Smart distribution system is the basic part of smart grid. With the dramatic changes of electric power generation, transmission mode and utilization diversity, the development and operation of distribution systems face not only the pressure in technology application and equipment innovation, but also many new challenges related to integration of distributed generation, electricity market reform and integration of cutting-edge technologies in other areas. The characteristics of smart distribution systems are analyzed in terms of energy flow, information flow and power market, and key technologies are proposed which should be addressed in the near future, including planning of active distribution systems, self-healing control, situational awareness, asset management, information and communication technology (ICT) application, integration of distributed generation, energy storage, etc.The development roadmap of smart distribution systems is illustrated to provide a reference to power system researchers.

An integrated all frequency protection scheme is presented in this paper based on a review of the development of transient based protection and integrated protection. Integrating the conventional power frequency protection algorithms and the transient based protection algorithms, the proposed scheme divides the protection algorithms based on power frequency and transient measurement into three groups: the single end protection group, double or multiple end protection group and backup protection protection group. The single end protection group includes conventional distance protections based on power frequency measurement and boundary and positional protections based on high frequency transient measurement, and these protections are employed to form an instant tripping protection group based on single local end measurement. The double or multiple end protection group consists of conventional current differential protection and time synchronizing transient protection, and these protections are supported by communication link through interconnecting line. The backup protection group includes conventional directional protection and transient protection based on polarity comparison. Finallly, a protection scheme designed for the ultra long length of the half-wavelength transmission line is studied by integrating all frequency domain protection techniques.

The technology and system of regional control and protection based on wide area information exchange are introduced. The information barrier between different secondary systems is broken down, the synchronous operational data is shared between substations, with integrated and optimized function of control and protection for the rigional network. This makes the process of power grid self-healing from fault isolation to supply recovery possible. The key technologies of information exchange, fast backup protection and self-healing control are presented and how to use real-time information to realize, such as high-speed protection, accurate load shedding, generator tripping and optimal auto-switching to the main grid after a regional power network islanded is described. The configuration of the system and communication method are described with a demonstration project. Finally the effect of the engineering application of this technology is demonstrated, which provides a guidance inpractices for future applications.

The new round of electricity market reform in China focuses on reloading the power system deregulation process towards reverting the merchandise property of electricity and setting up its market mechanism. However, it is still in discussion on how to implement the electricity market reform. At present, the electricity market reform in the USA is successful. Its experiences and approaches have reference values for China. This paper introduces the origin of the electricity market in the USA. The role of energy management system in the development of the electricity market and market management system is analyzed. The basic theory of electricity market is discussed as well as the form and implementation methods in the USA, which can provide references for the development and implementation of electricity market reform in China.

Driven by the development of smart grid technologies and information technologies, the future grid operations is evolving from the centralized control supporting load following to the distributed autonomous control supporting the interactions of “source-grid-load”. The cooperative control is the future for the interactive operation of power system to ensure the security of system and support the self-decision of participants. This paper discusses the trend of system operations and control in the future, points out the ubiquitousness of the flexible load and the triple properties of intelligent power unit, proposes a multi-agent based control structure for the interactive operation of grid, discusses the implementation of the multi-level cooperative control and introduces two applications of distributed cooperative control on the interconnected area frequency control and the air conditioner cluster control.

Currently in the domestic distribution network planning field, planners mainly depend on manpower and experience to carry out related analysis, and lack of corresponding quantitative analysis tools support. Based on the planning concept of power supply reliability, an distribution network planning calculation and analysis software is developed applying service-based architecture system, component design, version management mechanism and CIM model exchange technology. The software achieves the core functions, such as power safety analysis, reliability calculation, reactive power optimization and economic evaluation.The software provides data support for current status analysis, planning scheme optimization and planning effectiveness analysis of distribution network. In order to satisfy personalized business requirement of the domestic distribution network planning, this software realizes the quantitative analysis of different distribution network planning schemes by using computer technology and the practical experience of the planners. The software is successfully applied to the distribution network planning of a typical area in one city, which observably enhances the accuracy and effectiveness of the distribution network planning.

