Adaptive Closed Loop State Control System for a Three-Level Z-Source Inverter

In electric vehicles abrupt torque steps and changing driving speeds require alternating currents and voltages. The battery voltage varies depending on the state of charge and on operation points. In order to keep the DC voltage of the Three-Level Inverter constant or conform it to the induced voltage of the electric machine (M) to reduce switching losses a DCDC converter is necessary. An alternative to the just mentioned configuration is the Three-Level Z-Source Inverter (3LZSI) that facilitates to boost the DC voltage or keep it constant. The control path has a nonlinear behavior. To design a closed loop state control system and calculate the control parameters the control path has to be linearized by a Taylor series. If the operating point deviates from the approximate steady-state value the system behavior of the control system differs from the assumed one. In order to achieve the desired dynamic system behavior the controllers' parameters have to be adapted in each operation point. In this paper an adaptive closed loop state control system for a 3LZSI is presented. The control system only requires the magnitude and the angle of a voltage vector by way of example the reference torque and electrical angle of a machine. Furthermore if it is necessary the control system initiates the boost of the DC voltage without making any additional arrangements.