A Novel Method of Static Security Analysis Based on Multithread Technology

This study presents the analysis of debates on the future super grid in China. The rapid increase of power demands and the uneven distribution of energy bases and load demands in China require bulk‐capacity long‐distance power transmission. Two candidate solutions are thus proposed, that is, the ultra‐high‐voltage ac (UHVAC) synchronous power grid and the extra high‐voltage ac (EHVAC) asynchronous super power grid. The debates on the above two power grids are first reviewed. The two candidate power grids are then compared in detail in terms of security, economic and environmental aspects. Finally, this study provides a suggestion for the construction of UHV synchronous power grid in China as well as the future research direction. The research, discussion and conclusion related to UHVAC and EHVAC transmissions in China are expected to provide useful references for power system planning in other countries and to promote the development of the global power industry.

Role of optimal transmission switching in accommodating renewable energy in deep peak regulation-enabled power systems

Based on an analysis of the misunderstanding and problems concerning wind power development, this paper summarizes the experiences of coordinated development of wind power and power grids in typical countries, proposes the principles and strategies for the coordinated development of wind power and power grids in China. Technically, bidirectional friendly technologies should be deployed to ensure the security of power system. In regulatory term, a complete and standardized regulatory strategy is key to harmonious interaction among different stakeholders concerning wind development. Incentive policies should be comprehensive, foreseeable and sustainable. Related measures and suggestions for large scale development of wind power in China are put forward.

A novel capacity demand analysis method of energy storage system for peak shaving based on data-driven

Studying the propagation of cascading failures through the transmission network is key to asses and mitigate the risk faced the energy system. As complex systems the power grid failure is often studied using some probability distributions. We apply 4 well-known probabilistic models, Poisson model, Power Law model, Generalized Poisson Branching process model and Borel-Tanner Branching process model, to a 14-year utility historical outage data from a regional power grid in China, computing probabilities of cascading line outages. For this data, the empirical distribution of the total number of line outages is well approximated by the initial line outages propagating according to a Borel-Tanner branching process. Also for this data, Power law model overestimates, while Generalized Possion branching process and Possion model underestimate, the probability of larger outages. Especially, the probability distribution generated by the Poisson model deviates heavily from the observed data, underestimating the probability of large events (total no. of outages over 5) by roughly a factor of 10-2 to 10-5. The observation is confirmed by a statistical test of model fitness. The results of this work indicate that further testing of Borel-Tanner branching process models of cascading failure is appropriate, and should be further discussed as it outperforms other more traditional models.

Wind damage is one of the common disaster that has serious influence on China’s power grid. The wind damage has a wide distribution and a low success rate of reclose, which makes the transmission line outage more likely. In this study, it is found that the 2016 wind damage of power grid in China’s major areas mainly distributed in the southeastern coast, southwest region, north China and its surrounding areas. In temporal distributions, wind damage mainly occurs in summer and afternoon. In 2016, the first reclose success rate of wind damage trip is only about 10% during 330 kV and above voltage level transmission lines. 220 kV is a voltage level threshold of trip line: tripps number increases with voltage level decreases when above the threshold, otherwise trips number decreases with voltage level decreases. Transmission line wind damage trip trend has a large interannual variation from 2010 to 2016. This study analyzes the characteristics of wind damage trips in 2016, which provides guidance for wind damage prevention work in windbreak-prone areas and windbreak-prone periods.

East China Grid is a branch of the State Grid Corporation of China that operates the largest regional power grid in China which provides electricity to four provinces and Shanghai, about 258 million people. As the national leader in the development of offshore wind farms and nuclear power plants, East China Grid is also the primary receiving end of national ultra-high voltage backbone power grids. However, intermittent outputs by renewable sources and inflexible ultra-high voltage direct current together threaten the viability of maintaining reliable and high-quality electric service for consumers. This paper proposed practical ways for East China Grid Corporation to absorb renewables as much as possible under its high proportion of coal-fired power plants. It shows that pumped hydropower plants still have potential to help more about peak-regulation but require market incentives. And the nuclear power plants in East China Grid which equal half of nationwide nuclear capacity, will contribute significantly via load-following operation.

