Three-Phase Photovoltaic Inverter Islanding Simulation Including PWM Rectifier and PI Regulator

In photovoltaic power generation systems, islanding effect refers to the situation where the PV system continues to supply power to local loads when the grid power is interrupted. To ensure system safety, islanding simulation tests are essential.

The PWM rectifier plays a critical role in the simulation, converting DC power from the photovoltaic array into AC power suitable for the grid. Through pulse width modulation technology, it precisely controls the waveform of output voltage and current, maintaining synchronization with the grid. In code implementation, this typically involves generating PWM signals using timer interrupts or dedicated PWM modules, with switching frequencies typically ranging from 2-20 kHz depending on system requirements.

The PI regulator implements closed-loop control for the system. It dynamically adjusts the PWM duty cycle by performing proportional-integral operations on errors in voltage, current, and other parameters to ensure stable output. The selection of PI parameters (Kp and Ki) directly affects system response speed and stability, requiring iterative debugging and optimization through simulation. In simulation models, this is often implemented using difference equations: u(k) = Kp*e(k) + Ki*∑e(i) + u0, where anti-windup mechanisms are typically added to prevent integral saturation.

Islanding simulation also requires modeling grid disconnection detection logic, such as monitoring frequency or voltage variations to determine if the system has entered islanding mode, thereby triggering protection mechanisms. Common detection algorithms include phase jump detection, frequency shift monitoring, and harmonic analysis. This simulation is a crucial step in verifying the reliability of photovoltaic inverters, typically implemented through MATLAB/Simulink models or dedicated power electronics simulation platforms.