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Electrical and Computer Engineering | Engineering
Securing a future sustainable decarbonised economy involves moving towards a system with rising penetration levels of distributed photovoltaics (PVs) within the low voltage distribution network (LVDN). This power system evolution is displacing conventional generators and has resulted in a decline in inertia that is essential for frequency stability. Emerging network codes require PV generators to maintain a scheduled curtailed active power (CAP) reserve for under-frequency contingencies. In this paper, the development, verification and application of an enhanced, two-stage grid-connected, state-space, linear parameter varying (LPV) PV system model is presented. The LPV model provides accurate and efficient modelling for PV systems over the wide range of operating points associated with curtailed active power and is suitable for power systems with large numbers of distributed PV systems capable of frequency support in the LVDN, to be simulated within reasonable simulation times. In addition, the LPV model can be used to investigate voltage rise due to reverse active power. The model performance is evaluated using recorded experimental data with step changes in irradiation and active power curtailment. The measured data is generated from a power hardware in the loop (PHIL) testbed. The model’s performance is investigated on an adapted radial European LVDN benchmark with several distributed PV systems to present some of the challenges, opportunities and benefits. Step changes in solar irradiation are used to evaluate the dynamic behaviour of the LPV model compared to a discrete-time electromagnetic transient (EMT) model. A frequency droop control characteristic for frequency support is demonstrated. The results show a computational burden reduction of 132:1 compared to the EMT model and demonstrate the voltage rise due to reverse active power from providing frequency support during under-frequency contingencies.
Levis C, O’Loughlin C, O’Donnell T, Hill M. An Enhanced Two-Stage Grid-Connected Linear Parameter Varying Photovoltaic System Model for Frequency Support Strategy Evaluation. Energies. 2019; 12(24):4739. https://doi.org/10.3390/en12244739