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The increasing permeation of the distributed generators in the power system brings great challenges for fault diagnosis, especially for the distribution networks with ungrounded neutral or grounded by Peterson coil as the fault current is limited and easily affected by the noises and interferences. A single phase-to-ground fault section identification method is proposed based on feature extraction of the synchronous waveforms and the calculation of the eigenvalues for the time-sequenced features. First, several fault features are defined and extracted from the synchronous current waveforms obtained by the fault recorders. Then, the topology related fault feature matrix is constructed using the time-series features obtained from different measurement sites, and the eigenvalues of the matrix are calculated based on the random matrix theory. Lastly, using the distribution characteristics of the eigenvalues, improved K-means clustering algorithm is utilised in classifying the fault cases and identifying the faulty sections. The effectiveness of the proposed scheme is verified by IEEE 34 nodes test system and a multi-feeder distribution network. [ABSTRACT FROM AUTHOR]

Due to the increasing penetration of variable renewable energies, the primary frequency response (PFR) capability of thermal power units is becoming more and more significant for power systems to tackle abrupt active power disturbances. Moreover, the actual thermal states of boilers that are usually assumed to keep rated and constant may degrade PFR capability, and incur unexpected severer frequency deviations and even instability. This study proposes an extended system frequency response (ESFR) model incorporating the influence of thermal states on PFR. The ESFR model is developed by extending the system frequency response (SFR) model with a boiler thermodynamic sub‐model, of which a low‐order and linear time‐domain expression is derived. Then, a quantitative assessment framework is established to assess the influence of thermal states on PFR capability, in which the instantaneous and accumulative quantities are calculated via the expressions of the ESFR and SFR models. Furthermore, based on the developed ESFR model, an improved estimation approach of dynamic frequency response considering thermal states is provided for the preliminary application. Case studies are conducted to validate the proposed model and approach. [ABSTRACT FROM AUTHOR]

With ultra high voltage direct current (UHVDC) and flexible alternating current transmission systems (FACTS) have been widely applied in power system, the AC/DC power grid is constantly extending which makes its composition more complicated. The independent electromechanical transient simulation and electromagnetic transient simulation cannot meet the need of rapidly developing modern power system in simulation technology. Electromechanical–electromagnetic hybrid simulation not only has the advantages of analysing large systems, but also accurate description of power electronic components. Analysing errors in hybrid simulations can help them to quantitatively analyse different hybrid simulation interface technologies to optimise simulation settings. Concerned fault types, fault location, and point fault cleaning time, an electromechanical–electromagnetic hybrid simulation scenarios probabilistic model based on Monte Carlo is put forward. Then adopt Prony method to quantitatively analyse the hybrid simulation errors. Through a typical example of UHVDC power grid in Shandong province, the error evaluation method of the hybrid simulation is demonstrated in detail. The research shows that this kind of assessment method can well analyse the numerical validity of hybrid simulation. [ABSTRACT FROM AUTHOR]

Micro-transmission lines are the physical model elements that own the same physical properties as the real transmission lines in power system, which are the significant components of a micro-dynamic simulation laboratory. This study presents an integrated experiment cabinet for micro-transmission lines (IECMTL). IECMTL integrates 20 micro-emulating transmission lines units, four micro-bus units and two light-synchronised phasor measurement units (PMU Lights). Benefitting from the same size and interface, researchers can change the position and wiring of any two transmission lines units according to the needs of the simulation experiment. PMU Lights are employed to get the operating status of micro-emulating transmission lines, including three-phase frequency, voltage phasor and current phasor. Appropriate software was developed on server to communicate with IECMTL in a two-way manner through the internet. Real-time monitoring and control features of IECMTL provide a flexible physical platform not only for innovative research ideas but also for education engineering of the power system. An example test-bed consisting of two IECMTLs was presented to simulate the power grids containing three generators and nine buses. [ABSTRACT FROM AUTHOR]

Power flow calculation is a basic tool for power systems operation and control. Considering static frequency regulation characteristics of power systems, dynamic power flow (DPF) gives more precise results of system operation with frequency deviation than conventional power flow. The increasing penetration of wind energy into power grid makes it necessary to take wind power into consideration in DPF calculation. The operational traits and frequency regulation characteristics of major types of wind turbines are discussed, including fixed speed wind turbines and variable speed wind turbines with integrated control strategy combining over‐speed control and droop control. With the primary frequency regulation characteristics of wind turbines, a simplified DPF algorithm is proposed in this study for power systems integrating wind power generation. The IEEE 30‐bus system is modified to verify the proposed method considering different levels of wind power penetration. [ABSTRACT FROM AUTHOR]