Fuzzy Logic Controller-based Synchronverter in Grid-connected Solar Power System with Adaptive Damping Factor*

 Abstract

In the last few years, the development of solar power systems has been rapid due to their technological maturity and cost-effectiveness. However, integrating solar power into the grid can negatively impact frequency stability, as the lack of rotating masses and inertial response can destabilize the power grid. To address this issue, a synchronverter, an inverter that mimics the operation of a synchronous generator, is crucial. It stabilizes the power grid by emulating a virtual inertia. However, a conventional proportional-integral (PI)-based synchronverter lacks an adaptive damping factor (Dp) or a digitalized smart controller to manage fast-responding solar inputs. Therefore, a novel fuzzy logic controller (FLC) framework is proposed to operate the synchronverter in a grid-connected solar power system. The FLC controls Dp in real-time, achieving a balance between speed and stability for frequency error correction based on frequency difference. The results of four case studies performed in Matlab/Simulink demonstrate that the proposed FLC-based synchronverter can stabilize the grid frequency, reducing the frequency deviation by at least 0.2 Hz (0.4%) compared to the conventional PI-based synchronverter.

Keywords

Fuzzy logic controller (FLC), synchronverter, renewable energy system (RES), grid stability, solar power system

BLOCK DIAGRAM:

                                                           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

CONCLUSION:

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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