Adaptive Backstepping-based H∞ Robust controller for Photovoltaic Grid-connected Inverter

To improve the robustness and stability of the photovoltaic grid-connected inverter system, a nonlinear backstepping-based H∞ controller is proposed. A generic dynamical model of grid-connected inverters is built with the consideration of uncertain parameters and external disturbances that cannot be accurately measured. According to this, the backstepping H∞ controller is designed by combining techniques of adaptive backstepping control and L2-gain robust control. The Lyapunov function is used to design the backstepping controller, and the dissipative inequality is recursively designed. The storage functions of the DC capacitor voltage and grid current are constructed, respectively, and the nonlinear H∞ controller and the parameter update law are obtained. Experimental results show that the proposed controller has the advantage of strong robustness to parameter variations and external disturbances. The proposed controller can also accurately track the references to meet the requirements of high-performance control of grid-connected inverters

Model-free predictive H∞ control for grid-connected solar power generation systems

A novel model-free predictive mixed-sensitivity H∞control scheme is proposed and applied to grid-connected solarpower generation systems. The predictive sensitivity and thepredictive complementary sensitivity are defined based on the predictive model. The model-free predictive mixed-sensitivity H∞ controller is derived from input/output measurements to achieve an optimal predictive mixed-sensitivity performance using a maxmin optimization method. Then, a simulation system for solar power generation systems is established using SimPowerSystems. Finally, the simulations are conduced to show the effectiveness of the proposed model-free controller, which out performs the conventional proportional-integral and model-free linear quadratic Gaussian controllers in the tracking performance and the robustness of solar power generation systems

Model-free predictive H∞ control for grid-connected solar power generation systems

A novel model-free predictive mixed-sensitivity H∞control scheme is proposed and applied to grid-connected solarpower generation systems. The predictive sensitivity and thepredictive complementary sensitivity are defined based on the predictive model. The model-free predictive mixed-sensitivity H∞ controller is derived from input/output measurements to achieve an optimal predictive mixed-sensitivity performance using a maxmin optimization method. Then, a simulation system for solar power generation systems is established using SimPowerSystems. Finally, the simulations are conduced to show the effectiveness of the proposed model-free controller, which out performs the conventional proportional-integral and model-free linear quadratic Gaussian controllers in the tracking performance and the robustness of solar power generation systems

Frequency regulation for power systems with renewable energy sources

Both the increasing penetration of renewable sources and their participation in the production of power in the electrical system require a more comprehensive analysis of the dynamic behavior of the grid frequency regulation structure. In this sense, this work presents the use of Control Sensitivity Functions to describe the dynamical characteristics of both primary and secondary control loops in frequency regulation. Bode plots are employed as a visualization and analysis tool. These sensitivity functions are applied to study the behavior of the power system with the contribution of wind turbines through the inertia emulation techniques. In this regard, the effects of inertia variations in frequency control are addressed for power systems under the integration of wind units. The transfer functions of the system are obtained starting from a linearized wind turbine model. The mathematical relationships are formulated to analyze the sensitivity and stability regarding inertia coefficient H. These expressions are then verified through simulation of several cases under different stability conditions and disturbances in wind speed and loadResumen: Tanto la creciente penetración de fuentes renovables de energía como su participación en el despacho de suministro energético en el sistema de potencia requiere un análisis completo del comportamiento dinámico de la estructura de regulación de frecuencia. En este sentido, esta tesis presenta el uso de las Funciones de Sensibilidad de Control para describir las características dinámicas de los lazos primario y secundario de regulación de frecuencia en sistemas de potencia, utilizando diagramas de Bode como herramienta de visualización y análisis. Estas funciones de sensibilidad se aplican en el estudio del comportamiento dinámico de la regulación en frecuencia con contribuciones de turbinas eólicas a través de las técnicas de emulación inercial. Bajo este escenario, los efectos de las incertidumbres o variaciones en la inercia son estudiados desde la integración de las turbinas eólicas en la estructura de control. Partiendo de una representación lineal del sistema, se proponen las formulaciones matemáticas necesarias para analizar la sensibilidad y la estabilidad del sistema con respecto a los cambios en la inercia. Estas expresiones se verifican a través de simulación de varios casos bajo diferentes condiciones de estabilidad y perturbaciones en la velocidad del viento y en la carga del sistemaDoctorad