Bidirectional Quasi Z Source Inverter with Fuzzy Logic Controller for Traction Motor Speed Control

Abstract

The Fuzzy Logic Controller is implemented to control the speed of the electric vehicle applications. The speed and output voltage of the motor, controlled by Proportional Integral (PI) controller and Fuzzy Logic Controller can be compared. During starting and braking of the electric vehicle applications the performance comparison is done. The reverse power flow is obtained by Bidirectional Quasi-Z-source inverter (BQ-ZSI). The inverter with the design and operation is analyzed. The Electric vehicles and hybrid electric vehicles are emerging vehicles in the future generation. The power flow and speed can be controlled during starting and braking of the vehicles .The comparison of the speed control using PI and Fuzzy controller is done and output results. The simulation results are presented to prove the functionality of the circuit and the effectiveness of the proposed control strategy. Index Terms: Bidirectional quasi-Z-source inverter (BQ-ZSI), electric vehicle (EV) applications, feed-forward compensation, reverse power flow, small signal model. I. Introduction The evolution of Electric Vehicles (EV) creates a global push and provides better replacement of the fuel based vehicles. The Vehicles are charged by batteries and the power flow during starting and braking operations can be designed by Bidirectional quasi Z Source Inverter. The power (SDP) by 15% over the dc-dc converter with the VSI topology, which reduces the total cost and further improves the efficiency of the traction drive system . However, the input current of ZSI is not continuous, which will shorten the lifetime of the battery pack and degrade the vehicle performance. By rearranging the components in the Z-source network, a new topology called quasi-Z-source inverter (QZSI) is proposed. The QZSI realizes the continuous input current, at the same time retaining all the merits of the ZSI, which makes it a good candidate for EV applications. However, the traditional QZSI only allows unidirectional power flow from the dc to the ac side. The traction drive system requires the reverse power flow to realize the regeneration break of the EV. To achieve the bidirectional power flow capability, the same approach as in is utilized and the diode in the quasi-Z-source network (QZSN) is replaced by an active switch. A similar approach is also utilized in the bidirectional ZSI .However, much of the previous operation mode analysis was based on the topology of the ZSI and mainly focused on the power flow from the dc to the ac side. To better understand the circuit, this paper first gives a detailed circuit analysis of the bidirectional quasi-Z-source inverter (BQ-ZSI) during the regeneration mode, i.e., when the power flows from the ac to the dc side. The analysis proves that with the active switch, the inductor currents in the QZSN can be reversed and the energy from the ac side can be delivered to the dc source. The analysis also shows that, unlike in the ZSI, part of the dc link ripple current will be absorbed by the two capacitors in the QZSN and not go through the dc source, which provides a better operating condition for the battery pack in EV. Furthermore, with the additional switch, the discontinuous conduction mode (DCM) can be avoided and the BQ-ZSI can have a better performance with small inductance or under low power factor condition, such as when the electric motor is operated with a light load. Based on the circuit analysis, the small signal model can be obtained, and the control algorithm of the BQ-ZSI in EV applications can be developed. By rearranging the components in the Z-source network, a new topology called quasi-Z-source inverter (QZSI) is proposed. The QZSI realizes the continuous input current, at the same time retaining all the merits of the ZSI, which makes it a good candidate for EV applications.