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Fault current limiters are playing an ever more important role in today's power systems and many of their different types have now reached maturity. Owing to the progress in superconducting technology, the superconducting fault current limiter (SFCL) has attracted increasing attentions. To investigate the efficacy of SFCL devices from a system point of view, the fault current limiting impedance is of great importance. This study proposed an improved structure of flux‐lock type of SFCL and compares the current limiting impedance of different layouts. It focuses on the impacts of iron core shape on primary winding inductance. The analyses include simulations based on finite element method carried out in the simulation software ANAlysis SYStem (ANSYS). This study shows that an E–E‐shaped core with an air gap is better than a closed core when being used for an SFCL. It is also found that for an iron core SFCL with fixed size, its rated fault current limiting impedance can be adjusted by changing the cross‐sectional area of the iron core centre leg and the length of the air gap. [ABSTRACT FROM AUTHOR]

In many countries, it is common for medium voltage (MV) and low voltage (LV) to share the same pole and power line corridor, and this has been a general practice for decades. The MV line and the LV line separation distance may be short under some situations; therefore the mutual coupling may become substantial, which can have a significant impact on network voltages. In the literature, such coupling effect is generally ignored, and there is a lack of a detailed model of the coupled MV and LV lines for incorporation into load flow programs. This study develops a model for unbalanced distribution lines considering the mutual coupling between different voltage levels. Then the established model is utilised in a current injection load flow program to analyse the MV/LV coupling impacts on distribution system voltage. [ABSTRACT FROM AUTHOR]

A hybrid multi‐terminal HVDC (MTDC) scheme combines line commutated converter and voltage source converter technologies for HVDC transmission system. This study presents a comprehensive design of wide‐area power oscillation damper (POD) controller for the hybrid MTDC system. The process consists of input/output selection and parameter tuning for the POD of the hybrid MTDC based on the linearised black‐box model. The objective is to choose an effective control loop to damp the critical mode, which does not have negative impacts on the other modes in the system. For this purpose, a new index, named relative joint interaction index, is proposed for the input/output selection. Afterward, the parameter of POD is tuned using residue‐based phase compensation technique because of its practical application. Finally, non‐linear simulations are also carried out to verify the effectiveness of the designed POD in different loading conditions. [ABSTRACT FROM AUTHOR]

Power system security concerns due to significant wind generation could be twofold: first, the frequency response and second, the short‐circuit performance. Continuous development of wind energy may cause economic replacement and retirement of existing synchronous generators. Modern wind turbine generators do not inherently offer inertia and governor response after a disturbance, which may result in declining frequency response behaviour. Besides, they have limited fault current contribution, which may cause unacceptable short‐circuit ratio at the grid connection point of those wind power plants. Traditionally, frequency response and short‐circuit performance are individually improved. However, both of them are concurrently affected by high wind penetration. Hence, a common approach to simultaneously enhance both indices is essential. Therefore, this study introduces an idea of operating some of the retired synchronous generators in the synchronous condenser mode, which is termed as 'post‐retirement scheme (PRS)'. Such a second use of the retired synchronous generators can jointly upgrade frequency response and short‐circuit strength during high wind generation. This study also proposes a methodology to evaluate when and how much PRS should be deployed for ensuring an adequate security performance in a wind dominated power system. [ABSTRACT FROM AUTHOR]