30 research outputs found
Plug-and-play Solvability of the Power Flow Equations for Interconnected DC Microgrids with Constant Power Loads
In this paper we study the DC power flow equations of a purely resistive DC
power grid which consists of interconnected DC microgrids with constant-power
loads. We present a condition on the power grid which guarantees the existence
of a solution to the power flow equations. In addition, we present a condition
for any microgrid in island mode which guarantees that the power grid remains
feasible upon interconnection. These conditions provide a method to determine
if a power grid remains feasible after the interconnection with a specific
microgrid with constant-power loads. Although the presented condition are more
conservative than existing conditions in the literature, its novelty lies in
its plug-and-play property. That is, the condition gives a restriction on the
to-be-connected microgrid, but does not impose more restrictions on the rest of
the power grid.Comment: 8 pages, 2 figures, submitted to IEEE Conference on Decision and
Control 201
Nonlinear spacing policies for vehicle platoons:A geometric approach to decentralized control
In this paper a decentralized approach to the platooning problem with nonlinear spacing policies is considered. A predecessor–follower control structure is presented in which a vehicle is responsible for tracking of a desired spacing policy with respect to its predecessor, regardless of the control action of the latter. From the perspective of geometric control theory, we state necessary and sufficient conditions for the existence of decentralized controllers that guarantee tracking and asymptotic stabilization of a general nonlinear spacing policy. Moreover, all nonlinear spacing policies for which there exists a decentralized state feedback controller that achieves asymptotic tracking are characterized. It is shown that string stability is a consequence of the choice of spacing policy and sufficient conditions for a spacing policy to imply string stability are given. As an example, we fully characterize all state feedback controllers that achieve the control goals for a given nonlinear spacing policy, guaranteeing asymptotic tracking for a heterogeneous platoon. The results are illustrated through simulations
On stabilizability of switched differential algebraic equations
This paper considers stabilizability of switched differential algebraic equations (DAEs). We first introduce the notion of interval stabilizability and show that under a certain uniformity assumption, stabilizability can be concluded from interval stabilizability. A geometric approach is taken to find necessary and sufficient conditions for interval stabilizability. This geometric approach can also be utilized to derive a novel characterization of controllability
DC power grids with constant-power loads—Part II:Nonnegative power demands, conditions for feasibility, and high-voltage solutions
In this two-part paper we develop a unifying framework for the analysis of the feasibility of the power flow equations for DC power grids with constant-power loads. Part II of this paper explores further implications of the results in Part I. We present a necessary and sufficient LMI condition for the feasibility of a vector of power demands (under small perturbation), which extends a necessary condition in the literature. The alternatives of these LMI conditions are also included. In addition we refine these LMI conditions to obtain a necessary and sufficient condition for the feasibility of nonnegative power demands, which allows for an alternative approach to determine power flow feasibility. Moreover, we prove two novel sufficient conditions, which generalize known sufficient conditions for power flow feasibility in the literature. Finally, we prove that the unique long-term voltage semi-stable operating point associated to a feasible vector of power demands is a strict high-voltage solution. A parametrization of such operating points, which is dual to the parametrization in Part I, is obtained, as well as a parametrization of the boundary of the set of feasible power demands