Application and control for virtual synchronous generators

• Main Author: Guo, Yian
• Other Authors: Tang Yi
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/175597
• Institution: Nanyang Technological University

As the penetration of renewable energy sources increases year by year, power systems with a high proportion of renewable energy face a relative lack of inertia, posing new challenges to system stability. Virtual synchronous generators, emerging as a novel inverter control strategy in recent years, are gaining popularity due to their ability to provide inertial support to the system. VSGs, particularly their ability to offer essential frequency and voltage support, render them suitable for a wide array of applications. This includes their integration into renewable energy setups such as solar and wind power projects that lack storage capabilities, as well as their pivotal role in enhancing the reliability and flexibility of HVDC (High Voltage Direct Current) transmission systems. VSGs emerge as a cornerstone technology in ensuring grid stability and resilience, especially with the increasing penetration of intermittent renewable energy sources. In the quest to harness the full potential of VSG technology, this paper delves deep into the foundational principles that govern its operation. Starting with a detailed examination of the mechanical equations underlying synchronous motor rotors, it extends to a comprehensive study of speed regulator principles and their corresponding models. This meticulous analysis facilitates the derivation of a widely applicable second-order VSG control model. The paper doesn't stop at the theoretical formulation but proceeds to conduct an extensive characteristic analysis of the derived model, shedding light on its operational nuances. Further amplifying the practical relevance of this study, a detailed VSG model was meticulously constructed and tested using advanced simulation software. This phase of the research was instrumental in validating the VSG's operational efficacy in both isolated and grid-connected scenarios. Critical attributes such as the frequency-power droop characteristic, inertia response, and the generator's capability to support the grid frequency were closely examined. The findings from these simulation exercises provide compelling evidence of the VSG's value in maintaining grid stability, offering a promising solution to the challenges posed by the integration of renewable energy sources into the power grid. Continuing the exploration to align with real-world conditions more closely, the paper delves into the operation of two VSGs running in parallel. Initially, a small-signal model for the parallel operation of two inverters was developed. Through principled analysis, the causes behind active power oscillations under parallel operation conditions were deduced. Building on this foundational small-signal model, an adaptive parameter control strategy was proposed to mitigate these power oscillations. This novel control strategy leverages the dynamism of VSG parameters to counteract the destabilizing effects of power oscillations in a parallel VSG setup. It represents a significant advancement in managing the complexities associated with the parallel operation of VSGs, addressing the inherent challenges in synchronizing multiple power sources. The effectiveness of this control strategy was then rigorously tested using simulation models. These simulations played a crucial role in demonstrating the validity of the proposed approach, offering concrete evidence of its ability to stabilize power outputs and maintain operational harmony between parallel VSGs. This section of the study not only underscores the technical feasibility of the proposed control strategy but also highlights its practical applicability in enhancing the reliability and efficiency of VSG-operated power systems.