Performance evaluation of current control strategies in LCL-filtered high-power converters with low pulse ratios

In this paper, four current control strategies for voltage source PWM inverters with LCL-filter at extreme low pulse ratios (e.g. 80 Hz load frequency/600 Hz carrier frequency) are investigated. The system is a medium-voltage variable frequency drive (VFD) application with the power rating over 20 MW. The benefits and drawbacks of each scheme are summarized to provide a guideline for the current control loop design. The stability, dynamic response and the resonance damping effect of passive or active damping strategies are analyzed via a precise double-sided frequency modeling method. The system cost, algorithm complexity and dynamic performance are considered as well. Besides, analysis methodology based on the double-sided spectrum for such applications is demonstrated. Finally, the results have been validated in time-domain simulations.