Abstract:

To investigate the intrinsic characteristics and DC bus voltage control strategy of the capacitor voltage reduced quasi Z-source three-level inverter, the basic principle of the inverter is first analyzed. Then, the state space averaging method and small signal disturbance method are used to model the DC side of the Z-source network, and the transfer function from the through duty cycle to the capacitor voltage of the quasi Z-source network is derived, providing a theoretical basis for the optimal selection of DC side parameters and the design of control systems. Finally, a voltage current dual loop control system for the inverter is designed, which indirectly controls the DC bus voltage and maintains a constant output voltage of the inverter, with good steady-state and dynamic performance. The correctness of the small signal model and the rationality of the control system are verified.

Key words: quasi Z-source three-level inverter, quasi Z-source network, neutral point clamped, small signal model, voltage and current dual-loop control