BELECTRIC Coevordenkanaal PV
The brief
The soon-to-be-commissioned PV plant will consist of 46 solar panels connected to the grid via four inverters. These inverters convert the DC (direct current) power generated by the PV panels into AC (active current) power and are controlled by a master controller known as the Power Park Controller (PPC). The PPC sends command signals to the inverters in order to control the PV plant's active and reactive power outputs in accordance with grid requirements.
Challenge
We were tasked with investigating the plant's grid compliance requirements as outlined in the EU code in the Netherlands (Netcode elektriciteit). Grid codes in the EU differ slightly from those in the UK. For example, the power distribution network in the United Kingdom is connected to an 11 kV switchboard, whereas the switchboard in the Netherlands is 10.5 kV.
There were also differences in the standards for each of the simulation studies we conducted, so we had to ensure that we understood the fine lines between EU and UK regulations and then modify our studies accordingly.
Solution
We received general plant data, single line diagrams (SLDs), and datasheets for transformers, cables, and inverters from BELECTRIC. They also provided us with the inverter's dynamic model, which is critical for RMS calculations. We built the plant model in our simulation software using the available data and conducted four different simulation studies to ensure the plant's grid compliance:
Reactive power capability Assessment:
The requirements for reactive power capability of the plant are outlined in the “RfG Compliance Verification” document issued by Netbeheer Nederland. Every generating plant has the ability to provide certain reactive power if there is a requirement in the network. We conducted several load flow studies to determine the plant's compliance with the applicable reactive power requirements.
Fault infeed studies:
When a fault occurs in an electrical network, such as a short-circuit fault, the voltage at the point of the fault drops dramatically. This causes high currents to flow from across the network to the fault location. This study evaluates the PV farm's short-circuit contribution in the event of symmetrical and asymmetrical faults in the distribution network.
Voltage fluctuations Assessment:
The IEC 61000-3-7 standard and the Netcode elektriciteit recommend flicker and voltage fluctuation limits for new connections that should not be exceeded. In this study, we investigated three types of disturbances: Rapid voltage change (RVC) caused by transformer magnetising inrush currents, RVC caused by a sudden loss of generation (voltage step change), and flicker effect due to continuous operation.
Harmonic Distortion Assessment:
Since the site was connected to the Distribution system operator (DSO) at 10.5 kV, the harmonic voltage distortions were compared against the limits defined in IEC 61000-3-6 for connections at medium voltage. The total current and voltage harmonic distortion, as well as all harmonic levels from the 2nd to the 50th order, are found to be within the planning levels in this study.
Based on the results of these simulation studies, we were able to confirm that this PV plant would meet all of the requirements specified in the EU grid code.