Dynamics and operation of renewable-based power systems

The accurate identification of fault contribution is crucial to proper operation of protection systems. Considering the case in Figure 3, Relay 2 (R2) experiences a large amount of fault current flowing through it. However, the proper implementation of selectivity requires that Relay 8 (R8) picks up and isolates the fault not Relay 2. There are several communication-based protection solutions proposed in the literature to counter these problems]. However, for proper operation of such systems, thorough understanding of inverter’s fault behavior is key. Only in that fashion is it possible to anticipate different fault conditions and program protection devices.In addition to these challenges, SIs are highly dynamic devices that interact with the grid and try to influence its operation. They are able to operate in a series of modes which change SI’s output with respect to local voltage and/or frequency. This makes them more unpredictable. Therefore, there is an imminent need to investigvior of Sis.

Plan :uses smat grid In a conventional power system, electricity is distributed from the power plants through the transmission and distribution networks to final consumers. Transmission and distribution networks are designed to deliver the electricity at the consumer side at a predefined voltage level. Photovoltaic power generation is in general connected at the distribution level of the power system. For this reason, it is possible for the power produced by the PV to cause a 'counter' power flow from the consumer side to be delivered to other consumers through the distribution network. This phenomenon may present two challenges: an increase of the voltage in areas with high PV production; and voltage fluctuation throughout the system due to the intermittency Low frequency Oscillations.Unstable lowfrequency oscillations in power systems with CIGs can appear due to a variety of forms of interaction between the controllers of the converters and other system components. The outer (power and voltage) control loops and the PLL of CIGs can, for instance, lead to unstable low frequency oscil- lations [73]. System strength at the connection point of CIGs has a significant influence on the stability of low-frequency oscillations , where the interaction between direct-drive permanent-magnet generator (PMG) wind turbines and weak AC grids has resulted in the system experiencing sustained os- cillations since 2014. The oscillation frequencies range between 20 Hz and 40 Hz, depending on the system operating conditions In power systems with low short circuit ratios (SCR), i.e., weak grids with SCR less than 2 the oscillations may become unstable and could lead to growing low-frequency oscillations in the PMG and the local grid.