Daiming Yang

Pollution flashover of transmission line insulator seriously affects the safe operation of the power system. The insulator contamination is mostly deposited in dry weather, while the existing leakage-current-based pollution warning models could only send out a warning signal at a saturated moisture level, which seldomly happens and would be late for the pollution warning for online insulators. To monitor the change of insulation pollution degree under unsaturated humidity, a new method based on the humidity change and insulator contamination wetting characteristics is proposed in this article. It has been found that under 75%–99% relative humidity (RH), with the change of atmospheric humidity, the water content of the contamination changes from an equilibrium value to another equilibrium value exponentially, resulting in a linear relationship between the leakage current and the relative humidity with a slope proportional to the insulator pollution degree. Therefore, the site pollution degree of insulators can be obtained by the minute measured value.

Nowadays, end fitting corrosion reduces the mechanical strength and flashover voltage of insulators, forming a huge threat to high‐voltage direct current transmission lines. At present, the parameters of electrolytic corrosion inhibition measures are selected based on the premise of the constant annual corrosion rate. However, with the development of corrosion, corrosion products accumulate on the insulator surface, which may impact the corrosion rate. In order to clarify the influence of corrosion products, this work studied how corrosion products influence the corrosion rate from the corrosion phenomenon, corrosion current, feature and formation of corrosion products. The results showed that corrosion products of iron and zinc were excellent in adhesion on the insulator surface and could not be cleaned by rain, which was able to increase the corrosion rate. In future, in the selection of the quality of the zinc ring bonded on insulator fittings, there will be a demand to consider the influence of corrosion products on the corrosion rate.

Misalignment of wireless power transfer (WPT) system’s transmitting and receiving ends can cause severe efficiency degradation and electromagnetic radiation. In this paper, a novel parallel transmission (TX) coil matrix structure was proposed to improve the performance of the WPT in the misalignment condition. The receiving (RX) coil’s position measurement method was innovated by investigating the magnetic field and the mutual inductance change caused by the relative position change between RX and TX coils. Both theory and experiments confirmed that the phase difference between signal coil and detector coil can be featured as the parameter to represent the magnetic field’s change. Based on this principle, a 4×4 TX coil matrix was made which verified the proposal and the sensitivity of the sensor. It was found that the position measurement result was sufficient to decide which TX coil to gate to facilitate the wireless charging in misalignment conditions. The structure and the size of the TX coil matrix could be further optimized to enhance the sensor’s reliability and sensitivity.

The evaluation of the electrolytic corrosion on the hardware of insulators is necessary for long-term operation and maintenance of high-voltage direct current (HVDC) overhead lines. In this paper, the design and development of an online monitoring system are introduced for the measurement of corrosion current and the charge in porcelain and glass disc suspension insulators. A wide range current sensor of a mu A-mA level was developed to sample the surface corrosion current. The data acquisition module connected to microampere current sensors, ambient temperature, and relative humidity sensors transmitted filed information to a remote Internet server via general packet radio service. Laboratory tests were carried out to verify the system performance, including the accuracy of current measurement, the stability of power supply, the reliability of communication, and electromagnetic compatibility. It was found that there was good agreement between the monitoring results and the dissection results. Six devices were installed on transmission towers of three +/- 800-kV HVDC projects in different regions, and all of them have been operating for more than two years from 2015 to 2017. Data stored in the server were exported for further analysis in this paper. Summary statistics on different time scales showed the relationship between corrosion and regions. Based on the records of the most seriously corroded caps, relative humidity and rainfall were found to be two major factors affecting the corrosion rate.

Tracking the state-of-charge (SOC) is important for battery applications. A novel SOC estimation algorithm based on extreme learning machine (ELM) is proposed. Compared with the traditional neural network method, the ELM simplifies the computation procedure and shortens the learning time. A typical model of ELM is built for an 180Ah/3.2V lithium iron phosphate battery, and data acquired from cell discharge experiments under a series of current are contributed to model training and predicting. To evaluate the effect of ELM on SOC estimation, the back propagation (BP) neural network and the support vector machine (SVM) are taken into comparison. The results show that the ELM method provides a more accurate SOC. What is more important is that the speed of network training is improved greatly.

Lithium-ion battery packs based battery energy storage system (BESS) has proved its high potential in energy storage. In studying the BESS, A precise battery model is critical for implementing the system simulation, estimating the SOC, SOH of the battery, as well as optimizing the design. An electric model which can reflect the hysteresis effect and dynamic characteristic is adopted in this paper, and based on that, we proposed a novel method for battery model identification and on-line correction of model parameters by extended Kalman filter (EKF). Thus the parameters of battery model can be regulated in the progress of battery charge and discharge. The method is proved to be efficient and accurate by comparing the simulation result with the experiment data