Comparison of Field Measurements and EMT Simulation Results on a Multi-Level STATCOM for Grid Integration of London Array Wind Farm

Simulation results are widely used in the design of electrical systems such as offshore wind power plants (OWPPs) and for determination of grid compliance. Measurements constitute an important part in the evaluation process of the OWPP, including passive and active components such as the static compensator (STATCOM). Quality measurement data allow the system designer to obtain real-life knowledge on the operating characteristics of the electrical component(s) for various operating scenarios of both the OWPP and the external grid. Furthermore, measurement data constitute an indispensable part of the evaluation of the simulation models of the OWPP components.
The purpose of this paper is to develop and validate an electromagnetic transient (EMT) generic model of the modular multi-level cascaded converter (MMCC) STATCOM based on comparison with field measurements. For this purpose, measurement data have been acquired on a commercial ±50 MVAr state-of-the-art (SOA) MMCC STATCOM. The STATCOM is located at the point of common connection (PCC) at the world’s largest OWPP, London Array (LAOWPP). According to the authors’ knowledge, the presented paper will be the first of its kind to compare a detailed model of the STATCOM with actual field measurements for a commercial MMCC STATCOM.
Furthermore, the paper offers the reader, being a researcher, transmission system operator, converter designer or a WPP developer etc., the unique opportunity to gain in-depth knowledge of the operating characteristics of the STATCOM for wind power integration, as well as of the validity of applying a generic model of the STATCOM without knowledge of the actual implemented control system.
The proposed model is integrated into an aggregated EMT model of LAOWPP, which will be used to investigate possible resonance phenomena that will be shown in the paper to affect the harmonic distortion level. The STATCOM distortion level will be shown to be highly affected by the number of wind turbine generators (WTGs) in service. It will be shown that the inclusion of band rejection filters (BRFs) in the WTGs’ control loop lowers the STATCOM distortion level. It is found that the total inter-harmonic distortion (TIHD) index calculated according to IEC Standard 61000-4-7 is useful for assessing possible and undesired control interaction between the power electronic devices (PEDs) in OWPPs. The total harmonic distortion (THD) index, on the other hand, is found to contain very little information on possible PED controller interaction.