P-HiL Evaluation of Virtual Inertia Support to the Nordic Power System by an HVDC Terminal

Abstract

This paper provides an assessment of the effect from virtual inertia provided by an HVDC converter terminal on the Nordic power system. The analysis is based on results from Power-Hardware-in-the-Loop (P-HiL) tests with a laboratory-scale Modular Multilevel Converter (MMC) representing an HVDC terminal interfaced with a real-time phasor simulation of the Nordic grid. The applied control method for providing virtual inertia is utilizing the derivative of the locally measured grid frequency to adapt the power reference for the studied converter terminal. The power injection provided by the converter and the resulting impact on the frequency dynamics of the power system are investigated as a function of the emulated inertia constant and the frequency droop gain. The results demonstrate how the HVDC converter can effectively support the dynamic response of the power system when exposed to large load transients by improving the frequency nadir and reducing the Rate-of-Change-of-Frequency (ROCOF).

Economic value of inertia support from HVDC system

“…It is pertinent to mention here that the value of the HVDC system inertia constant (H vsm ) depends on the additional power injection capability of the HVDC system, i.e. available capacity [10,11]. For the considered scenario, the power flow on the HVDC link is on its rated value.…”

“…The power flow is divided by the number of poles based on a single line representation in [15] for the DC branches. The active power flow on a DC branch d between the DC nodes e and f is bound by the rated limits as given in (11). The DC branches are considered lossless as per (12).…”

“…1. The two AC systems are represented by their Thevenin equivalent with the total generation and total load data based on [11]. The AC system-1 and AC system-2 in Fig.…”

“…The authors in [10] have presented the dynamic analysis for a Modular Multilevel Converter (MMC) based HVDC links to provide inertia support. The analysis for virtual inertia support for the NSA by an HVDC Terminal has been presented in [11].…”