. A model constructed in Excel gave preliminary results, which was used to specify a more detailed model in Matlab? Simulink. A small-scale 220/380 V distribution network was constructed, with currents limited to 5 A per phase. Finally, a rotary switch was constructed, suitable for currents up to 500 A, which would be required for a full-scale low voltage distribution network. The results showed that the voltage could be kept within limits, even with a large difference in load and distributed generation from one feeder to another.展开更多
In distribution systems,voltage levels of the various buses should be maintained within the permissible limits for satisfactory operation of all electrical installations and equipment.The task of voltage control is cl...In distribution systems,voltage levels of the various buses should be maintained within the permissible limits for satisfactory operation of all electrical installations and equipment.The task of voltage control is closely associated with fluctuating load conditions and corresponding requirements of reactive power compensation.The problem of load bus voltage optimization in distribution systems that have distributed generation(DG)has recently become an issue.In Oman,the distribution code limits the load bus voltage variations within±6%of the nominal value.Several voltage control methods are employed in active distribution systems with a high share of photovoltaic systems(PV)to keep the voltage levels within the desirable limits.In addition to the constraint of targeting the best voltage profile,another constraint has to be achieved which is the minimum loss in the distribution network.An optimised solution for voltage of load busses with on-load tap-changing(OLTC)tarnsformers and PV sources is presented in this paper.This study addresses the problem of optimizing the injected power from PV systems associated with the facilities of tap-changing transformers,as it is an important means of controlling voltage throughout the system.To avoid violating tap-changing constraints,a method is depicted for determining the minimal changes in transformer taps to control voltage levels with distributed PV sources.The taps of a range+5 to-15%,can be achieved by tap-changing transformers.The OLTC operation was designed to keep the secondary bus within the voltage standard for MV networks.展开更多
In this paper,a new type of automatic transmitter(AT)is proposed to properly adjust the voltage of the train without installing additional equipment.The proposed tap-changing AT is expected to raise the voltage betwee...In this paper,a new type of automatic transmitter(AT)is proposed to properly adjust the voltage of the train without installing additional equipment.The proposed tap-changing AT is expected to raise the voltage between catenary and rail by regulating the turn-ratio between primary and secondary winding according to catenary voltage and verified its effects through the multi ports network analysis technique modeling of it.Through the simulation and analysis of the electric railway systems,it is shown that it can secure the load capacity and solve the large voltage drop problem by raising the voltage across railway vehicles back to the normal voltage level.展开更多
文摘An on-line tap-changing circuit was developed for use with low voltage transformers (10 kV/380 V, or equivalent), in which the tap positions could be set independently for each low voltage feeder. This allows for possible variation in loads and distributed generation between different feeders fed from a given transformer, allowing the line voltages to be kept within limits on all feeders. A combination of computer simulation and practical experiments was used. A model constructed in Excel gave preliminary results, which was used to specify a more detailed model in Matlab? Simulink. A small-scale 220/380 V distribution network was constructed, with currents limited to 5 A per phase. Finally, a rotary switch was constructed, suitable for currents up to 500 A, which would be required for a full-scale low voltage distribution network. The results showed that the voltage could be kept within limits, even with a large difference in load and distributed generation from one feeder to another.
文摘In distribution systems,voltage levels of the various buses should be maintained within the permissible limits for satisfactory operation of all electrical installations and equipment.The task of voltage control is closely associated with fluctuating load conditions and corresponding requirements of reactive power compensation.The problem of load bus voltage optimization in distribution systems that have distributed generation(DG)has recently become an issue.In Oman,the distribution code limits the load bus voltage variations within±6%of the nominal value.Several voltage control methods are employed in active distribution systems with a high share of photovoltaic systems(PV)to keep the voltage levels within the desirable limits.In addition to the constraint of targeting the best voltage profile,another constraint has to be achieved which is the minimum loss in the distribution network.An optimised solution for voltage of load busses with on-load tap-changing(OLTC)tarnsformers and PV sources is presented in this paper.This study addresses the problem of optimizing the injected power from PV systems associated with the facilities of tap-changing transformers,as it is an important means of controlling voltage throughout the system.To avoid violating tap-changing constraints,a method is depicted for determining the minimal changes in transformer taps to control voltage levels with distributed PV sources.The taps of a range+5 to-15%,can be achieved by tap-changing transformers.The OLTC operation was designed to keep the secondary bus within the voltage standard for MV networks.
基金KETEP(Korea Institute of Energy Technology Evaluation and Planning)grant funded by the Korea government(MOTIE)(No.20191210301890)。
文摘In this paper,a new type of automatic transmitter(AT)is proposed to properly adjust the voltage of the train without installing additional equipment.The proposed tap-changing AT is expected to raise the voltage between catenary and rail by regulating the turn-ratio between primary and secondary winding according to catenary voltage and verified its effects through the multi ports network analysis technique modeling of it.Through the simulation and analysis of the electric railway systems,it is shown that it can secure the load capacity and solve the large voltage drop problem by raising the voltage across railway vehicles back to the normal voltage level.
文摘随着配电网中分布式光伏(distributed photovoltaic,DPV)大量并网,电压越限和电压波动越来越严重,考虑新型电能质量治理装置的电压无功优化协调控制方法需要进一步完善,以适应电网的新变化。该文考虑了新型柔性有载调压变压器(on-load tap changer,OLTC)的电能质量调节作用,提出一种两阶段电压无功优化协调控制方法,其中一阶段为日前小时级调度阶段,根据分布式光伏和负荷的预测数据,通过潮流计算和迭代优化,获取DPV的有功出力结果、柔性OLTC分接头和电容器组的投切结果;二阶段为分钟级无功优化阶段,在第一阶段的基础上,考虑柔性OLTC和DPV的无功出力特性,调节装备无功出力的同时修正第一阶段电容器组投切组合,进一步降低各个节点最大电压偏差,使配电网电压分布更合理。搭建了IEEE33节点配电系统仿真模型,所提出的考虑柔性OLTC的两阶段电压无功优化协调控制方法能够在常规经济性最优目标下的88.07%DPV消纳水平基础上提高9.29%,同时满足全节点全时段电压偏差小于0.1pu,综合经济性提高7.8%,结果证明了所提方法的合理性和有效性。
