Photovoltaic Inverter Profiles in Relation to the European Network Code NC RfG and the Requirements of Polish Distribution System Operators

Abstract

The presently observed rapid increase in photovoltaic (PV) micro-installation connections to low-voltage networks, resulting from numerous financial support programmes, European Union (EU) energy policy and growing social awareness of environmental and economic issues, raise the question if PV inverters widely available in EU market fulfil the numerous technical requirements specified in European and Polish regulations. The paper presents the results of an experimental study carried out on three PV Inverters widely available in the EU in accordance with the EU network code NC RfG, standard EN 50549-1:2019 and internal Polish distribution system operators’ (DSOs’) regulations, governing PV inverter cooperation with the low-voltage distribution network. The laboratory test stand scheme and its description are presented. In each test, at least one of the inverters encountered issues, either with the operation in required frequency ranges (one PV inverter), activating reactive power control modes (all three PV inverters), maintaining required power generation gradient after tripping (one PV inverter) or under-voltage ride through immunity (one PV inverter). The obtained results have shown that all tested PV inverters did not meet requirements that are the key to maintaining reliable and safe operation of transmission and distribution electrical networks.

A Real-Time Energy Management System Design for a Developed PV-Based Distributed Generator Considering the Grid Code Requirements in Turkey

“…Islanding detection methods (IDMs) can be classified into remote, local, and intelligent methods [2,3]. The conventional IDMs are defined as passive, active, and hybrid methods.…”

“…(2) The total capacity of the power generation plants connected to the distribution system with the LV level must not exceed 30% of the connected distribution transformer power. (3) The stiffness ratio is defined as the rate of the short circuit current of the distribution system/the nominal current of the distribution network. It must be over 30 for the co-generation plants that the installed power is over 1 MWp, and it must be over 70 for other power generation plants [41,42].…”

“…Many countries have established some electrical criteria, taking into consideration the requirements and infrastructure of the national grid called "Grid Code" within this scope [1,2]. While a DG system provides the conditions for connecting to the grid, the necessary monitoring and protection equipment must be present at the grid side [3,4]. For this reason, the DG system must be installed in such a way that it can take the protection…”

“…This w age the DG system components, render the system inoperable (blackout), and e the life safety of the operator if an operator is working in the DG system. For thi when an undesired islanding event of DG systems occurs, the DG system must di from the mains as soon as determined by the standards [1][2][3]. There are many studies in the literature on the connection of DGs to the grid studies, some general approaches related to connection criteria were presented, o ficiency of the system was investigated with the help of some simulation program study, electrical connections have put forward the DG system in Turkey that is for connection to the network in real-time and, following the country's Grid C been proposed a system protection and monitoring system.…”

“…This will damage the DG system components, render the system inoperable (blackout), and endanger the life safety of the operator if an operator is working in the DG system. For this reason, when an undesired islanding event of DG systems occurs, the DG system must disconnect from the mains as soon as determined by the standards [1][2][3].…”