DC-link voltage control strategy of Z-source inverter for high-speed permanent magnet motor

In order to widen the flux-weakening range of motors, this study proposed a DC-link voltage control strategy for high-speed permanent magnet motor drive systems powered by Z-source inverter. In this strategy, the DC-link voltage, also known as the output voltage of the impedance network, varies with the inverter output voltage and remains optimal at all times, whether in steady state or transient state. As for the shoot-through duty ratio and the modulation index, the two main control variables in the Z-source inverter are under unified control to ensure the stability of the system, while achieving fast tracking and reducing the loss. In addition, a new sliding mode control system based on the indirect control of the capacitor voltage is used to control the DC-link voltage to suppress the system fluctuation caused by the change of the given value or the motor load. Besides, various conventional voltage Z-source inverter pulse width modulation strategies can be applied to this technology. Simulations and experiments verified the effectiveness of the proposed strategy.