An evaluation index system, method and time-spatial extrapolation for smart level of regional grid are presented in this paper. The system employs an index named critical technology adaptability to evaluate the supporting role of key technology to the development of regional grid, and the critical technology adaptability is calculated based on technology readiness level (TRL). Evaluation results are obtained by the combined ordering relation and variation coefficient method. The obtained results are fast predicted in time dimension based on Logistic model, and extrapolated in spatial dimension based on partial least squares analysis for some regions without enough bottom data. The effectiveness of the proposed method and feasibility of the time-spatial exploration are verifid by application instanses of two provincial power grids.

A mathematical model for short-term wind-hydro-thermal load dispatch is built up based on chance-constrained programming considering the stochastic characteristics of load and wind power. In order to make a better balance between local search and global search abilities, an evolutionary predator-prey strategy (EPPS) is used to solve the short-term hydro-thermal generation scheduling and short-term wind-hydro-thermal load dispatch problems. The simulation results show that EPPS can find better solution compared with other algorithms in short-term hydro-thermal generation scheduling. Meanwhile, the approach of chance-constrained programming provides the basis for setting reasonable spinning reserve capacity of system.

Systemetical and full studies on the issue of small-signal angular stability featured by low-frequency power oscillation in power system for over half a century have greatly pushed forward the development of mordern power system. The progress of studies on low-frequency power oscillations of power system are reviewed according to the timeline. Firstly, the discovery of hunting phenomenon of synchronous generators and its solution in earlier time are recalled. Then the theory and experiment researches of low-frequency power oscillations for simple single machine infinite systems are concluded. Secondly, by introducing the theories and methods on damping control and analysis of low-frequency power oscillations, model analysis and damping torque analysis applied to low-frequency power oscillations are reviewed and discussed. Finally, recent research progress on the impact of large-scale wind power integration on power system small-signal angular stability is reviewed.

Many decomposition detection methods of SF₆ decomposition, such as detector tube, gas chromatography, mass spectrometry, and electrochemical method have some shortcomings, for instance, signal overlapp, poor accuracy or reliability, and not being able to realize SF₆ decomposition on-line monitoring. Cavity ring-down spectroscopy (CRDS) technique is proposed to monitor SF₆ decomposition. By studying the SF₆ decomposition mechanism in electrical equipment, the characteristic decomposition products and the corresponding absorption spectrum are analyzed and chosen in terms of CRDS technique. Based on CRDS, an on-line monitoring system of SF₆ decomposition in SF₆ electrical equipment is designed by modular method, and key technologies to improve the accuracy and reliability are explained in details, including cavity matching and anti-jamming technique.

Based on ESAC (energy system analysis consortium) standard of the impedance analysis method, the impedance characteristics and stability for the voltage source converter based HVDC (VSC-HVDC) are analyzed. Firstly, an equivalent circuit of the VSC-HVDC system is established. The impedance characteristics of the VSC-HVDC system are analyzed by using a complex-frequency domain equivalent circuit. A practical stability criterion, based on ESAC standard to determine the stability of VSC-HVDC system, is proposed. Secondly, the Nyquist curves of the VSC-HVDC system under different PI control parameters are calculated and obtained in the complex-frequency domain. The stabilities of the VSC-HVDC system are verified through the Nyquist curves. Finally, the time domain electromagnetic transient simulation results of the VSC-HVDC system performed in PSCAD/EMTDC show that the stabilities of the VSC-HVDC system are similar to that produced in the complex-frequency domain, which further proofs that the presented stability criterion is suitable for stability analysis of the VSC-HVDC system to select the optimal control parameters.

A universal analysis calculation method is presented for DC grid with DC power flow controllers (DCPFC). The impact of DCPFC and the control of converter station are taken into account in the algorithm. Theoretical calculations are carried out to analyze the sensitivity of DCPFC to the power flow controlling. The impact of DCPFC on power flow of DC grid is investigated. The CIGRE B4-58 DC grid test system is modeled in PSCAD/EMTDC to validate the mathematic calculations. Results show that the novel power flow calculation method is accurate.

Traditional PLL algorithms cannot satisfy the requirement of dynamic voltage restorer (DVR) for speed and accuracy during three-phase voltage imbalance sag. Based on analysis of traditional PLL aglorithms, this paper proposed a novel PLL strategy which combines the dαβ-PLL algorithm with a phase prediction method using historial data. During the first cycle of the fault, the phase angle is estimated from the recorded voltage just before the fault occurred; and after the first cycle, the estimated values of dαβ-PLL are then used for phase angle eatimation. The simulation results and prototype test verfied that the proposed PLL strategy is capable to achieve fast phase-locking during three-phase voltage imbalance sag.

