Dynamic Droop Control in Microgrid for Stability Enhancement Considering RES Variation

Abstract—In this paper, small signal stability analysis of a hybrid Microgrid (MG) considering RES variations is addressed. As wind speed or solar irradiance fluctuates, active power output from DGs might vary significantly. Hence, the power sharing scheme would change considerably. Dynamic droop-gain control is proposed to deal with the RES change and maintain the stability of MG. The proposed control method provides adjustable power sharing strategies to manage RES fluctuation and ensure frequency and voltage regulation of each DGs. Eigenvalues analysis and time domain simulation suggest that at high wind speed and solar irradiance the damping ratio of critical modes and dynamic performance of DG units defer significantly. As the dynamic droop controller implemented, the damping performance and stability margin of the hybrid MG were improved in different operating condition, ensuring stable MG operation in most of RES conditions. Keywords—Microgrid, RES variations, variable droop, power sharing, small signal stability

“Estrategia de control robusto descentralizado para una micro-red aislada con generación distribuida acoplada para mejorar la estabilidad de voltaje”

El constante avance de la tecnología requiere una gran cantidad de energía, por ello se ha propuesto la inclusión de fuentes de energía renovable (RES) cerca de los centros de carga. Estas RES son implementadas también en sectores donde el sistema eléctrico convencional no es capaz de llegar, de esta manera se garantiza el abastecimiento de energía eléctrica a toda la población. Sin embargo, la implementación de estos nuevos sistemas implica retos de control para que su funcionamiento sea correcto, indiferente que la Micro-red funcione de forma conectada o aislada a la red convencional. Este trabajo presenta una novedosa estrategia de control de Micro-redes aisladas, basado en el control jerárquico y control droop modificado. Esta estrategia robusta permite mejorar la estabilidad de voltaje y su comportamiento transitorio. Se implementa una Micro-red de referencia con dos fuentes fotovoltaicas con valores nominales. Lo que permite verificar el desempeño de la estrategia propuesta comparando con un controlador PI convencional.Technological advances demand a huge amount of electricity, therefore Renewable Energy Resources (RES) must be near the electrical demand is huge, in addition they are implemented in rural places, where electric utility is not able to provide the service. However, the implementation of these new systems implies facing new challenges for the correct operation of Microgrid connected or islanded from the conventional system. This research presents a novel control strategy for islanded Microgrids, based on hierarchical control and modified droop control. The robust control strategy presented allows stability voltage improvement and its transient behavior. Which subscribes to verify the performance of the proposed strategy compared with a conventional PI controller

Estrategia de control robusto descentralizado para una micro-red aislada con generación distribuida acoplada para mejorar la estabilidad de voltaje.

El paper presenta una novedosa estrategia de control de Micro-redes aisladas, basado en el control jerárquico y control droop modificado. Esta estrategia robusta permite mejorar la estabilidad de voltaje y su comportamiento transitorio. Se implementa una Micro-red de referencia con dos fuentes fotovoltaicas con valores nominales. Lo que permite verificar el desempeño de la estrategia propuesta comparando con un controlador PI convencional. El constante avance de la tecnología requiere una gran cantidad de energía, por ello se ha propuesto la inclusión de fuentes de energía renovable (RES) cerca de los centros de carga.  Estas RES son implementadas también en sectores donde el sistema eléctrico convencional no es capaz de llegar, de esta manera se garantiza el abastecimiento de energía eléctrica a toda la población. Sin embargo, la implementación de estos nuevos sistemas implica retos de control para que su funcionamiento sea correcto, indiferente que la Micro-red funcione de forma conectada o aislada a la red convencional

Modeling and Analyzing of Inverters for Controlling Voltage and Frequency in an Islanded Microgrid

Recently, the growth of inverter-based generations (IBGs) like solar photovoltaic (PV) and wind turbine generators in the form of microgrids (MGs) has been increasing. However, control of voltage and frequency becomes a challenging task for MGs especially when they operate in an islanded mode, due to the inherent low-inertia feature of IBGs compared to a grid-tied mode where there is a grid support. This thesis deals with modeling and analyzing of inverters capable of controlling voltage and frequency through external conventional droop control for the islanded operation of MG. In this thesis, a state space model is developed for a voltage source inverter with droop control. Moreover, non-linear models for the inverters in single and parallel cases with droop control are developed and the results are verified in different load scenarios. The results show a good performance of the projected control, both in the isolated operation of an inverter supplying a load, and in the parallel operation of isolated inverters, where there is power sharing to properly feed the load. MATLAB/Simulink environment is used for the work

Dynamic Droop Control in Microgrid for Stability Enhancement Considering RES Variation

In this paper, small signal stability analysis of a hybrid Microgrid (MG) considering RES variations is addressed. As wind speed or solar irradiance fluctuates, active power output from DGs might vary significantly. Hence, the power sharing scheme would change considerably. Dynamic droop-gain control is proposed to deal with the RES change and maintain the stability of MG. The proposed control method provides adjustable power sharing strategies to manage RES fluctuation and ensure frequency and voltage regulation of each DGs. Eigenvalues analysis and time domain simulation suggest that at high wind speed and solar irradiance the damping ratio of critical modes and dynamic performance of DG units defer significantly. As the dynamic droop controller implemented, the damping performance and stability margin of the hybrid MG were improved in different operating condition, ensuring stable MG operation in most of RES conditions