Abstract
This paper demonstrates the use of a novel virtual synchronous generator (VSG) to provide dynamic frequency support in an autonomous photovoltaic (PV)–diesel hybrid microgrid with an energy storage system (ESS). Due to the lack of enough rotating machines, PV fluctuation might give rise to unacceptable frequency excursions in the microgrid. The VSG entails controlling the voltage-source inverter (VSI) to emulate a virtual inertial and a virtual damping via power injection from/to the ESS. The effect of the VSG on the frequency is investigated. The virtual inertia decreases the maximum frequency deviation (MFD) and the rate of change of frequency (RoCoF), but in exchange for raising the virtual inertia, the system is more oscillating. Meanwhile, raising the virtual damping brings reductions in the amplitude of the oscillations of frequency. However, the dynamic frequency support provided by them is lagging behind. In this regard, an improved VSG based on the differential feedforward of the diesel generator set (DGS) output current is proposed to further mitigate the MFD and the RoCoF. Simulations and experimental results from an autonomous microgrid consisted of a 400 kW DGS, and a 100 kVA VSG are provided to validate the discussion.
Highlights
Photovoltaic (PV)–diesel hybrid microgrids are a fine choice for electricity generation in isolated regions where PV resource is rich [1]
It can be found that the virtual inertia control is more efficient in reducing the rate of change of frequency (RoCoF) than the other control methods, but it uses more energy in reducing the maximum frequency deviation (MFD)
The dynamic frequency support control for the autonomous PV–diesel hybrid microgrids with the energy storage system (ESS) based on virtual synchronous generator (VSG) is investigated in this paper
Summary
Photovoltaic (PV)–diesel hybrid microgrids are a fine choice for electricity generation in isolated regions where PV resource is rich [1]. An ESS-based dynamic frequency support solution is used to cope with system frequency deviation by filtering of the output power of stochastic resources [5]. This strategy needs the measurement of the output power, which requires a communication bus. The droop method is used to control the distributed energy storage interfaces independently by the local measurements, without a communication bus [6,7,8,9,10] This strategy is aimed to provide only frequency adjustment by employing the permanent frequency droop form, it cannot deal with the problem of dynamic frequency regulation. In virtual synchronous generator (VSG) method, which is VSI based, the ESS
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