The unintentional islanding of micro-grid may cause negative impacts on distribution loads and distributed generations,so it must be detected within the acceptable duration.In this paper a new islanding detection algo...The unintentional islanding of micro-grid may cause negative impacts on distribution loads and distributed generations,so it must be detected within the acceptable duration.In this paper a new islanding detection algorithm is proposed.This algorithm introduces the frequency feedback method by the reactive power compensation to derive the frequency continuous shift. Accordingly,the islanding can be detected by monitoring the frequency within 0.1 s.The simulation results prove that this algorithm has extremely small non-detection zone,and meanwhile it presents an excellent islanding detection speed as well.展开更多
Micro-grids comprise low voltage distribution systems with distributed energy resources(DERs) and controllable loads which can operate connected to the medium voltage grid or islanded in a controlled coordinated way. ...Micro-grids comprise low voltage distribution systems with distributed energy resources(DERs) and controllable loads which can operate connected to the medium voltage grid or islanded in a controlled coordinated way. This concept aims to move from "connect and forget" philosophy towards a full integration of DERs. Micro-grids can provide numerous economic and environmental benefits for end-customers, utilities and society. However, their implementation poses great technical challenges, such as a new philosophy in design of protection systems. In this work, a micro-grid protection scheme is presented based on positive-sequence component using phasor measurement units(PMUs) and a central protection unit(CPU). The salient feature of the proposed scheme in comparison with the previous works is that it has the ability to protect both radial and looped micro-grids against different types of faults with the capability of single-phase tripping. Furthermore, since the CPU is capable of updating its pickup values(upstream and downstream equivalent positive-sequence impedances of each line) after the first change in the micro-grid configuration(such as transferring from grid-connected to islanded mode and or disconnection of a line, bus, or DER either in grid-connected mode or in islanded mode), it can protect micro-grid against subsequent faults. Finally, in order to verify the effectiveness of the suggested scheme and the CPU, several simulations have been undertaken by using DIg SILENT Power Factory and MATLAB software packages.展开更多
In many developing countries, there are regions where the electrical grid is weak or nonexistent. However, in these areas, large amounts of distributed energy sources, such as hydro, are often available and could be s...In many developing countries, there are regions where the electrical grid is weak or nonexistent. However, in these areas, large amounts of distributed energy sources, such as hydro, are often available and could be suitably exploited. To this aim, the low head hydro power plants can play a significant role. In fact, recent technological advances in mini-hydro turbines and decreasing costs of static electricity conversion devices enable to realize suitable power plants for an efficient and profitable exploitation of these sites. One of the major challenges is the integration of the above-mentioned power plants into autonomous electrical systems, islanded and/or disconnectable from the main distribution network. In this paper, an innovative control strategy for a low head hydro power plant supplying users in small clusters of villages is proposed.展开更多
在交直流混合微电网中,并联互联变流器(parallel bidirectional power converters,BPCs)可以实现大容量的功率传输,以满足新型电力系统在空间上的供需匹配。如何在占用更少资源的同时协调控制BPCs实现功率的比例共享,是交直流混合微电网...在交直流混合微电网中,并联互联变流器(parallel bidirectional power converters,BPCs)可以实现大容量的功率传输,以满足新型电力系统在空间上的供需匹配。如何在占用更少资源的同时协调控制BPCs实现功率的比例共享,是交直流混合微电网中BPCs控制的研究难点。因此,该文设计了一种针对BPCs的事件触发改进一致性协调控制策略。以归一化下垂控制为基础,提出了改进的比例功率一致性算法,实现BPCs间高精度比例功率共享。在此之上,基于BPCs比例功率误差建立事件触发改进一致性算法,并预设触发函数的预判阈值,从而降低系统在稳定状态下的通信次数。最后进行仿真对比分析,结果表明该文提出的方法相比基本一致性算法通信量减少98.35%;同时,与现有控制策略相比,该文提出的方法有着更好的控制性能。展开更多
基金National High-Tech R&D Program of China(No.2007AA05Z241).
文摘The unintentional islanding of micro-grid may cause negative impacts on distribution loads and distributed generations,so it must be detected within the acceptable duration.In this paper a new islanding detection algorithm is proposed.This algorithm introduces the frequency feedback method by the reactive power compensation to derive the frequency continuous shift. Accordingly,the islanding can be detected by monitoring the frequency within 0.1 s.The simulation results prove that this algorithm has extremely small non-detection zone,and meanwhile it presents an excellent islanding detection speed as well.
文摘Micro-grids comprise low voltage distribution systems with distributed energy resources(DERs) and controllable loads which can operate connected to the medium voltage grid or islanded in a controlled coordinated way. This concept aims to move from "connect and forget" philosophy towards a full integration of DERs. Micro-grids can provide numerous economic and environmental benefits for end-customers, utilities and society. However, their implementation poses great technical challenges, such as a new philosophy in design of protection systems. In this work, a micro-grid protection scheme is presented based on positive-sequence component using phasor measurement units(PMUs) and a central protection unit(CPU). The salient feature of the proposed scheme in comparison with the previous works is that it has the ability to protect both radial and looped micro-grids against different types of faults with the capability of single-phase tripping. Furthermore, since the CPU is capable of updating its pickup values(upstream and downstream equivalent positive-sequence impedances of each line) after the first change in the micro-grid configuration(such as transferring from grid-connected to islanded mode and or disconnection of a line, bus, or DER either in grid-connected mode or in islanded mode), it can protect micro-grid against subsequent faults. Finally, in order to verify the effectiveness of the suggested scheme and the CPU, several simulations have been undertaken by using DIg SILENT Power Factory and MATLAB software packages.
文摘In many developing countries, there are regions where the electrical grid is weak or nonexistent. However, in these areas, large amounts of distributed energy sources, such as hydro, are often available and could be suitably exploited. To this aim, the low head hydro power plants can play a significant role. In fact, recent technological advances in mini-hydro turbines and decreasing costs of static electricity conversion devices enable to realize suitable power plants for an efficient and profitable exploitation of these sites. One of the major challenges is the integration of the above-mentioned power plants into autonomous electrical systems, islanded and/or disconnectable from the main distribution network. In this paper, an innovative control strategy for a low head hydro power plant supplying users in small clusters of villages is proposed.
文摘在交直流混合微电网中,并联互联变流器(parallel bidirectional power converters,BPCs)可以实现大容量的功率传输,以满足新型电力系统在空间上的供需匹配。如何在占用更少资源的同时协调控制BPCs实现功率的比例共享,是交直流混合微电网中BPCs控制的研究难点。因此,该文设计了一种针对BPCs的事件触发改进一致性协调控制策略。以归一化下垂控制为基础,提出了改进的比例功率一致性算法,实现BPCs间高精度比例功率共享。在此之上,基于BPCs比例功率误差建立事件触发改进一致性算法,并预设触发函数的预判阈值,从而降低系统在稳定状态下的通信次数。最后进行仿真对比分析,结果表明该文提出的方法相比基本一致性算法通信量减少98.35%;同时,与现有控制策略相比,该文提出的方法有着更好的控制性能。
