In recent years, renewable energy sources, specifically solar power systems, have developed rapidly owing to their technological maturity and cost effectiveness. However, its grid integration deteriorates frequency stability because of insufficient rotating masses and inertial response. Hence, a synchronverter, which is an inverter that mimics the operation of a synchronous generator, is crucial to interface solar power in a power grid. It stabilizes the power grid by emulating a virtual inertia. However, a conventional proportional-integral (PI)-based synchronverter is not equipped with an adaptive damping factor (Dp) or a digitalized smart controller to manage fast-responding solar inputs. Hence, a novel fuzzy logic controller (FLC) framework is proposed such that the synchronverter can operate in a grid-connected solar power system. In this study, Dp is controlled in real time using an FLC to achieve balance between speed and stability for frequency error correction based on frequency difference. Results of four case studies performed in Matlab/Simulink show that the proposed FLC-based synchronverter can stabilize the grid frequency by reducing the frequency deviation by at least 0.2 Hz (0.4%), as compared with the conventional PI-based synchronverter.
- Fuzzy logic controller (FLC)
- Renewable energy system (RES)
- Grid stability
- Solar power system
Fig. 1 Power section of synchronverter
EXPECTED SIMULATION RESULTS:
Fig. 2 Active power for varying resistive loads (RL)
Fig. 3 Outputs of synchronverter for first case study
Fig. 4 Testing environment for second case study
Fig. 5 Outputs of synchronverter for second case study
Fig. 6 Testing environment for third case study
Fig. 7 Outputs of synchronverter for third case study
Fig. 8 Testing environment for fourth case study
Fig. 9 Outputs of synchronverter for fourth case study
Herein, a novel FLC-based framework was proposed to control a synchronverter in a grid- connected solar power system under dynamic weather conditions. Four case studies were simulated in Matlab/Simulink, and the results validated the ability of the proposed controller in stabilizing fg by reducing the frequency deviation by at least 0.2 Hz (0.4%), as compared with the conventional PI-based synchronverter. The performance of the FLC-based synchronverter was optimal even under sudden load changes or varying irradiances and temperatures. P was injected or absorbed whenever the frequency decreased or increased, respectively. The Dp controlled by the FLC was able to balance between transient speed and stability, whereby a larger Dp afforded a more prominent dampening effect, and vice versa.
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