The promising quasi-Z-Source inverter (qZSI) can regulate the DC-link voltage. In the study, a permanent magnet synchronous motor (PMSM) drive system is established with the qZSI. Based on the small-signal model, a feedback and feedforward compound control strategy is proposed and the dynamic performance of the converter is analyzed. The simulation and experimental results indicate that the compound control strategy effectively improves the static and dynamic characteristics of the DC-link voltage and reduces the influence of power variation on the DC-link voltage.

Introduction

A traditional motor drive system generally uses the battery plus voltage source inverter (VSI) to supply power [1], [2]. In order to raise the DC bus voltage, a cascaded DC-DC converter is often provided between the battery and the inverter [3]. In the system, the upper and lower switches of the same bridge arm cannot be turned on simultaneously. However, under complex working conditions, various disturbances may cause the switch mis-conduction and impair the reliability of the converter. To avoid the shoot-through state, it is necessary to add dead time, which brings out impulses in motor torque and harmonic loss increment and decreases the whole efficiency [4], [5]. The Z-Source inverter (ZSI) can function as both booster and inverter and replace the cascade system composed of the DC-DC converter and the VSI [6]. In addition, it can adjust the DC-link voltage and allow the shoot-through state. Compared with cascaded DC-DC systems, the ZSI is a single-stage system with higher reliability. However, it has the disadvantages of high voltage stress and discontinuous input current. Various impedance source inverters have been proposed. The trans-ZSI [7] and 0-ZSI [8] replace traditional ZSI inductors with double-winding transformer and reduce the number of capacitors to one. The trans-ZSI inverter maintains the high voltage boosting ability while ensuring the advantage of low voltage stress. With the increase in the shoot-through ratio, the voltage boosting ability of the 0-ZSI gradually decreases. T-ZSI [9] adopts the double-winding inductance coupling technology, which also reduces the numbers of inductors and capacitors to one.