Stochastic Approach to Hosting Limit of Transmission System and Improving Method Utilizing HVDC

According to the global de-carbonization trends, renewable energy integration has become an increasingly important issue in power systems. To achieve 100% renewable energy integration and operate a system with these resources, it is necessary to appropriately evaluate the system hosting capability and prepare appropriate planning and operation strategies using the evaluation result. So far, these interests have focused particularly on distribution-level systems. However, although the hosting limit in transmission-level systems requires further consideration, previous study is limited. This study introduces the constraints on the transmission-level hosting limit. In addition, a stochastic estimation of the hosting limit methodology in the transmission system and the use of a high voltage direct current system to improve hosting capacity are proposed and evaluated. Moreover, these methodology-based simulations are conducted using possible scenarios on the IEEE 39 bus system with some constraints, and the simulation results are presented herein. The results showed that the HVDC location selection and operation using the proposed method and optimization technique is appropriate. The strategy can be used to integrate more renewable energy. Furthermore, the proposed methodology can be applied to renewable energy integration scenario establishing a plan.

An RTDS-Based Testbed for Investigating the Impacts of Transmission-Level Disturbances on Solar PV Operation

The increasing penetration of renewable energy resources such as solar and wind via power electronic inverters is challenging grid dynamics, as well as grid planning, operation, and protection. Recently, the North American Electric Reliability Corporation (NERC) has reported a series of similar events of the unintended loss of solar generation in Southern California over a large geographic area following the transmission-level disturbances. These events highlight the importance of understanding the characteristics of the transmission-side disturbances propagating into the distribution systems and their impacts on the operation of inverter-based resources. In this paper, a real-time electromagnetic simulation testbed is constructed for real-time electromagnetic simulations to generate realistic transmission-level disturbances and investigate their impacts on the solar PV operation under different fault types and locations, solar penetration levels, and loading levels. Through the simulation analysis and grid strength assessment, it is found that the grid strength at points of integration (POIs) of solar PVs significantly affects the transient stability of solar generators. Particularly, undesirable transient stability events are more likely to occur at the weak POIs following the transmission-level disturbances. Moreover, undesirable transient stability events become severer when the transmission-level disturbance is closer to the weak POIs or the disturbances become more serious. Additionally, the impact of the transmission-level disturbances on the solar PVs at the weak POIs exacerbate with the increasing solar penetration levels and loading levels. Thus, it is important to study and develop new technologies for grid planning, operation, and protection in weak grid conditions to address the emerging issues of integrating the high penetration of solar PVs and other IBRs.

Modeling and simulation of power system protection relays in a transmission-level application

This report presents the findings of an in-depth literature review on protective relaying. The project focuses on protection system practices which are relevant to transmission-level applications. Various implementations of differential, phase distance and ground distance relays were investigated and ultimately modeled in the Matlab Simulink environment. A further model for a saturable iron-core current transformer was also investigated and developed. These models were tested to ensure compliance with expected results. The developed relay and current transformer models are used to complete a detailed protection design for a sample power system. A small 230kV bulk-power transmission system is presented and modeled in the Simulink environment. A fault study is completed and current transformers are specified in accordance with IEEE standards. Bus and line protections are selected from the various implementations discussed in the report. The settings for all protection relays are developed in detail based on system analysis and the expert guidelines obtained from a wide literature review. The resulting protection design was tested in a systematic fashion and demonstrated to be effective.

Modeling and simulation of power system protection relays in a transmission-level application

This report presents the findings of an in-depth literature review on protective relaying. The project focuses on protection system practices which are relevant to transmission-level applications. Various implementations of differential, phase distance and ground distance relays were investigated and ultimately modeled in the Matlab Simulink environment. A further model for a saturable iron-core current transformer was also investigated and developed. These models were tested to ensure compliance with expected results. The developed relay and current transformer models are used to complete a detailed protection design for a sample power system. A small 230kV bulk-power transmission system is presented and modeled in the Simulink environment. A fault study is completed and current transformers are specified in accordance with IEEE standards. Bus and line protections are selected from the various implementations discussed in the report. The settings for all protection relays are developed in detail based on system analysis and the expert guidelines obtained from a wide literature review. The resulting protection design was tested in a systematic fashion and demonstrated to be effective.

Xenon Plasma Focused Ion Beam Milling for Obtaining Soft X-ray Transparent Samples

We employ xenon (Xe) plasma focused ion beam (PFIB) milling to obtain soft X-ray transparent windows out of bulk samples. The use of a Xe PFIB allows for the milling of thin windows (several 100 nm thick) with areas of the order of 100 µm × 100 µm into bulk substrates. In addition, we present an approach to empirically determine the transmission level of such windows during fabrication by correlating their electron and soft X-ray transparencies. We perform scanning transmission X-ray microscopy (STXM) imaging on a sample obtained by Xe PFIB milling to demonstrate the conceptual feasibility of the technique. Our thinning approach provides a fast and simplified method for facilitating soft X-ray transmission measurements of epitaxial samples and it can be applied to a variety of different sample systems and substrates that are otherwise not accessible.