Modeling and Control of High-Voltage Direct-Current Transmission Systems: From Theory to Practice and Back

The problem of modeling and control of multi-terminal high-voltage direct-current transmission systems is addressed in this paper, which contains five main contributions. First, to propose a unified, physically motivated, modeling framework - based on port-Hamiltonian representations - of the various network topologies used in this application. Second, to prove that the system can be globally asymptotically stabilized with a decentralized PI control, that exploits its passivity properties. Close connections between the proposed PI and the popular Akagi's PQ instantaneous power method are also established. Third, to reveal the transient performance limitations of the proposed controller that, interestingly, is shown to be intrinsic to PI passivity-based control. Fourth, motivated by the latter, an outer-loop that overcomes the aforementioned limitations is proposed. The performance limitation of the PI, and its drastic improvement using outer-loop controls, are verified via simulations on a three-terminals benchmark example. A final contribution is a novel formulation of the power flow equations for the centralized references calculation

Detection of Broken Bars in Induction Motors Using an Extended Kalman Filter for Rotor Resistance Sensorless Estimation

International audienceThis paper deals with the broken bars detection in induction motors. The hypothesis on which detection is based is that the apparent rotor resistance of an induction motor will increase when a rotor bar breaks. To detect broken bars, measurements of stator voltages and currents are processed by an Extended Kalman Filter for the speed and rotor resistance simultaneous estimation. In particular, rotor resistance is estimated and compared with its nominal value to detect broken bars. In the proposed extended Kalman Filter approach, the state covariance matrix is adequacy weighted leading to a better states estimation dynamic. Its main advantage is the correct rotor resistance estimation even for an unloaded induction motor. As part of this estimation process, it is necessary to compensate for the thermal variation in the rotor resistance. Computer simulations, carried out for a 4-kW four-pole squirrel cage induction motor, provide an encouraging validation of the proposed sensorless broken bars detection technique

Optimisation des Pertes par Commutation dans un Convertisseur Modulaire Multiniveaux (MMC)

International audienceLes pertes dans une liaison à courant continu àhaute tension sont un facteur pénalisant (4000 €/kW sur une duréede 30 ans). L’inconvénient vient des structures de type Onduleurde tension qui ont des pertes élevées (1.8%) relativement auxstructures à base de thyristors. L’arrivée des convertisseurs detype Modulaires Multiniveaux (MMC) a permis de réduire cespertes à 1%. Cet avantage permet d’envisager une forte utilisationde cette structure dans des applications HVDC. Le but de cetravail est d’étudier le contrôle bas niveau de ce convertisseur quicorrespond au choix des sous-modules à utiliser et à l’équilibragedes condensateurs afin de minimiser la fréquence de commutation.En se focalisant sur un contrôle de type ondulation des tensions dessous modules, une amélioration a été apportée via une réductionde la fréquence de commutation moyenne de ces sous-modules. Dessimulations sous MATLAB/Simulink ont été conduites et ontpermis de valider la méthode proposée

A Metric Observer for Induction Motors Control

This paper deals with metric observer application for induction motors. Firstly, assuming that stator currents and speed are measured, a metric observer is designed to estimate the rotor fluxes. Secondly, assuming that only stator currents are measured, another metric observer is derived to estimate rotor fluxes and speed. The proposed observer validity is checked throughout simulations on a 4 kW induction motor drive

Control of HVDC transmission systems: From theory to practice and back

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Enhanced LMI-based Damping Control in Power Networks through a High Voltage Direct Current Line

Large interconnected power networks are arguably some of the most complicated man-made systems to understand and characterize. This becomes even more complicated due to the surge of renewables that are connected (possible via HVDC lines) to the network. Faults, such as the tripping of an electricity line, can easily occur in a network, which can cause undesired oscillatory behaviour. This paper proposes an output-feedback controller that aims at diminishing these oscillations. The presented controller consists of a state-feedback gain and a Kalman filter and is tuned by employing an in this work identified model. The proposed controller ensures a lower bound on the closed-loop damping coefficients of the network

MODULE FOR CONTROLLING THE INTERNAL ENERGY OF A CONVERTER

The invention relates to a multilevel modular converter (10) including a control module (12) for regulating the internal energy stored in the capacitors of the submodules of a half arm of the converter, the control module being capable of keeping the internal energy below an upper limit and/or above a lower limit, by using parameters measured on the DC electrical power supply network (110) and on the AC electrical power supply network (120) as well as operating power setpoints of the converter

MODULE FOR CONTROLLING THE INTERNAL ENERGY OF A CONVERTER

The invention relates to a multilevel modular converter (10) including a control module (12) for regulating the internal energy stored in the capacitors of the submodules of a half arm of the converter, the control module being capable of keeping the internal energy below an upper limit and/or above a lower limit, by using parameters measured on the DC electrical power supply network (110) and on the AC electrical power supply network (120) as well as operating power setpoints of the converter