Effects of Energy Storage Systems Grid Code Requirements on Interface Protection Performances in Low Voltage Networks

Abstract

Abstract:The ever-growing penetration of local generation in distribution networks and the large diffusion of energy storage systems (ESSs) foreseen in the near future are bound to affect the effectiveness of interface protection systems (IPSs), with negative impact on the safety of medium voltage (MV) and low voltage (LV) systems. With the scope of preserving the main network stability, international and national grid connection codes have been updated recently. Consequently, distributed generators (DGs) and storage units are increasingly called to provide stabilizing functions according to local voltage and frequency. This can be achieved by suitably controlling the electronic power converters interfacing small-scale generators and storage units to the network. The paper focuses on the regulating functions required to storage units by grid codes currently in force in the European area. Indeed, even if such regulating actions would enable local units in participating to network stability under normal steady-state operating conditions, it is shown through dynamic simulations that they may increase the risk of unintentional islanding occurrence. This means that dangerous operating conditions may arise in LV networks in case dispersed generators and storage systems are present, even if all the end-users are compliant with currently applied connection standards.

Evaluation of the Use of Class B LoRaWAN for the Coordination of Distributed Interface Protection Systems in Smart Grids

“…IPSs are designed to detect the loss of connection with the DN and to disconnect the supervised generation units, in order to inhibit their operation in islanded mode. The loss of the main connection is usually detected as a violation of predefined voltage and frequency acceptable bands [10]. The safe implementation of anti-islanding protection functions represents a critical task in modern DNs, due to the relevant risks related to the unintentional islanding of DG units, even if operated for a very short time.…”

“…Although the anti-islanding mechanisms defined by current regulatory frameworks proved to be effective in most cases, recent studies demonstrated that, under the different stabilizing functions required by national and international grid codes, the measurement techniques implemented in current IPSs could be inadequate [9]. Anti-islanding protection functions could in fact fail, particularly during transients, due to the masking effect of stabilizing functions on IPSs [10]. To cope with this issue, different anti-islanding mechanisms have been recently proposed by the literature, from advanced measurement techniques, to the application of active mechanisms.…”

“…A passive islanding protection method, for instance, was presented in [11], while the adoption of the traveling wave analysis was proposed in [12]. Active mechanisms have been also taken into consideration, such as the observation of the network equivalent impedance through a high frequency measure based on an intentional current injection, and the provisioning of remote signals by Distribution System Operators (DSOs) [10].…”

Proposals for Enhancing Frequency Control in Weak and Isolated Power Systems: Application to the Wind-Diesel Power System of San Cristobal Island-Ecuador

“…Since these strategies force the wind turbine to operate under non-optimal conditions, the cost of the wind energy waste could represent a clear disadvantage. However, many grid codes consider the possibility of sacrificing part of the generated energy in order to safeguard the quality, stability, reliability and continuity of the power supply [17,18]. This paper presents some proposals aimed at enhancing the frequency response of a weak and isolated power system with a significant share of wind energy by using the approach offered by the second group of solutions, that is, by leveraging the existing equipment installed in the system.…”

Review of Voltage and Frequency Grid Code Specifications for Electrical Energy Storage Applications

“…Bignucolo et al [59] focused on the regulating functions required to storage units by Grid Codes to the low-voltage networks in the European area. The study shows that the dangerous operating conditions may arise in low-voltage networks when dispersed generators and storage systems are present.…”