Photovoltaic Grid-Connected System Model

The photovoltaic grid-connected system model represents a critical research direction in power electronics and renewable energy, commonly employed in graduation projects and engineering applications. The core of this system model lies in simulating photovoltaic array generation characteristics and achieving stable grid integration through inverters.

Typical model construction generally includes the following modules: Photovoltaic Array Model - Based on the single-diode equivalent circuit, considering the impact of solar irradiance and ambient temperature on output characteristics. Implementation typically involves solving the I-V characteristic equation numerically, with parameters like photocurrent and diode saturation current calculated from environmental conditions. MPPT Control - Utilizes perturbation and observation (P&O) or incremental conductance algorithms for maximum power point tracking. The P&O method periodically perturbs the operating voltage and observes power changes, while the incremental conductance method compares the instantaneous conductance to the incremental conductance for faster tracking. DC/AC Inversion - Generates grid-compliant AC power through SPWM (Sinusoidal Pulse Width Modulation) or SVPWM (Space Vector PWM) techniques. SVPWM implementation involves sector identification, voltage vector time calculation, and switching sequence generation for improved DC bus utilization. Phase-Locked Loop Synchronization - Ensures inverter output voltage synchronization with grid phase. Typically implemented using software-based PLL algorithms that track grid frequency and phase angle through feedback control loops. Protection Circuit Design - Incorporates safety mechanisms including anti-islanding detection, over/under-voltage protection. Islanding detection can be implemented through active frequency drift or voltage phase jump detection algorithms.

For graduation projects, models can be developed using PSCAD/EMTDC or MATLAB/Simulink simulation platforms. Research directions can extend to: Grid-connected stability under weak grid conditions Harmonic suppression in multi-inverter parallel operation Energy management strategies for photovoltaic-storage hybrid systems