Defining Customer Export Limits in PV-Rich Low Voltage Networks

Abstract

The growing adoption of residential photovoltaic (PV) systems around the world is presenting distribution network operators (DNOs) with technical challenges, particularly on low voltage (LV) networks. The need to mitigate these issues with simple yet effective measures in countries with high PV penetrations is likely to drive the adoption of limits on the very exports that affect this infrastructure. Defining the most adequate limit, however, requires understanding the tradeoffs between the technical benefits and the effects on PV owners. This paper proposes two methodologies: an optimal power flow (OPF) based technique to define the export limit that solves technical problems with minimal curtailment, and a Monte Carlo based analysis to investigate the spectrum of such tradeoffs considering different PV penetrations and export limits. A real U.K. residential LV network with 180 customers is analyzed using realistic 1-min resolution daily load and PV generation profiles across seasons. Results demonstrate that, for DNOs, the OPFbased approach is effective in determining the most technically adequate export limit. However, for policy makers, the spectrum of tradeoffs provided by the Monte Carlo approach can help defining export limits that reduce curtailment at the expense of partially mitigating technical issues. Index Terms-Low voltage networks, optimal power flow, photovoltaics, PV management. I. INTRODUCTION T HE need to reduce CO 2 emissions combined with attractive incentive mechanisms such as feed-in tariffs (FIT) or net metering schemes have encouraged in the last few years the growth of the global photovoltaic (PV) generation capacity,

Hierarchical coordination strategy for three‐phase MV and LV distribution networks with high‐penetration residential PV units

“…This paper adopts the method ‘export limits’ in [30] to mitigate overvoltage issues in the LV level. This method is simpler than general voltage control strategies (e.g.…”

“…Additionally, this method defines the export limits at each node to bind the voltage variations below the upper limit. The calculations of export limits have already been discussed in detail in [30] by Monte Carlo simulations or multi‐scenario optimisations. Each node needs to check whether its net active power and reactive power satisfy export limits.…”

Optimal Coordination of PV Active Power Curtailment and EVs Charging among Aggregators

“…In this stage, the DSO seeks to coordinate for each aggregator, its maximum PV generation and the charging power of all their EVs to maximise the operational performance of the network and fulfill the energy and power needs of the end users. Since the total PV power managed by an aggregator k could overload the DSO's assets due to the reverse power flow, it has to be limited to a certain power level, i.e., it should be applied an active power curtailment strategy (e.g., fixing a maximum point to active power [12][13][14][15] or considering a reference signal as the voltage at the connection node [16,17]) for the PV units under that aggregator. Both the export limit of PV power and the charging profile for each aggregator are centrally calculated based on a linear optimisation model which takes as inputs the requirements of each aggregator, its forecasted load profile and the thermal limits of the network's assets.…”

“…On the other hand, in [12], an optimal power flow (OPF) problem based on a quadratic programming formulation is proposed to minimise the energy curtailment of medium-scale PV units by finding an optimal power limit to guarantee the network will operate without thermal or voltage problems. A similar criterion for PV power curtailment in LV networks was employed in [13]. The authors extended the OPF formulation in [12] to the unbalanced three-phase case.…”

Solar irradiance estimations for modeling the variability of photovoltaic generation and assessing violations of grid constraints: A comparison between satellite and pyranometers measurements with load flow simulations

“…Distribution system operators (DSOs) typically use model-based estimates of PV generation for feasibility studies when connecting new PV power plants to verify that the grid can withstand the power injections without determining violations of statutory voltage limits and cables' ampacities (see e.g. 1 ). Irradiance forecasts might be relevant for DSOs to schedule the operation of utility-scale storage facilities to mitigate the impact of PV generation on their grids, or if specific grid codes (see, e.g., the notion of balance group in the Swiss grid code 2 ) to improve the forecast of their aggregated demand when they are penalized for incurring in unbalances.…”