Arnau Dòria-Cerezo

Power Flow Control of a Doubly-Fed Induction Machine Coupled to a Flywheel*

We consider a doubly-fed induction machine-controlled through the rotor voltage and connected to a variable local load-that acts as an energy-switching device between a local prime mover (a flywheel) and the electrical power network. The control objective is to optimally regulate the power flow, and this is achieved by commuting between two different steady-state regimes. The marginal stability of the zero dynamics of the system hampers its control via feedback linearization. Instead, we apply the energy-based interconnection and damping assignment passivity-based control technique, which does not require stable invertibility. It is shown that the partial differential equation that appears in this method can be obviated fixing the desired closed-loop total energy and adding new terms to the interconnection structure. Furthermore, to obtain a globally defined control law we introduce a state-dependent damping term that has the nice interpretation of effectively decoupling the electrical and mechanical parts of the system. This results in a globally asymptotically stabilizing controller parameterized by two degrees of freedom, which can be used to implement the power management policy. The controller is simulated and shown to work satisfactorily for various realistic load changes.

Simultaneous interconnection and damping assignment passivity-based control: the induction machine case study

We argue in this article that the standard two-stage procedure used in interconnection and damping assignment passivity-based control (IDA–PBC)–consisting of splitting the control action into the sum of energy-shaping and damping injection terms–is not without loss of generality, and effectively reduces the set of systems that can be stabilised with IDA–PBC. To overcome this problem we carry out, simultaneously, both stages and refer to this variation of the method as SIDA–PBC. To illustrate the application of SIDA–PBC we consider the practically important example given by the control problem of the induction machine. First, we show that torque and rotor flux regulation of the induction motor cannot be solved with two stage IDA–PBC. It is, however, solvable with SIDA–PBC. Second, we prove that with SIDA–PBC we can shape the total energy of the full (electrical and mechanical) dynamics of a doubly-fed induction generator used in power flow regulation tasks, while with two stage IDA–PBC only the electrical energy can be shaped. Simulation results of these examples are presented to illustrate the performance improvement obtained with SIDA–PBC.

Sliding Mode Control of a Stand-Alone Wound Rotor Synchronous Generator

This paper presents a sliding mode control for a wound rotor synchronous machine acting as an isolated generator. The standard dq model of the machine is connected to a resistive load. A switching function is defined in order to fulfill control objectives, and the ideal sliding dynamics is proved to be stable. From the desired surface, the standard sliding methodology is applied to obtain a robust and very simple controller. Numerical simulations and experimental results validate the control law and show good performance and a fast response to load and reference changes.

Port-Hamiltonian Formulation of Systems With Memory

In this paper, we consider memristors, meminductors, and memcapacitors and their properties as port-Hamiltonian systems. The port-Hamiltonian formalism naturally arises from network modeling of physical systems in a variety of domains. Exposing the relation between the energy storage, dissipation, and interconnection structure, this framework underscores the physics of the system. One of the strong aspects of the port-Hamiltonian formalism is that a power-preserving interconnection between port-Hamiltonian systems results in another port-Hamiltonian system with composite energy, dissipation, and interconnection structure. This feature can advantageously be used to model, analyze, and simulate networks consisting of complex interconnections of both conventional and memory circuit elements. Furthermore, the port-Hamiltonian formalism naturally extends the fundamental properties of the memory elements beyond the realm of electrical circuits.

IDA-PBC controller for a bidirectional power flow full-bridge rectifier

A controller able to support bidirectional power flow in a full-bridge rectifier with boost-like topology is obtained. The controller is computed using port Hamiltonian passivity techniques for a suitable generalized state space averaging truncation of the system, which transforms the control objectives, namely constant output voltage dc-bus and unity input power factor, into a regulation problem. Simulation results for the full system show the correctness of the simplifi-cations introduced to obtain the controller.

Energy-based modelling and simulation of the interconnection of a back-to-back converter and a doubly-fed induction machine

This paper describes the port interconnection of two subsystems: a power electronics subsystem (a back-to-back AC/AC converter (B2B), coupled to a phase of the power grid), and an electromechanical subsystem (a doubly-fed induction machine (DFIM). The B2B is a variable structure system (VSS), due to the presence of control-actuated switches; however, from a modelling and simulation, as well as a control-design, point of view, it is sensible to consider modulated transformers (MTF in the bond graph language) instead of the pairs of complementary switches. The port-Hamiltonian models of both subsystems are presented and, using a power-preserving interconnection, the Hamiltonian description of the whole system is obtained; detailed bond graphs of all subsystems and the complete system are also provided. Using passivity-based controllers computed in the Hamiltonian formalism for both subsystems, the whole model is simulated; simulations are run to test the correctness and efficiency of the Hamiltonian network modelling approach used in this work

A Robustly Stable PI Controller For The Doubly-Fed Induction Machine

In this paper we propose a new control scheme for the doubly-fed induction machine (DFIM) that offers significant advantages, and is considerably simpler, than the classical vector control method. In contrast with the latter, where the DFIM is represented in a stator flux-oriented frame, we propose here a model with orientation of the stator voltage. This allows for an easy decomposition of the active and reactive powers on the stator side and their regulation - acting on the rotor voltage - via stator current control. Our main contribution is the proof that a linear PI control around the stator currents ensures global stability for a feedback linearized DFIM, provided the gains are suitably selected. The feedback linearization stage requires only measurement of the rotor and stator currents, hence is easily implementable. Finally, an outer loop control for the mechanical speed is introduced. The complete control system is tested both in simulations and experiments, showing good transient performance and robustness properties

Simultaneous Interconnection and Damping Assignment Passivity-Based Control: Two Practical Examples

Passivity-based control (PBC) is a generic name given to a family of controller design techniques that achieves system stabilization via the route of passivation, that is, rendering the closed-loop system passive with a desired storage function (that usually qualifies as a Lyapunov function for the stability analysis.) If the passivity property turns out to be output strict, with an output signal with respect to which the system is detectable, then asymptotic stability is ensured. See the monographs [5, 12], and [6] for a recent survey.

Control of a Stand-Alone Wound Rotor Synchronous Generator: Two Sliding Mode Approaches via Regulation of the d-Voltage Component

In this brief two sliding mode control alternatives to regulate the stator voltage amplitude for a stand alone wound rotor synchronous generator are presented. Both controllers use the stator voltage -component error in the sliding surface. In a first case an outer proportional-integral (PI) loop controller is added to provide the proper d-voltage component reference. The second approach consists in extending the dynamic system to include the integral term as state variable and to modify the former sliding surface by adding this new state. Finally, both simulations and experimental results validates the proposed algorithms.

Root locus rules for polynomials with complex coefficients

Applications were found recently where the analysis of dynamic systems with a special structure could be simplified considerably by transforming them into equivalent systems having complex coefficients and half the number of poles. The design of controllers for such systems can be simplified in the complex representation, but requires techniques suitable for systems with complex coefficients. In the paper, the extension of the classical root locus method to systems with complex coefficients is presented. The results are applied with some advantages to a three-phase controlled rectifier.