Cost study of DER flexibility installation and distribution system reinforcement to mitigate grid congestion

(DER) has been increasing globally. The increasing PV connection has raised concerns about grid congestion in the distribution networks due to the growing reverse power flow from PV.

Conventionally, measures have primarily focused on grid reinforcement; however, the high costs and prolonged new construction periods have become significant issues. In recent years, many initiatives have been reported to avoid or defer grid upgrade by utilizing DER flexibility.

In such situations, comparing the costs of grid reinforcement versus the introduction of DER flexibility will be an important metric in determining the optimal congestion mitigation strategy.

In this study, case studies were conducted to compare the costs of grid reinforcement with the introduction of DER flexibility as measures against grid congestion from large-scale PV deployment. Specifically, three grid reinforcement cases were set up and the required capacity of the installed BESS was assumed for each case. It was found that the introduction of BESS can be cost-effective in cases requiring large-scale grid reinforcement to accommodate the connection of megawatt-scale PV, particularly when the construction of long-length distribution lines is necessary.

Next, Monte Carlo simulations were conducted using weather-dependent PV generation as a variable to enable a cost comparison as an analysis considering uncertainties. The results showed that, for 500-kW PV installation, BESS deployment can become cost-advantageous against large-scale grid upgrades. In particular, greater cost advantages are expected when the

BESS capacity is sized based on average PV generation rather than sizing to accommodate generation up to the 90th percentile.

Thus, the cost calculations based on practical case studies and the statistical analysis considering uncertainties in this study can serve as valuable guidance in this regard.