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The stability of global economies relies heavily on power systems (PS) that have sufficient operating reserves. When these reserves are insufficient, power systems become vulnerable to issues such as load shedding or complete blackouts. Maintaining grid stability becomes even more challenging with a high penetration of renewable energy sources (RES). However, RES, connected through power electronic devices, offer significant potential as ancillary service (AS) sources. Renewable energy-based microgrids (MG), which aggregate various RES resources and have substantial load control potential, further enhance the capability of AS provision from RES. The presence of diverse AS resources raises the question of how to dispatch ancillary service signals optimally to all resources. Most of the previous research work related to AS allocation relied on single-bus MG models. This paper proposes a detailed MG model for the optimal dispatching of ASs among the resources using Virtual Load, along with an optimization procedure to achieve the best results. The model incorporates voltage profiles and power losses for AS dispatching, and a comparative analysis is conducted to quantify the significance of grid modeling. The model and proposed procedure are tested using the CIGRE microgrid benchmark model. The results indicate that detailed modeling of MG can impact the results by 11%, compared to single-bus modeling, which qualifies detailed MG modeling for all future research work and shows the impact that modeling can have on technical and economic indicators of MG operation. [ABSTRACT FROM AUTHOR]

The stability of global economies relies heavily on power systems (PS) that have sufficient operating reserves. When these reserves are insufficient, power systems become vulnerable to issues such as load shedding or complete blackouts. Maintaining grid stability becomes even more challenging with a high penetration of renewable energy sources (RES). However, RES, connected through power electronic devices, offer significant potential as ancillary service (AS) sources. Renewable energy-based microgrids (MG), which aggregate various RES resources and have substantial load control potential, further enhance the capability of AS provision from RES. The presence of diverse AS resources raises the question of how to dispatch ancillary service signals optimally to all resources. Most of the previous research work related to AS allocation relied on single-bus MG models. This paper proposes a detailed MG model for the optimal dispatching of ASs among the resources using Virtual Load, along with an optimization procedure to achieve the best results. The model incorporates voltage profiles and power losses for AS dispatching, and a comparative analysis is conducted to quantify the significance of grid modeling. The model and proposed procedure are tested using the CIGRE microgrid benchmark model. The results indicate that detailed modeling of MG can impact the results by 11%, compared to single-bus modeling, which qualifies detailed MG modeling for all future research work and shows the impact that modeling can have on technical and economic indicators of MG operation.

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The virtual load method is studied in this paper for damage assessment of beam type structures. The main advantage of this technique is that damage assessment can be accomplished by using only the vibration modes of the current structure. A series of virtual load vectors are constructed to obtain the same pure bending states for different segments of the beam. And then the curvatures of these segments loaded in pure bending are compared to identify the damage locations and extents. It was found that the proposed method is very suitable for damage assessment of those existing beam type structures.

• A new concept of quasi-frequency response function (Q-FRF) is proposed. • A new method of dynamic load localization using Q-FRF is proposed. • Simulations and experiments for the proposed method have been carried out. • The effectiveness of using different types of response to locate load is verified. • The noise resistance and robustness of the method are verified. In this paper, a novel concept of quasi-frequency response function (Q-FRF) is proposed and applied to dynamic load localization. Aiming to avoid the ill-posed problem in FRF matrix inversion and improve the identification accuracy and calculation efficiency, a new method for fast load localization is developed based on the proposed Q-FRF. In the application of this new method no FRF matrix inversion is required. By utilizing the measured vibration response and the origin real FRF, the virtual loads at possible load application locations can be obtained. Then, the cross point Q-FRF for each measurement point are obtained using the virtual loads and measured response. Finally, the correlation coefficient between the cross point real FRF and the cross point Q-FRF is used to indicate the dynamic load location. The feasibility and effectiveness of the proposed method are validated by case studies on typical engineering structures: a fixed-support beam and a cantilever support stiffened panel. The objects are subjected to random loads and impact loads beforehand. Both types of loads can be well located by the proposed method using Q-FRF. Furthermore, noise resistance and robustness of proposed method were also tested in the present study. [ABSTRACT FROM AUTHOR]

This paper proposes a two-stage decentralized optimal reactive power dispatch (D-ORPD) framework, which considers the network partitioning influence in distributed optimization. The first stage is to divide the distribution networks (DNs) into several high-intra-cohesion and low-coupling sub-networks while the mathematical model is constructed based on partition indexes. This optimal partition designation reduces information exchange between adjacent sub-networks. Then, with the reduced information exchange, the distributed computation would be accelerated. Based on the network optimal partition, the D-ORPD model is constructed in a “decomposition-coordination”pattern during the second stage. To enhance the consistency between distributed and centralized optimization, the D-ORPD is improved by the proposed virtual load, which simulates the load characteristic of sub-networks. The alternating directions method of the multipliers (ADMM) algorithm is utilized to solve the mathematical model effectively. Moreover, case studies on the PG&E 69 bus test system and the IEEE 123 bus test system are executed by the MATLAB platform to demonstrate the validity and effectiveness of the proposed method.

The PLC curriculum is highly practical. In order to achieve a good teaching effect, it must be equipped with experimental devices for a large number of practical training. The control objects of the PLC are various and it is not only unrealistic but also costly to develop a physical experiment device for each control object. Although the use of computer simulation software for virtual simulation experiments can solve the PLC experiment teaching the difficulties of physical experiments, but it does not involve hardware wiring debugging, and cannot train students’ engineering ability. Aiming at the above situation, a virtual load experiment device based on SCM is designed. With the help of the rich resources of configuration software, the realistic control model can be constructed. At the same time, the hardware interface circuit designed by the SCM is used to implement the hardware connection training. Practice has shown that this experimental device with a combination of hardware and software has significant effect on the practical teaching of PLC. [ABSTRACT FROM AUTHOR]

This paper develops an analytical method for assessing the safety margins of a generation rejection scheme (GRS) reliably. It also presents a practical framework for implementing the proposed method integrated with energy management system and synchrophasor data in power grid operations. By employing a concept of virtual load connected to the critical generation bus of the single machine equivalent of the real-time operations case, we calculate, similar to transfer analysis, the allowable power to the virtual load in MW after tripping the pre-planned number of generation units and thus determine the required rejected power for the GRS initiating scenario. This virtual loading can be interpreted as the safety margin of the designed GRS to ensure its stabilizing operation. This research further develops a computationally efficient technique for refining the safety margin potentially with the measured synchrophasor data to improve the robustness of the GRS in practice. Understanding the safety margin is envisioned to help investigate and identify other practical options than tripping generators for protecting the system integrity. Accuracy and efficacy are demonstrated for real Korea power system cases. [ABSTRACT FROM PUBLISHER]