Modeling, Control, and Experimental Evaluation of Multifunctional Converter System

Abstract

The multi-functional converter system (MFCS) is a special topology of three-phase AC motor drives, which inherently integrates a DC-voltage regulation function. Firstly, in order to explain the mechanism of the MFCS, an average model is derived. An equivalent circuit is developed, which explicitly reveals that the MFCS is equivalent to a cascaded DC/DC converter-DC motor drive system. Secondly, the inverter's mean duty-cycle is identified as an independent control degree of freedom for the DC-bus voltage. Then, the influence of pulse width modulation (PWM) on the DC-bus voltage is studied. It concludes that space vector PWM is invalid for the MFCS. To address this problem, the zero-sequence voltage injection PWM (ZSVIPWM) is proposed and actually sinusoidal PWM is a special case of the ZSVIPWM. Thirdly, an overall control strategy is proposed for the MFCS, which includes not only the vector control for the motor but also a closedloop control for the DC-bus voltage. Finally, comparative experiments with the standard topology are carried out on a permanent magnet synchronous machine prototype to verify these theoretical analyses and the control strategy.

A sliding mode‐based single‐loop control strategy for permanent magnet synchronous motor drives

“…The state vectors are defined by the output and control signal as y = x 1 and u = u q , respectively. From Equations ( 6) and (7), the general second-order system can be developed as:…”

“…However, PMSM drive systems are known to be non-linear and easily affected by variable conditions, that is, high temperature or external disturbances [4][5][6]. Field-oriented control (FOC) with a cascade structure is widely used in PMSM drives, where the outer speed loop and the two inner current loops are often implemented by conventional proportional-integral (PI) controllers [7,8]. The PI controllers may show slow response and high sensitivity to motor parameter variation at various operating conditions [9,10].…”