MATLAB Code Implementation for Photovoltaic Inverter Simulation

Implementation of photovoltaic inverter simulation in MATLAB primarily involves the following key steps: Photovoltaic Array Modeling First, establish a mathematical model of photovoltaic cells, typically using single-diode or double-diode equivalent circuits. The model must account for the effects of factors such as light intensity and temperature on output characteristics, reflecting nonlinear behavior through I-V and P-V curves. In MATLAB code, this can be implemented using lookup tables or mathematical equations like the Shockley diode equation, where parameters like photocurrent and diode ideality factor are calibrated based on manufacturer datasheets. Inverter Topology Selection Common topologies include single-phase full-bridge or three-phase inverters. During simulation, build corresponding models of switching devices (such as IGBTs or MOSFETs) and configure PWM modulation strategies (like SPWM or SVPWM) to generate target output voltage waveforms. Code implementation often uses Simulink's Simscape Electrical library to model switching components and generate PWM signals with carrier comparison techniques. Grid-Connected Control Strategy The core involves dual-loop voltage and current control: Outer voltage loop control: Regulates DC bus voltage stability, typically using a PI controller. In MATLAB, this can be implemented with the pid function or Transfer Function blocks to maintain constant DC-link voltage under varying solar conditions. Inner current loop control: Tracks grid current commands through PR (Proportional Resonant) or repetitive controllers to achieve unity power factor grid connection. The PR controller implementation requires resonant terms tuned to grid frequency using transfer functions with high gain at specific frequencies. Harmonic Suppression Design Harmonic compensation can be added to the current loop, such as designing resonant controllers for specific harmonics (like 3rd, 5th, 7th) or attenuating harmonics near switching frequency through filters (LCL type). Code implementation involves adding parallel resonant controllers for targeted harmonics or designing LCL filter parameters using impedance matching calculations. Simulation Verification Build a complete system in MATLAB/Simulink to test dynamic response (like power regulation during sudden light changes), THD (Total Harmonic Distortion), and compliance with grid standards (such as IEEE 1547). Use Powergui tools for FFT analysis and scopes to monitor waveform quality and system stability. Extension Ideas: Combine with MPPT algorithms (like Perturb and Observe) to maximize photovoltaic output using incremental conductance methods coded with conditional statements and sampling loops. Add islanding protection logic using voltage/frequency detection algorithms to enhance safety. Compare different control strategies (such as droop control for microgrid applications) by implementing multiple controller variants and analyzing performance under load variations.