Analysis of the Impact of Microgrid Penetration on Power System Dynamics

Abstract

The paper proposes a stochastic model to analyse the dynamic coupling of the transmission system, the electricity market and microgrids. The focus is on the impact of microgrids on the transient response of the system and, in particular, on frequency variations. Extensive Monte Carlo simulations are performed on the IEEE 39-bus system, and show that the dynamic response of the transmission system is affected in a non trivial way by both the number and the size of the microgrids

Stochastic Frequency Control of Grid-Connected Microgrids

“…The decisions of the EMS of the MGs are thus driven by the price of electricity and there is the need to properly account for the market behavior. As thoroughly discussed in [14] and [15], in fact, the market plays a prominent role in the dynamic response of the interconnected MGs. Hence, in the case study, the electricity market is modeled as in [14].…”

“…COI implicitly takes into account the effect of machine regulation as well as of network losses. The interested reader can find more details on this model and its notation in [14].…”

“…Finally, the reference set point of the active power p ref , is defined by the EMS of the MG and it is imposed by the slack variable p st , as shown in Figure 1. The interested reader can find a detailed discussion on the model of the MG in [14].…”

“…Extensive realistic simulation in [14] showed that MGs that only focus on their own individual convenience, e.g., the maximization of individual revenues, may lead the frequency of the grid out of a safety range. Accordingly, in this paper we propose a strategy that mitigates the impact of MGs on the power grid while at the same time allows the MGs to continue to operate advantageously according to their own policy.…”

“…This is mainly due to the difficulty of modeling such a large-scale and highgranularity power system with the required level of accuracy. In this context, realistic simulations performed in [14] and [15] showed that a large number of MGs that opportunistically manage their power flow to optimize some individual internal utility function (e.g., revenues in selling energies) may cause large frequency deviations of the interconnecting transmission system, eventually endangering the stability of the grid as a whole. Conclusions drawn in [14] and [15] suggest the need to design appropriate control methods to maintain the power grid within safe operational boundaries as the number of MGs increases.…”