Photovoltaic Hosting Capacity of Distribution Networks

Abstract

Due to an increasing share of renewable energy sources and widespread adoption of distributed photovoltaics (PV), the ability of the distribution networks to reliably interconnect new PV installations without hindering the power system's operation gained a lot of interest in the recent decade. Political support and falling prices of the photovoltaics make the panels available for as small as single household installations and some of the network operators have already reported the power quality issues caused by the PVs. To address this issue, this thesis investigates the PV hosting capacity (HC) of low-voltage distribution networks. The thesis is split into two main contributions centered around the power quality limitations of the HC and network structure influence on the HC. The thesis starts with a review of the HC definitions, its most common limiting factors, and reports on the results of a measurement campaign of low-voltage substations. In the first part, a Monte Carlo-based HC evaluation methodology is presented, which is used for the PV-only and energy storage-augmented scenarios. Alongside the single-phase PV installations, a voltage unbalance (VU) mitigation methodology is presented. Despite the VU being a very strict limit, it can be mitigated by relatively low power injections. Moreover, a comparison of PV curtailment and network reinforcement is presented to find the break-even points of the costs of the two. The second part of the thesis presents the distribution network's structure impact on the hosting capacity. A fixed set of customers is simulated with multiple feeding substations and a varying number of PV plants. The slime mold algorithm was proposed to be employed for generating numerous network topologies and its advantages over other algorithms were shown. The results revealed that around one-third of the customers can have PV installations until the HC is depleted. Voltage control can increase the HC, however remains the risk of possible need to change residential PV policies to sustain the current pace of PV installations. Finally, the thesis explores the practical side of the HC and analyzes the accuracy of distribution network state estimation. A PV safety margin is proposed, that represents an equivalent PV power that has to be curtailed in order to keep the estimated values below the actual values of the states.