Monotonicity Criterion-Based Power Quality Improvement in Distributed Energy Systems with Solar PV Integration

This study investigates power quality improvement in a distributed energy system with a solar PV system, based on the monotonicity criterion. The research considered a range of IEEE bus systems—namely, the IEEE 14-bus, IEEE 33-bus, IEEE 57-bus, and IEEE 118-bus systems—integrated with PV modules. Initially, load profile curves for various buses were analyzed to identify power quality issues within the system. Key parameters such as node-wise voltage profile, voltage unbalance, harmonic distortion, power factor, dominant harmonic order, frequency variation, and power quality index were formulated from the simulations. The study explores potential optimizations in the power system, focusing on varying the maximum bus voltage between 5% and 15%, in conjunction with angle variations from 1 to 5 degrees. The monotonicity criterion was applied to select optimal PV distribution, aimed at compensating for load variation and improving power quality. Compensation levels ranged from 5% to 100%, targeting real and reactive power matching through harmonic injection up to the 497th order. The simulation results confirm that the proposed scheme effectively balances frequency variation within a 1 to 2 Hz range and maintains a consistent voltage profile across the distribution system. Additionally, the balance in the number of PV modules, regardless of voltage levels, demonstrates the superiority of the proposed method. The study highlights the potential for advanced power electronics converters, high-frequency switching devices, active harmonic filters, grid-connected energy storage systems, and sophisticated control algorithms to achieve near-perfect power matching, even up to the 497th harmonic, despite non-linearities in network behavior and PV performance.