With the rapid development of the Chinese power grid, its dynamic behavior becomes increasingly complex. How to prevent voltage instability and voltage collapse at the receiving-end system has become an urgent problem at present. To prevent voltage collapse, the key is to determine the stability margin at the operating point of the power system, and the load margin is the most basic and widely accepted voltage stability margin indicator. Considering the role of medium and long-term slow-acting elements in the actual system that affect the system voltage stability, this paper combines the static voltage stability analysis with the transient, medium, and long-term dynamic voltage stability analysis based on whole process simulation, and uses time-domain simulation methods to evaluate the voltage stability of the actual system. By analyzing the various dynamic characteristics of generator overexcitation limits and transformer on-load regulation on the development process of voltage-collapsing accidents, this paper proposes an evaluation index for the whole process dynamic stability margin of the receiving-end system. On this basis, the whole process dynamic defense system of the power grid is also constructed. The proposed method is validated by using a provincial power grid in China as an example.

In power system operation, there are usually a few vulnerable lines (VLs) which are prone to exacerbate the propagation of cascading failures and lead to severe blackouts with high probability. To facilitate preventing the power grid from cascading blackouts, in this paper, a PageRank-based fast screening method is derived to identify VLs. To this end, we extend the concept of interaction graph to model cascading outages as a directed weighted graph, where impacts of hidden failures are first taken into account. Based on the graph, we modify the celebrated PageRank algorithm to derive an ultra-fast VLs screening algorithm for large-scale power grids. Simulations carried out on the IEEE 118-bus system show that the proposed method can achieve high-accuracy VLs screening while the speed can be enhanced for several orders of magnitude compared with cascading failure simulation methods. Tests on a 1122-bus real power grid in China demonstrate that it can discriminate the most VLs in a practical power grid within only several minutes, showing its great potential for on-line application.

Performance and reliability of electrical power grids under cascading failures

Chinese energy resources and load are in reverse distribution, and it is necessary to vigorously develop UHV AC and DC technologies suitable for long-distance and large-power transmission. The pattern of UHV AC-DC hybrid power grid has been initially formed at present. However, the faults of UHV DC with large transmission power and complex fault forms have great impact on the power grid in both active and reactive power. In this paper, based on the analysis of the current situation and characteristics of UHV AC/DC power grids in China, the impact of UHV DC restart and commutation failure on the stability of the power grid is analyzed. The different types and triggering factors of DC commutation failures are analyzed, and the effects of single or multiple DC commutation failure types on the transient angle stability, the voltage stability and the transient overvoltage are simulated. The UHV DC restart fault time sequence is studied, and the effects of different restart modes on the system transient angle stability and transient overvoltage are demonstrated through simulation. The research results have laid the foundation for grasping the UHV DC fault morphology mechanism and the influence law on the stability of the power grid, and provided support for the safe and stable verification of the UHV AC/DC power grid.

Novel complex network model and its application in identifying critical components of power grid

The state grid corporation of china has been deploying ultrahigh-voltage (UHV) ac technology on a large scale since launching its Strong and Smart Grid plan in 2009. China has 80% of its hydropower generation in the southwest and 76% of its coal generation in the northwest. However, more than 75% of the country's energy demand is distributed in the eastern and southern coastal areas. This geographical mismatch between supply and demand made it necessary to build UHV transmission networks: transmission technologies at voltage levels of 1,000 kV for ac and p1,000 kV for dc. In this article, the development of UHV transmission-system technologies and projects is detailed, with a focus on the UHV ac transmission system.

The inter-transmission of sub-synchronous electrical parameters between AC and DC sides of HVDC power transmission system is analyzed by switching functions of converter, and in term of sub-synchronous frequency the mechanism of sub-synchronous oscillations (SSO) in power grid caused by the control system of HVDC system is expounded. By use of complex torque coefficients in time-domain simulation the sub-synchronous damping characteristic of AC/DC power grid is researched in detail, and the principle of suppression SSO by supplementary sub-synchronous damping controller (SSDC) is emphatically discussed, then the design approach for the design of modal control-based SSDC is proposed. In allusion to an actual SSO occurred in a certain power grid in China, a modal control-based SSDC is designed. The correctness of the principle applied in the design of modal control-based SSDC and its effectiveness in suppressing SSO are verified by time-domain simulation.

In order to effectively improve the operating environment of large-scale power grid and effectively monitor the safety of power grid, this paper analyzes the concept of smart regulation system for large-scale power grid based on big data and artificial intelligence (AI) in the new era environment of smart operation, then analyzes problems existing in the current dispatching system of large-scale power grid in China, as well as the specific needs of smart dispatch system in the design process. And the corresponding smart control system is designed to effectively optimize and improve the operation environment of power grid, and upgrade and improve the core technology of smart dispatching system of power grid.