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A novel ride-through approach for matrix converters in adjustable speed drives is presented. The input capacitors are utilized to transfer energy from the spinning inertia of the motor to support the motor flux during grid fault events. The addition of three bidirection switches is required to isolate the input filter capacitors from the collapsed grid voltages. The addition of input switches, a ride-through vector control strategy, and post fault reconnection logic are shown to enable ride-through of many cycle faults without the use of an additional energy storage device. In this paper, the control and reconnect strategies are discussed followed by simulations of the system and the presentation of experimental results. Through a short review of power quality assessments, it is shown that these improvements allow matrix converter-based adjustable speed drives to operate in a majority of real world fault situations.

This report reflects the results of U.S. Department of Energy's (DOE) Grid Modernization project 0074 "Models and methods for assessing the value of HVDC [high-voltage direct current] and MTDC [multiterminal direct current] technologies in modern power grids." The work was done by the Pacific Northwest National Laboratory (PNNL) and Oak Ridge National Laboratory (ORNL) in cooperation with Mid-Continent Independent System Operator (MISO) and Siemens. The main motivation of this study was to show the benefit of using direct current (DC) systems larger than those in existence today as they overlap with the alternating current (AC) systems. Proper use of their flexibility in terms of active/reactive power control and fast response can provide much-needed services to the grid at the same time as moving large blocks of energy to take advantage of cost diversity. Ultimately, the project's success will enable decision-makers and investors to make well-informed decisions regarding this use of DC systems. This project showed the technical feasibility of HVDC macrogrid for frequency control and congestion relief in addition to bulk power transfers. Industryestablished models for commonly used technologies were employed, along with high-fidelity models for recently developed HVDC converter technologies; like the modular multilevel converters (MMCs), and voltage source converters (VSC). New detailed models for General Electric Positive Sequence Load Flow (GE PSLF) and Siemens's Power System Simulator (PSS®E), widely used analysis programs, were for the first time adapted to include at the same time both Western Electricity Coordinating Council (WECC) and Eastern Interconnection (EI), the two largest North American interconnections. The high-fidelity models and their control were developed in detail for MMC system and extended to HVDC systems in point-to-point and in three-node multi-terminal configurations. Using a continental-level mixed AC-DC grid model, an HVDC macrogrid power flow and transient stability models, the results showed that the HVDC macrogrid relieved congestion and mitigated loop flows in AC networks, and provided up to 24% improvement in frequency responses. These are realistic studies, based on the 2025 heavy summer Western Interconnection (WI) planning model and EI multiregional modeling working group (MMWG) 2026 summer peak cases. This work developed high-fidelity models and simulation algorithms to understand the dynamics of MMC systems. The developed models and simulation algorithms are up to 25 times faster than the existing algorithms. Control algorithms for high-fidelity models were designed and tested for point-to-point and multi-terminal configurations. The multi-terminal configuration was tested connecting simplified models of EI, WI, and Electric Reliability Council of Texas (ERCOT). The developed models showed up to 45% improvement in frequency response with the connection of all the three asynchronous interconnections in the United States using fast and advanced DC technologies like the multi-t...

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