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Criteria and indices of transient voltage stability have attracted much attention recent years. It is a difficult problem since dynamics of load components are involved, such as induction motors and HVDC converters. A transient voltage stability index based on critical equivalent impedance and time-domain simulation is proposed in this paper. Firstly, two different static voltage stability indices based on Thevenin equivalence are introduced, and the second one provides a new idea to transient voltage stability analysis. Secondly, a transient voltage stability index is proposed, and an equivalent system is built up after a large disturbance, with a time-variant Thevenin equivalent circuit and a dynamic load. Thirdly, the algorithm process and flowchart are put forward. Fourthly, online applications of the proposed index are discussed. Finally, the proposed index and algorithm are tested on two test systems and a practical power system. Simulation results demonstrate its effectiveness and feasibility.

Due to severe geographical conditions, limited investment and environmental pressure, HVDC sending systems are often weakly interconnected with main network, Sometimes HVDC sending systems may even operate in islanded mode. Over-voltage/low-voltage after large disturbances becomes a serious problem. Static over-voltage/low-voltage problem in weakly interconnected or islanded HVDC sending systems is studied in this paper. An optimization method for dynamic reactive power reserve based on quasi-steady state sensitivity is proposed. Firstly, sensitivities of generator reactive power and bus voltage to reactive power disturbance are derived. Secondly, a method to calculate voltage variations with a sensitivity method considering HVDC transmission systems is put forward. Thirdly, system effective dynamic reactive power reserve is defined and deduced. Fourthly, an optimization model and process for dynamic reactive power reserve is come up with. Finally, the proposed algorithm is tested on a practical power grid. Simulation results demonstrate its effectiveness and feasibility.

In order to get the excellent accuracy for price forecast in the cell phone market, a novel improved Sliding Window (SW) model based on adaptive windows width and a novel improved Radial Basis Function (RBF) Neural Network (NN) model based on adaptive spread are proposed and the Disturbance Factors Model (DFM) is used in this paper. All of the three kinds of price forecasting models are utilized to verify the accuracy. The cell phone price is extracted from different websites and used as the model verification data. And the experimental results of the forecasting average accuracy based on the DFM obtain 94.61 percent. The experimental results of the forecasting average accuracy based on the ARBF NN model obtain 97.88 percent. The experimental results of the forecasting average accuracy based on the Adaptive SW Model (ASWM) obtain 99.64 percent. Although the results based on the DFM are not very good, it is still a satisfactory result. Since it is at least not a very serious result which proves that it is worth to do further researches in the field of the cell phone market based on the DFM. The results based on the ASWM and the ARBF NN models are satisfied. The improved methods enhance the forecast accuracy compared to the original model. In the field of the price forecast on the cell phone market, the improved methods have a good performance which is valuable and useful not only for businesses, but also for consumers.

The nature of voltage collapse is that as power transfers into a well-bounded region are increased, the voltage profile of that region will become lower and lower until a point of collapse is reached. Continuation power flow (CPF) is a powerful analytical methodology and tool in static voltage stability analysis. Engineer may use P-V method for general voltage stability evaluation, contingency screening, etc. The benefits of this methodology is that it provides an indication of proximity to voltage collapse throughout a range of load levels or interface path flows for the simulated system topology. The reactive power resources are needed to supply the requirements of customer demands and the reactive power losses in the transmission and distribution systems, and provide adequate system voltage support and control. Therefore, the modeling of generator reactive power limit is very important in CPF. The reactive power characteristic under generator excitation current limit were discussed; Based on the former generator reactive power limit treatment, a new method of reactive power dispatch under the excitation current limit adapted in CPF calculation was given out; Simulation used the improved algorithm were done. The simulation results of the IEEE 30 system show that the proposed model is effective and rational.

This paper deals with the history of development, present status and future perspective of electric power system in China. The development of nationwide interconnected grid, purpose of interconnection, key projects and R&D necessary for future are discussed. The nationwide interconnected grid will be basically established in 2020 and become one of largest power systems in the world.

Some utilities in Australia are also looking to the high growth electricity markets of the Asia-Pacific region to further their business growth. Some are achieving credible successes in this region. In order to realize the full potential of competition in the electricity market, it is necessary that there be complementary reforms in the gas industry. Gas competes with electricity in meeting customer’s thermal energy needs. Advances in gas turbine technology are now such that gas is becoming competitive with Australia’s low-cost coal resources for electricity generation. In addition, increasing global concerns over the greenhouse emissions favor gas as an alternative source of energy. A competitive market in gas will encourage investment in development of gas resources and technology and gas plant contributing to an efficient energy industry. The forces of competition, technology development, and of the environmental imperatives are combining to dramatically affect how energy is supplied and used. These forces will have strong policy implications for the energy industry in the pursuit of increasing Australia’s international competitiveness and prosperity. Competition reforms, efficiency improvements, and investment in technology development have positioned the Australian electricity industry to meet the challenges of markets looking increasingly for sustainable energy solutions.