Xu Hongwei

Research on the Influence of Load Characteristics of Distributed Power Grid on Electric Energy Metering

As a large number of Distributed Generation Connecting Electric Grid put into operation, there are many impacts on power metering of power grid due to the problems of large fluctuation of load and frequent reverse of power, injecting DC component and harmonic component into power grid, generating voltage deviation, voltage fluctuation and flicker, and voltage unbalance. Measurement accuracy of traditional metering devices is difficult to guarantee. Therefore, the adaptability of traditional metering devices in the distributed power grid environment and the improvement of new technical methods to the Distributed Generation Connecting Electric Grid need to be studied. In this paper, through the analysis of the field operation data, it is proposed that the load fluctuation and frequent reverse of power can be solved by using the bidirectional and wide-range metering gateway meter; by analyzing the influence of the secondary transformer on the DC component, it is proposed that the influence of the DC component on the power metering can be almost ignored under the 0.5% DC component injection of the Distributed Generation Connecting Electric Grid. By analyzing zero flux technology, phase matching technology and high frequency sampling technology, a method to solve the problem of synchronous sampling of voltage and current under the influence of harmonics is proposed. By analyzing the point product and harmonic algorithm, the sampling rate requirement of accurate measurement of electric energy is proposed. A series of reasonable technical means and requirements are put forward in this paper, which greatly improves the power metering problem under the Distributed Generation Connecting Electric Grid.

Preparing for the SKA: The Chinese perspectives

Since 1993, astronomers and engineers from more than 100 institutions in 20 different countries including China, have engaged in the international mega-science project—the Square Kilometre Array (SKA), which will be the world’s largest synthesis radio telescope. The SKA is currently in its pre-construction phase, and China has been playing a very active role. China has participated in 6 of the total of 10 SKA work packages, and carried out R&D in dish array, aperture array, wideband single pixel feeds, phased array feeds, signal and data transport, and science data processor. In the new SKA science book published in 2015, Chinese scholars have made their contributions in 20% of all the chapter proposals. After the SKA1 re-baselining, 20 Chinese astronomers participated in 11 out of the 13 SKA scientific working groups. The “2+1 Strategy” for China’s SKA science priorities has been established, and some important progress has been made in cosmological re-ionization detection as well as in SKA data processing. In June 2015, the Chinese participation in SKA1 passed through the Chinese Academy of Sciences Panel Review. The Chinese Community is now deeply involved into the preparation of the SKA, with activities such as SKA science cases study, researching on high-precision light-weight antennas, developing the Chinese prototype array, as well as some efforts in building an SKA regional data center in China. This article gives a brief historical review of the SKA, overviews some international and domestic progress of the project during its preconstruction phase, and also discusses some future plans of the Chinese SKA.