Space Vector Phase Disposition-Pulse Width Modulation and Multiband Hysteresis Through Digital Implementation for a Type-G Converter: A Comparative Study

In the last decades, aiming to control some processes and improve high-power system efficiency, multilevel converters have been commonly applied in adjustable-speed and high-performance drives in the mining and petrochemical industries. Although they present operational advantages over the classic two-level topology in high-power and medium-voltage applications, the implementation of their current control still has some issues that deserve additional studies. In this line, this work presents a comparative study of two current control techniques for a five-level neutral point clamped (NPC) inverter for induction motor drives: 1) linear current control with space vector pulse width modulation (SV-PWM) command (normally applied in commercial drives) and 2) nonlinear digital hysteresis current control. A multiband (MB) switching frequency limiter is presented in this article for the last technique. The multilevel power electronic converter investigated here is an NPC converter known as a
type-G converter
. Some challenges for the implementation of digital MB hysteresis are discussed. In this article, a digital signal processor (DSP) is selected for both strategies, while a field-programmable gate array (FPGA) is employed to implement the frequency-limiting circuits and switching logic of the digital hysteresis control. In both cases, the drive operates under the indirect implementation of rotor field-oriented control (RFOC). Simulation results obtained from PLECS and experimental results in a 2-hp laboratory prototype are presented and discussed.