Current source inverters (CSIs) represent an attractive alternative to conventional voltage source inverters in high-frequency applications, owing to their reduced output voltage stress and inherent short-circuit protection. However, the mandatory insertion of overlap time between switching states, required to guarantee a continuous current path for the DC-link inductor, introduces non-linear distortions into the synthesized output currents. These distortions strongly depend on the adopted space vector modulation (SVM) strategy and can significantly degrade the power quality and efficiency of the conversion system.
This paper presents an overlap time compensation methodology applicable to a wide range of carrier-based SVM strategies for CSIs. A unified classification framework is first introduced to uniquely identify switching patterns based on the number of segments and dwell time sequences. Building on this representation, the overlap time effects are analytically characterized by linking dwell time variations to the instantaneous phase voltage relationships. The proposed compensation algorithm performs an online correction of the dwell times, restoring the ideal reference current vector independently of the selected SVM pattern.
The effectiveness of the proposed approach is validated through comprehensive simulation and experimental investigations conducted on an induction motor drive. The conversion system was implemented with a DC–DC converter pre-stage supplying the CSI. The motor test bench consisted of an induction motor mechanically coupled to a DC motor, where the former controlled the torque and the latter regulated the speed. The results demonstrate a substantial reduction in low-order harmonic distortion in both output currents and voltages, with THD reductions of up to 90% for certain modulation strategies. Furthermore, the effective amplitude modulation index is recovered, achieving the required output current level, and the overall conversion efficiency improves, with measured gains of up to two percentage points.
