Improved Synchronized SVPWM Strategy for High-Power Three-Level Active Neutral Point Clamped Traction Inverter

The high-power three-level active neutral point clamped (3L-ANPC) traction inverter is employed in maglev train. During high-speed operation, the carrier ratio (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub>) is relatively low. To optimize the harmonic performance of the output voltage, an improved synchronized space vector pulsewidth modulation (ISSVM) tailored for the multisampling rate control system is proposed, which can achieve any phase voltage half-period pulse number under an integer multiple <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> of three. Through the proposed spectrum analytical method based on the 3L-ISSVM, the harmonic characteristics of the phase voltage are fundamentally analyzed. A smooth switching strategy for broadband multimode ISSVM by phase compensation and switching in a specific angle interval is introduced. The experimental results indicate that, compared to existing synchronized pulsewidth modulation strategies, the proposed ISSVM offers superior harmonic and dynamic performance. The switching between the two ISSVM strategies can be realized without two-level jump in phase voltage and simultaneous action in three-phase. It is well-suited for closed-loop control of synchronous motors across a wide frequency range.