Simulation of Harmonic Compensation using PR Controller for Three-Phase Grid-Connected Inverters

In power electronic systems, three-phase grid-connected inverters are commonly used devices for converting DC power to AC power and integrating it into the grid. To achieve high-quality grid current control, Proportional Resonant (PR) controllers are typically employed to regulate the inverter's output. When operating in the abc coordinate system, PR controllers can effectively track both fundamental and harmonic components of AC signals, thereby enhancing the system's dynamic performance and steady-state accuracy. Harmonic compensation represents a crucial functionality of PR controllers, where multiple resonant frequency points are introduced to suppress specific harmonic orders in grid currents, such as common low-order harmonics like the 5th and 7th. In simulation models, harmonic suppression effectiveness can be optimized by adjusting the resonant gains and resonant frequencies of the PR controller, effectively reducing Total Harmonic Distortion (THD). Implementation typically involves configuring resonant transfer functions for each target harmonic frequency in the control algorithm. The simulation typically includes the inverter main circuit, PWM modulation strategy, and the closed-loop control system with PR controllers. Through simulation analysis, the effectiveness of control strategies can be validated, and parameters can be optimized to enhance the inverter's grid-connected performance. Key simulation components often involve implementing PR controller transfer functions in discrete-time domain using methods like Tustin transformation, and designing harmonic extraction blocks for real-time harmonic detection and compensation.