Sliding-Mode Perturbation Observer-Based Sliding-Mode Control for VSC-HVDC Systems

This chapter develops a sliding-mode perturbation observer-based sliding-mode control (POSMC) scheme for voltage source converter-based high voltage direct current (VSC-HVDC) systems. The combinatorial effect of nonlinearities, parameter uncertainties, unmodeled dynamics, and time-varying external disturbances is aggregated into a perturbation, which is estimated online by a sliding-mode state and perturbation observer (SMSPO). POSMC does not require an accurate VSC-HVDC system model and only the reactive power and DC voltage at the rectifier side while reactive and active powers at the inverter side need to be measured. Additionally, a considerable robustness can be provided through the real-time compensation of the perturbation, in which the upper bound of perturbation is replaced by the real-time estimation of the perturbation, such that the over-conservativeness of conventional sliding-mode control (SMC) can be effectively reduced. Four case studies are carried out on the VSC-HVDC system, such as active and reactive power tracking, AC bus fault, system parameter uncertainties, and weak AC gird connection. Simulation results verify its advantages over vector control and feedback linearization sliding-mode control. Then, a dSPACE-based hardware-in-the-loop (HIL) test is undertaken to validate the implementation feasibility of the proposed approach

Modélisation et commande non linéaire des hydroliennes couplées à un réseau électrique

This thesis develops nonlinear and robust control strategies in order to ensure a successful connection of marine turbine systems into grid. In addition, it is a question to examine in simulation and practice the dynamic behavior of controlled marine turbine systems under severe perturbations. Firstly, we have modeled all production chain elements of marine turbine system. Secondly, we have proposed three nonlinear control strategies ; one for marine turbine system single machine connected to infinite bus and the both others for two multimachine electrical networks. The developed strategies control stability is proven mathematically by using Lyapunov method and one specific property of variable structure. These strategies control particularity is the two outputs regulation (terminal voltage and frequency) trough a single input (synchronous machine excitation). Finally, simulation results under mechanical and electrical perturbations are presented in order to highlight the robustness qualities of the proposed controllers compared to nonlinear controller CNL and classical AVR-PSS. In view of industrial applications, the proposed control for marine turbine single machine system is implemented on experimental bench. The obtained practical results under hard perturbations are very satisfactory. These results are used to realize a comparative study between the proposed control, the CNL and the AVR-PSS.L’objectif de cette thèse est de développer des stratégies de commande non linéaire et robuste afin d’assurer une connexion avec succès des systèmes hydroliens dans un réseau électrique de forte puissance. Il s’agira en plus, d’étudier en simulation et en pratique le comportement dynamique de ses systèmes hydroliens commandés suite à des perturbations sévères. Dans un premier temps, nous nous sommes intéressés à la modélisation de tous les éléments de la chaine de production d’énergie hydrolienne, en partant de la marée jusqu’à la génératrice synchrone. Dans un second temps, nous avons proposé trois lois de commande non linéaire ; une pour un système hydrolien mono machine et les deux autres pour deux types de réseau électrique multi-machine. La stabilité de ces lois de commandes est prouvée en utilisant la méthode de Lyapunov et les propriétés spécifiques à la structure variable. La particularité de ces lois de commandes est qu’elles régulent simultanément la tension terminale et la fréquence en agissant uniquement sur l’excitation de la génératrice synchrone. Finalement, nous avons étudié en simulation le comportement dynamique des systèmes hydroliens commandés et les résultats obtenus sous perturbations électrique et mécanique ont montré l’efficacité de la commande proposée par rapport aux commandes CNL et AVR-PSS. Dans un souci de valider pratiquement ces résultats de simulation, la commande non linéaire proposée pour le système hydrolien mono machine est implantée sur un banc d’essai. Les résultats satisfaisants obtenus sous perturbations soutenues sont ensuite comparés à ceux obtenus pratiquement avec les commandes, CNL et AVR-PSS

Perturbation Observer based Adaptive Passive Control and Applications for VSC-HVDC Systems and FACTS Devices

The technology of voltage source converter based high voltage direct current (VSC-HVDC) system and devices used in flexible AC transmission systems (FACTS) has evolved significantly over the past two decades. It is used to effectively enhance power system stability. One of the important issues is how to design an applicable nonlinear adaptive controller for these devices to effectively handle the system nonlinearities and uncertainties. Passive control (PC) has been proposed for the control of nonlinear systems based on Lyapunov theory, which has the potential to improve the system damping as the beneficial system nonlinearities are remained instead of being fully cancelled. However, PC is not applicable in practice as it requires an accurate system model. Adaptive passive control (APC) and robust passive control (RPC) have been developed to handle some specific type of system uncertainties based on strict assumptions on system structure and uncertainty. However, their applications are limited as various system uncertainties exist. This thesis aims to develop a perturbation observer based adaptive passive control (POAPC) to make PC applicable in practice. The combinatorial effect of system nonlinearities, parameter uncertainties, unmodelled dynamics and time-varying external disturbances is aggregated into a perturbation, which is estimated by a perturbation observer (PO). The proposed approach does not require an accurate system model and can handle various system uncertainties. POAPC is applied to two-terminal VSC-HVDC systems to handle various system uncertainties. The VSC-HVDC system model is firstly developed, the proposed controller can inject an extra system damping and only the measurement of direct current (DC) voltage, active and reactive power is needed. The effectiveness ofPOAPC is verified by simulation in comparison with that of passive control (PC) and proportional-integral (PI) control. Moreover, a hardware experiment is carried out to verify its implementation feasibility and applicability. A passive controller is designed for multi-terminal VSC-HVDC (VSC-MTDC) systems via energy shaping, in which the dynamics related to the active power, reactive power, and DC cable voltage is transformed into an output strictly passive form. Then the remained internal dynamics related to DC cable current and common DC voltage is proved to be asymptotically stable in the context of Lyapunov criterion. PC is applied on a four-terminal VSC-MTDC system under eight cases to evaluate its control performance. POAPC is developed on the VSC-MTDC system to maintain a consistent control performance under different operating points and provide a significant robustness to parameter uncertainties, together with other unmodelled dynamics and time-varying external disturbances. Simulation results are provided to evaluate the control performance of POAPC in comparison to that of PI control and PC. Perturbation observer based coordinated adaptive passive control (POCAPC) is proposed for excitation controller (EC) and FACTS controller on both single machine infinite bus (SMIB) systems and multi-machine power systems. Only the range of control Lyapunov function (CLF) is needed and the dependence of an accurate system model can be partially reduced, thus POCAPC can be easily applied to multi-machine power systems. Its control performance is compared with that of conventional proportional-integral-derivative and lead-lag (PID+LL) control, coordinated passive control (CPC) and coordinated adaptive passive control (CAPC) on both an SMIB system and a three-machine power system by simulation. Then a hardware-in-the-loop (HIL) test is undertaken to verify the implementation feasibility of the proposed controller