Performance tradeoffs of dynamically controlled grid-connected inverters in low inertia power systems

摘要

Implementing frequency response using grid-connected inverters is one of thepopular proposed alternatives to mitigate the dynamic degradation experiencedin low inertia power systems. However, such solution faces several challengesas inverters do not intrinsically possess the natural response to powerfluctuations that synchronous generators have. Thus, to synthetically generatethis response, inverters need to take frequency measurements, which are usuallynoisy, and subsequently make changes in the output power, which are thereforedelayed. This paper explores the system-wide performance tradeoffs that arisewhen measurement noise, power disturbances, and delayed actions are consideredin the design of dynamic controllers for grid-connected inverters. Using arecently proposed dynamic droop (iDroop) control for grid-connected inverters,which is inspired by classical first order lead-lag compensation, we show thatthe sets of parameters that result in highest noise attenuation, powerdisturbance mitigation, and delay robustness do not necessarily have a commonintersection. In particular, lead compensation is desired in systems wherepower disturbances are the predominant source of degradation, while lagcompensation is a better alternative when the system is dominated by delays orfrequency noise. Our analysis further shows that iDroop can outperform thestandard droop alternative in both joint noise and disturbance mitigation, anddelay robustness.