Frequency Stability Improvement in Weak Grids by Storage Systems

Author(s):  
Gianpaolo Vitale
Author(s):  
Ilker Durukan ◽  
Stephen Ekwaro-Osire ◽  
Stephen B. Bayne

Most recent grid codes require wind turbines to contribute to the recovery of frequency drops in the grid. More of the recently build wind turbines use variable speed generators. Unlike fixed speed generators, these generators do not naturally contribute to the recovery of the frequency drop since the rotor rpm is decoupled from the grid frequency. This decoupling is achieved by controller and power conditioning units. The studies reviewed in this paper focused on the design of such a controller so that the wind turbine could react to frequency drops. Another approach to responding to frequency drops is to connect an energy storage system to the DC bus of variable speed generator. Flywheels have been used as energy storage systems to fill energy gaps in several applications and can be used for frequency recovery application for wind turbines as well. The objective of this study was to demonstrate the improvement of frequency stability of wind turbines connected to electrical grids in the presence of flywheel energy storage systems (FESS). Studies reviewed show that FESS can enhance the power quality and frequency stability of wind turbines connected to an electrical grid.


Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4391
Author(s):  
Mariano G. Ippolito ◽  
Fabio Massaro ◽  
Rossano Musca ◽  
Gaetano Zizzo

This work examines the operation of the autonomous power system of a geographical island assuming the integration of significant generation shares from renewable energy sources and the installation of the required storage systems. The frequency stability of the system is investigated considering different operating conditions, in terms of load demand and renewable power generation. The main focus of the work is an original control strategy specifically designed for power converters interfacing storage units to the grid. The proposed strategy is based on an extended frequency droop control, which selects specific droop settings depending on the operating mode—charge or discharge—of the storage unit. A simulation model of the whole electrical system is developed for dynamic analysis. The model also implements the possibility of including specific auxiliary frequency controls for synthetic inertia and primary reserve. The results of the simulation and analysis indicate that the proposed control strategy has a significant positive effect, making the storage units able to provide a fundamental and more effective support to the frequency stability of the system. The application of the proposed control strategy to storage units also reduces the need for a contribution to the frequency control from intermittent and variable sources, making the whole system more robust, stable and reliable.


2021 ◽  
Vol 7 ◽  
pp. 6148-6161
Author(s):  
Gefen Ben Yosef ◽  
Aviad Navon ◽  
Olga Poliak ◽  
Naomi Etzion ◽  
Nurit Gal ◽  
...  

2021 ◽  
Vol 9 ◽  
Author(s):  
Qing Chen ◽  
Rui Xie ◽  
Yuyan Chen ◽  
Heyu Liu ◽  
Shengqi Zhang ◽  
...  

With the increase of the renewable energy penetration (REP) level in the interconnected power grid, the proportion of the grid-connected conventional synchronous generators reduces continuously, resulting in the decrease of the system inertia. The insufficient system inertia brings challenges to the system frequency stability. Battery energy storage systems (BESSs), regarded as the high-quality frequency regulation resource, play an important role in maintaining the frequency stability of the system with the high REP level. To configure the proper power of BESSs in system frequency regulation, a BESS power configuration scheme (PCS) considering the REP constraint is proposed in this paper. In particular, the process to obtain the REP boundary of the interconnected grid on the premise of system frequency stability is included in the PCS, and the optimal power configuration of the BESS is further determined on the analysis of the BESS impact on the REP boundary. Furthermore, a simulation model of the Australian five-area interconnected power grid is built in MATLAB/Simulink, and the proposed REP-constrained PCS is verified and analyzed. At last, the promising results show that the PCS can take full advantages of the BESS in frequency regulation and meet the system requirement of the frequency stability at a particular REP level.


Author(s):  
T. A. Dodson ◽  
E. Völkl ◽  
L. F. Allard ◽  
T. A. Nolan

The process of moving to a fully digital microscopy laboratory requires changes in instrumentation, computing hardware, computing software, data storage systems, and data networks, as well as in the operating procedures of each facility. Moving from analog to digital systems in the microscopy laboratory is similar to the instrumentation projects being undertaken in many scientific labs. A central problem of any of these projects is to create the best combination of hardware and software to effectively control the parameters of data collection and then to actually acquire data from the instrument. This problem is particularly acute for the microscopist who wishes to "digitize" the operation of a transmission or scanning electron microscope. Although the basic physics of each type of instrument and the type of data (images & spectra) generated by each are very similar, each manufacturer approaches automation differently. The communications interfaces vary as well as the command language used to control the instrument.


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