18 research outputs found
Power-balancing dual-port grid-forming power converter control for renewable integration and hybrid AC/DC power systems
In this work, we investigate grid-forming (GFM) control for dc/ac power
converters in emerging power systems that contain ac and dc networks, renewable
generation, and conventional generation. We propose a novel power-balancing GFM
control strategy that simultaneously forms the converter ac and dc voltage
(i.e., dual-port GFM), unifies standard grid-following (GFL) and GFM functions,
and is backwards compatible with conventional machine-based generation.
Notably, in contrast to state-of-the-art control architectures that use a mix
of grid-forming and grid-following control, dual-port GFM control can be used
independently of the converter power source or network configuration. Our main
contribution are stability conditions that cover emerging hybrid ac/dc networks
as well as machines and converters with and without controlled power source,
that only require knowledge of the system topology. Finally, a detailed case
study is used to illustrate and validate the results
Universal dual-port grid-forming control: bridging the gap between grid-forming and grid-following control
We study a dual-port grid-forming (GFM) control for power systems containing
ac and dc transmission, converter-interfaced generation and energy storage, and
legacy generation. To operate such a system and provide standard services,
state-of-the-art control architectures i) require assigning grid-following
(GFL) and GFM controls to different converters, and ii) result in highly
complex system dynamics. In contrast, dual-port GFM control (i) subsumes
standard functions of GFM and GFL controls in a simple controller, ii) can be
applied to a wide range of emerging technologies independently of the network
configuration, and iii) significantly reduces system complexity. In this work,
we provide i) an end-to-end modeling framework that allows to model complex
topologies through composition of reduced-order device models, ii) an in-depth
discussion of universal dual-port GFM control for emerging power systems, and
iii) end-to-end stability conditions that cover a wide range of network
topologies, emerging technologies, and legacy technologies. Finally, we
validate our findings in a detailed case study
Time-varying Projected Dynamical Systems with Applications to Feedback Optimization of Power Systems
This paper is concerned with the study of continuous-time, non-smooth
dynamical systems which arise in the context of time-varying non-convex
optimization problems, as for example the feedback-based optimization of power
systems. We generalize the notion of projected dynamical systems to
time-varying, possibly non-regular, domains and derive conditions for the
existence of so-called Krasovskii solutions. The key insight is that for
trajectories to exist, informally, the time-varying domain can only contract at
a bounded rate whereas it may expand discontinuously. This condition is met, in
particular, by feasible sets delimited via piecewise differentiable functions
under appropriate constraint qualifications. To illustrate the necessity and
usefulness of such a general framework, we consider a simple yet insightful
power system example, and we discuss the implications of the proposed
conditions for the design of feedback optimization schemes