Assessing the impact of voltage control variants in synchronous generators on interactions with grid-forming inverters
Graybrook-Paul, Ethan (2025)
Diplomityö
2025
School of Energy Systems, Energiatekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe20251124110815
https://urn.fi/URN:NBN:fi-fe20251124110815
Tiivistelmä
The increasing capacity of renewable electricity generation has resulted in more grid-connected grid following inverters and fewer synchronous generators, which has been shown to erode network stability. Grid forming inverters are a potential solution as they can bolster network stability by emulating the grid supporting characteristics of synchronous machines, however their interactions with synchronous generators particularly at high penetration has been shown to be potentially destabilising for the grid.
This thesis explores the effect on excitation controls in these interactions, particularly how the controller type, be that proportional (P), proportional-integral (PI), or proportional-inte\-gral-derivative (PID), changes the small-signal stability of a coupled synchronous generator and grid forming inverter. An analytical model of a 1.4 GVA synchronous generator was derived and used to tune a PI and PID controller. The small-signal stability was then assessed via electromagnetic transient (EMT) simulations.
It was found that, while the system remained stable at nominal operating conditions, when system robustness was reduced the PI and PID controllers introduced instability phenomena which were not present in the P type controller. Introducing a power-system stabiliser (PSS) was found to be effective in mitigating instability. Additional factors related to the droop settings of the generator and inverter were tested and found to also impact stability.
This thesis explores the effect on excitation controls in these interactions, particularly how the controller type, be that proportional (P), proportional-integral (PI), or proportional-inte\-gral-derivative (PID), changes the small-signal stability of a coupled synchronous generator and grid forming inverter. An analytical model of a 1.4 GVA synchronous generator was derived and used to tune a PI and PID controller. The small-signal stability was then assessed via electromagnetic transient (EMT) simulations.
It was found that, while the system remained stable at nominal operating conditions, when system robustness was reduced the PI and PID controllers introduced instability phenomena which were not present in the P type controller. Introducing a power-system stabiliser (PSS) was found to be effective in mitigating instability. Additional factors related to the droop settings of the generator and inverter were tested and found to also impact stability.