Circuit Structure and Mathematical Model of Grid-Connected Inverters under Voltage Control Mode

Based on analyzing the circuit structure and mathematical model of grid-connected inverters operating under voltage control mode, we propose a photovoltaic inverter grid-connection control strategy employing repetitive control technology. This comprehensive strategy addresses critical aspects of grid synchronization including voltage regulation, current control, and frequency stabilization through embedded algorithms that utilize internal model principles for periodic signal tracking. The controller implementation typically involves a plug-in repetitive compensator structure with a fundamental period delay element (z^(-N)) in the feedback path to eliminate steady-state errors for grid harmonics. Our extensive simulation studies using MATLAB/Simulink models and experimental validations confirm the strategy's effectiveness in meeting grid-connection requirements across various photovoltaic module configurations. Notably, the control scheme demonstrates high efficiency and stability while reducing system costs and energy consumption through optimized switching patterns and harmonic suppression techniques. The strategy provides significant technical support and theoretical foundation for photovoltaic power generation systems, featuring real-time implementation capabilities through DSP-based digital controllers with precise sampling interval calibration for grid synchronization.