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To address the optimal inertia allocation after replacing the moment of inertia with virtual inertia in power systems， a method for virtual inertia allocation based on grey wolf optimization （GWO） is proposed. Firstly， the demand for inertia in high-proportion renewable energy power systems is determined. Secondly， considerations include factors such as frequency stability and investment cost of virtual inertia. An optimal model for virtual inertia allocation is constructed with critical inertia， rate of change of frequency （RoCoF）， and maximum frequency deviation as constraints， as well as with the objective of minimizing the frequency safety index and investment cost. The GWO is employed to solve the model. Finally， simulation analysis is conducted using the modified WSCC 9-bus system and IEEE 39-bus system as examples. The results validate the effectiveness and universality of the proposed method.

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While aiming to increase the dispatch of variable energy resources (VER) during the operation of a power system, the stability of the power system should be maintained, which can be realized by evaluating the penetration limit of the VER. This paper proposes a method for evaluating the penetration limit of VER. When a disturbance such as a generator trip occurs, the frequency stability depends on the inertia energy secured by generators, the characteristics of the primary frequency response, and the load response, which would change owing to an increase in the VER of the power system. In the proposed evaluation method, the frequency response performance of the power system is analyzed based on the historical operation data, and the penetration limit of VER is evaluated by applying the frequency criterion to maintain the frequency stability of the power system. Therefore, the potential penetration limit of VER can be estimated depending on the operating conditions. In addition, the effectiveness of the proposed evaluation method is verified by comparing the simulation results based on the Korean power system model-based simulation, and the online application is evaluated by applying it based on the real system operation data.

Critical inertia can be defined as the minimum kinetic energy stored in generators that should be kept for maintaining the frequency stability of the power system. As the frequency control performance of the power system is maintained according to its control criterion, during the inertia response time frame, the expected energy imbalance can be calculated by accumulating the imbalanced power caused by the credible contingency and calculating the available inertia response by considering the allowable operating limit of the frequency. Since the frequency control criterion can be met when the available inertia response becomes larger than the expected energy imbalance, the critical inertia can be calculated by the kinetic energy of the generators, of which the available inertia response is equal to the expected energy imbalance due to the contingency. With this in mind, this paper derives the energy balance condition for the frequency stability in the inertia response time frame based on the frequency control criterion and calculates the minimum inertia, which should be kept in the generators from the energy balance condition for meeting the criterion. In addition, the effectiveness of the proposed method is verified through various case studies employing Korean power systems. [ABSTRACT FROM AUTHOR]

Critical inertia can be defined as the minimum kinetic energy stored in generators that should be kept for maintaining the frequency stability of the power system. As the frequency control performance of the power system is maintained according to its control criterion, during the inertia response time frame, the expected energy imbalance can be calculated by accumulating the imbalanced power caused by the credible contingency and calculating the available inertia response by considering the allowable operating limit of the frequency. Since the frequency control criterion can be met when the available inertia response becomes larger than the expected energy imbalance, the critical inertia can be calculated by the kinetic energy of the generators, of which the available inertia response is equal to the expected energy imbalance due to the contingency. With this in mind, this paper derives the energy balance condition for the frequency stability in the inertia response time frame based on the frequency control criterion and calculates the minimum inertia, which should be kept in the generators from the energy balance condition for meeting the criterion. In addition, the effectiveness of the proposed method is verified through various case studies employing Korean power systems.

The paper presents the Line Start Synchronous Reluctance Motor (LSSynRM) technology as a promising avenue to bring IE3 motor portfolios to the IE4 efficiency class at contained manufacturing costs. Indeed, the achieving of IE4 efficiency class is concerning many motor manufacturers, where the small-medium manufacturers seem to face the higher efforts in converting their product portfolio. To this extent, a methodology to improve the IE3 Induction Motor (IM) efficiency by introducing the Line Start Synchronous Reluctance motor technology in the IM motor is presented. The new motor design guidelines and constraints are figured out to reduce the impact on the manufacturing process. The paper presents a detailed experimental validation of the realized prototype in steady-state and transient operation referring to a target IE3 IM. The prototype proved to be a cost-effective, mass production-ready solution for super-premium efficiency IE4 motors. The LSSynRM technology demonstrated to be an effective high-efficiency avenue at reduced manufacturing costs in a broad panorama of low-inertia industrial applications.

Since line-start synchronous permanent magnet motors (LSPMs) entered the market, they have attracted research interest toward counterpart induction motors of low power-ratings. This paper reports an investigation of line-start synchronous reluctance motors (LS-SynRMs). LS-SynRMs has not been investigated as much as LSPMs have. A motor needs to maximize rotor saliency to achieve high efficiency and a high power-factor. This results in complicated rotor geometry because the rotor cage and multiple flux barriers share the same rotor space. This paper provides an approximate method based on steady state torque analysis by which to estimate the critical inertia of a LS-SynRM. A finite element analysis (FEA)-aided analytical approach to the approximation of steady state torque is proposed to replace the more typical approach based on equivalent circuit parameters. The critical inertia resulting from the proposed method is compared to the results obtained using the FEA. [ABSTRACT FROM AUTHOR]

Since line-start synchronous permanent magnet motors (LSPMs) entered the market, they have attracted research interest toward counterpart induction motors of low power-ratings. This paper reports an investigation of line-start synchronous reluctance motors (LS-SynRMs). LS-SynRMs has not been investigated as much as LSPMs have. A motor needs to maximize rotor saliency to achieve high efficiency and a high power-factor. This results in complicated rotor geometry because the rotor cage and multiple flux barriers share the same rotor space. This paper provides an approximate method based on steady state torque analysis by which to estimate the critical inertia of a LS-SynRM. A finite element analysis (FEA)-aided analytical approach to the approximation of steady state torque is proposed to replace the more typical approach based on equivalent circuit parameters. The critical inertia resulting from the proposed method is compared to the results obtained using the FEA.