Enhanced Real-Time-Update Current Control for LCL-Filtered Grid-Connected VSCs

Control delay plays an important role in the stability of grid-connected voltage source converters (VSCs), and the critical value is one quarter of switching period (0.25T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sw</inf> ) based on the passivity-based stability theory. However, the control delay is 1.5T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sw</inf> and 0.75T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sw</inf> for the regular single-sampling and double-sampling pulse width modulation (PWM), respectively, and there will be a large non-dissipative region in the high-frequency range. To tackle this challenge, an enhanced real-time-update PWM is proposed and the control delay can be kept to 0.25T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sw</inf> . Moreover, compared with the conventional real-time-update PWM, the duty cycle is not limited and the grid-side current quality is similar. Finally, the simulation verifies the effectiveness of the proposed method.