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For UHVDC converter stations, when the AC or DC system fault occurs, it will cause a fluctuation of AC bus voltage, and the lack of local dynamic reactive power compensation will greatly increase the risk of power system voltage instability, so a new generation synchronous condenser is introduced at the converter station. To examine the effectiveness of the synchronous condenser and its control system, the real-time digital simulator (RTDS) is used to establish the closed-loop real-time digital simulation system of the ±800kV UHVDC transmission system. The simulation results show that the AC bus voltage fluctuation caused by switching AC filter or capacitor, the various DC system faults and AC bus faults can be restrained, and the synchronous condenser is able to change the nature and size of reactive power flexibly, and to provide transient reactive power support for DC system, so as to improve the voltage stability of the AC/DC hybrid network.

A precision positioning system with energy efficiency is of great necessity for guaranteeing personnel safety in underground mines. The location information of the miners’ should be transmitted to the control center timely and reliably, therefore, a heterogeneous network with the backbone based on high speed Industrial Ethernet is deployed. Since the mobile wireless nodes are working in an irregular tunnel, a specific wireless propagation model cannot fit all situations. In this paper, an underground localization system is designed to enable the adaptation to kinds of harsh tunnel environments, but also to reduce the energy consumption and thus prolong the lifetime of the network. Three key techniques are developed and implemented to improve the system performance, including a step counting algorithm with accelerometers, a power control algorithm and an adaptive packets scheduling scheme. The simulation study and experimental results show the effectiveness of the proposed algorithms and the implementation.