With the development of smart grid and renewable energy generation, silicon carbide (SiC) power semiconductor devices start to play an increasingly important role in modern power systems because of its superior physical and electrical properties, such as high power semiconductor density, high voltage, high frequency, and high thermal conductivity. In this paper, the status and development of SiC power semiconductor devices is introduced first, the application prospect of SiC power semiconductor devices in modern power systems is then reviewed and some important application fields such as renewable energy generation, VSC-HVDC power transmission, electrical energy routers and solid state circuit breakers are discussed.

In order to make the modern power system smarter, variable data acquisition devices and information management systems such as smart meters, remote terminal unit(RTU), phasor measurement unit(PMU), and distribution management system(DMS), energy managemt system (EMS), customer management system(CMS), generation management system(GMS) have been widely installed. These systems create huge amounts of data, which are the main sources of smart grid big data. It is imperative for the development of smart grid to study the advanced data analysis technology, which can make optimal decision for power grid control and operation, and also can improve the flexibility, security, reliability, and efficiency of the electricity system. In this paper, the causes of smart grid big data and the importance of data analysis are analyzed, the development trend of big data technology is discussed. Smart grid big data sources and types are selectively analyzed, and then the characteristics of smart grid big data are summarized, the various application scenarios are given, and the smart grid big data analysis platform and function under development are introduced.

IPv6 based advanced metering infrastructure (AMI) is a complete network and system which can process customers’ electric power consumption information comprehensively. It provides an open and standardized communication infrastructure that supports multiple services and business integration. IPv6 based AMI has been implemented by a number of utilties worldwide in recent years. The AMI implementations in several countries and regions together with their solution architecture and operation models are reviewed in this paper. Then the mainstream technology, IPv6 based communication network and AMI infrastructure are introduced. Finally, the benefits and services for power utilities and customers can be enabled by the IPv6 based AMI are analyzed.

In smart grid and energy internet, the security and stability control of power system are impacted seriously by factors such as the reliability of communication network and its latency and bits errors. This paper first gives a review of the current status of the research on hybrid simulation of power system and communication network. After analyzing the characteristics and the dynamic features of SDH (synchronous digital hierarchy) network which supports the power system protection and stability control functions, the framework and key technologies for power system and communication network hybrid simulation platform is proposed, and an interactive hybrid simulation platform for power system and communication network is developed with FASTEST (a power system simulation software) and SSFNET (a communication simulation software) to study the impact of communication failures on the stability control devices. Finally, the impact is verified with the platform on a case of certain provincial power grid.

In order to improve the reliability and the coverage of power line communication (PLC) and satisfy the communication demands of smart distribution grids, this paper proposes a novel cross-band cognitive PLC (CC-PLC) method, where the cross-band incorporates low-frequency band, medium-frequency band and high-frequency band concurrently. The core concept is to enable PLC node to choose its working frequency and communication bandwidth within the cross-band frequencies according to its local channel conditions. By using this paradigm, the communication parameters of PLC can be adjusted on-line, and the disadvantages of traditional narrow-band and broadband PLC, where the working frequencies are preset and can not adapt to the specific and varying channel characteristics, can be well overcome. Moreover, this paper presents some promising key technologies, including channel sensing based on preamble sequence, on-line self-defined physical layer based on equivalent complex base-band (ECB), and self organized network based on multi-frequency flooding. All these solutions have remarkably improved the PLC’s frequency utilization efficiency and its network coverage. A CC-PLC system based on 150 kHz12 MHz is independently developed for field test, which validates the superiority of CC-PLC and reveals its favorable practical prospect in the smart grid.

Traditional calculation modes are not suitable for the modern smart grid, it may restrain the ability to manage sophisticated system or a network with abundant connection of distributed renewable energy, which are most expected in the operation of future power network. In this context, the design of more scalable and more flexible solution paradigms represents a relevant issue to be addressed. Accordingly, a selection from literature published on wind energy generation prediction, data issues and demand response are analyzed and reviewed. The most relevant research trends and the main open problems will be outlined.