Increasing the Utilization of Existing Infrastructures by Using the Newly Introduced Boundary Voltage Limits

Abstract

The increasing share of distributed generation aggravates voltage limit compliance at customers’ delivery points. Currently, grid operators validate compliance with the voltage limits specified in Grid Codes by conducting load flow simulations at the medium voltage level, considering the connected low voltage grids as ‘loads’ to reduce the modeling effort. This approach does not support the accurate validation of limit compliance, as the voltage drops at the low voltage level are unknown. Nevertheless, to guarantee acceptable voltages even under worst-case conditions, safety margins are involved that impair the utilization of the electricity infrastructure. This study conducts load flows simulations in a test distribution grid, revealing the variable character of the voltage limits at different system boundaries. The conventional load model is extended by new parameters—the boundary voltage limits—to enable the consideration of variable voltage limits in load flow analysis of LINK-based smart grids. The standardized structure of the LINK-architecture allows for the systematic and accurate validation of voltage limit compliance by reducing the required modeling data to the technically necessary minimum. Use cases are specified that allows smart grids to increase the utilization of the electricity infrastructure by day-ahead scheduling and short-term adaptation of boundary voltage limits.

Effect of Individual Volt/var Control Strategies in LINK-Based Smart Grids with a High Photovoltaic Share

“…The LINK-based chain modeling procedure, introduced in [35] and overviewed in Figure 2, is used to calculate the test grids' behavior for different Volt/var control arrangements. In contrast with conventional load modeling, this approach uses the BVL-concept to validate voltage limit compliance throughout the entire Smart Grid through separate analysis of each system level.…”

“…Numerous studies have been conducted to analyze the effects of different Volt/var control strategies on the behavior of LV grids using load flow simulations [13,[31][32][33][34]. These studies calculate the grid state for a specified voltage at the slack node, but do not analyze the impact of Volt/var control on the boundary voltage limits (BVL) at the distribution and supplying substation levels [35] for different local control strategies such as cosϕ(P), Q(U), and OLTC in distribution transformers. This paper upgrades the L(U) local control strategy to X(U), supporting the increase in electricity demand, e.g., due to e-mobility.…”