scholarly journals Load Transfer Device for Solving a Three-Phase Unbalance Problem Under a Low-Voltage Distribution Network

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2842 ◽  
Author(s):  
Guanghai Bao ◽  
Sikai Ke

In the low-voltage (LV) distribution network, a three-phase unbalance problem often exists. It does not only increase line loss but also threaten the safety of the distribution network. Therefore, the author designs a residential load transfer device for a LV distribution network that can deal with a three-phase unbalance problem by changing the connecting phase of the load. It consists of three parts: user controller for phase swapping, central controller for signal processing and monitoring platform for strategy calculation. This design was based on message queuing telemetry transport (MQTT) communication protocol, and Long Range and 4th Generation mobile telecommunications (LoRa + 4G) communication mode is used to realize the wireless connection between equipment and monitoring platform, and a control scheme is proposed. The improved multi-population genetic algorithm (IMPGA) with multi-objective is used to find the optimal swapping strategy, which is implemented on the monitoring platform. Then the phase swapping is realized by remote control, and the function of reducing three-phase unbalance is realized. The practical experimental result shows that the method can help to reduce the three-phase unbalance rate by changing the connection phase of the load, and the simulation results verify the effectiveness of the algorithm in the phase-swapping strategy.

Author(s):  
Jing Zhang ◽  
Ming Jin ◽  
Yunguo Cheng ◽  
Dejun Wang ◽  
Kang Zhou ◽  
...  

2019 ◽  
Vol 118 ◽  
pp. 02071
Author(s):  
Meifang Wei ◽  
Jing Yang ◽  
Xuhua Zeng ◽  
Haiyan Wu ◽  
Di Huang

For the power distribution network line loss calculation, there are some problems, such as backward method, long calculation period, large workload and poor real-time performance. To this end, this paper proposes a real-time calculation method for distribution line loss based on dynamic three-phase unbalance, and a hardware device system with unbalanced phase sequence identification function, three-phase unbalance detection function and line loss real-time calculation function has been developed. The system uses a master-slave design based on the principle of wireless transmission. The slave collects standard three-phase current signals and transmits them to the host through wireless transmission. The host is installed on the low voltage side of the transformer in the transformer region, and the current signal of the transformer region is collected in real time. Unbalanced phase sequence identification, unbalance calculation, and line loss calculation based on dynamic unbalance are performed by comparing the current signals collected by the master and the slave. The above algorithm implementation process can be displayed online in real time. In addition to the core data processing and waveform display functions, the device also includes a battery power supply and management system, a signal storage and transmission system, and temperature measurement, and overcurrent and overvoltage protection. The test results of the device show that the device has the characteristics of convenient carrying, fast detection of three-phase unbalance, and accurate calculation of line loss. The device can monitor the running status of the distribution network transformer region in real time.


2014 ◽  
Vol 1008-1009 ◽  
pp. 417-420 ◽  
Author(s):  
Xiao Hui Liu ◽  
Lin Ma ◽  
Yun Song Shi ◽  
Yu Jiang Wang ◽  
Jun Hua Li

Aiming at the insufficiency of Equivalent Resistance Method for a low-voltage distribution line loss calculation, this article has been improved. Then this paper presents the method of using three-phase quantity of electricity to calculate three-phase current, it can calculate the three-phase unbalanced line loss without current date and facilitate the application of Three-phase Unbalanced Method. It develops our own program based on Visio to calculate low-voltage distribution line loss. The results showed: Improved Equivalent Resistance Method improves the accuracy; in the three-phase unbalanced the method of using three-phase quantity of electricity to calculate three-phase current is more easily modified and more practical value.


Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2522 ◽  
Author(s):  
Mengting Yao ◽  
Yun Zhu ◽  
Junjie Li ◽  
Hua Wei ◽  
Penghui He

Line loss rate plays an essential role in evaluating the economic operation of power systems. However, in a low voltage (LV) distribution network, calculating line loss rate has become more cumbersome due to poor configuration of the measuring and detecting device, the difficulty in collecting operational data, and the excessive number of components and nodes. Most previous studies mainly focused on the approaches to calculate or predict line loss rate, but rarely involve the evaluation of the prediction results. In this paper, we propose an approach based on a gradient boosting decision tree (GBDT), to predict line loss rate. GBDT inherits the advantages of both statistical models and AI approaches, and can identify the complex and nonlinear relationship while computing the relative importance among variables. An empirical study on a data set in a city demonstrates that our proposed approach performs well in predicting line loss rate, given a large number of unlabeled examples. Experiments and analysis also confirmed the effectiveness of our proposed approach in anomaly detection and practical project management.


2012 ◽  
Vol 263-266 ◽  
pp. 649-654
Author(s):  
Yan Wei Zheng ◽  
Zhong Hai Bai ◽  
Zhi Quan Feng

To balance three-phase loads in distribution network with abundant of single-phase loads, the idea of three-phase adjustment and wiring method is proposed in this paper. Three-phase adjustment controller is designed, and the least load adjustment strategy is proposed, which can adjust the three-phase load to roughly balance automatically. The system can solve the serious three-phase unbalance problem of the lines with single-phase load, which may instead of capacitive compensation in low voltage distribution network. It can improve power quality and reduce network losses.


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