Research On The Controller Of High-Performance Z-source Inverter In Hybrid Electric Vehicle

Due to the an imperative need about efficient, low-cost and reliable of DC/DC converter and inverter for hybrid electric vehicle (HEV) system, high-performance Z-source inverter (HP-ZSI) could be suitable and reliable solution for HEV system and it could completely replace the traditional DC/DC converter and inverter. Compared to the traditional DC/DC converter and inverter, HP-ZSI has the advantages as:does not require dead-time to protect short circuit, can buck and boost the output voltage with a single stage, produce any desired output AC voltage and reduce in-rush and harmonic current. This dissertation focused on the HP-ZSI research and has completed the following works:After the basic theory of HP-ZSI introduced and the main parameters of HP-ZSI designed, the prominent characteristics of the shoot-through modified space vector pulse width modulation (MSVM) control method compared to the shoot-through simple boost control (SBC) in term of the harmonic performance features and boost-buck capability were presented in this dissertation. The comparison results informed that the shoot-through MSVM control would be suitable for the peak DC-link voltage (PDV) control in HP-ZSI.Under the variation DC-input voltage, parameters of Z-source network and parameters of induction motor, the output voltage stabilization of HP-ZSI is very important to improving the quality of the motor speed control as well as increasing performance of electric drive vehicle. Therefore, design study to choose a suitable control strategy for the PDV plays an important role for satisfying requirements of HP-ZSI system. Because of the DC-link voltage (DCV) characteristics of HP-ZSI, the DCV cannot be controlled directly but it should be controlled by adjusting the PDV. The PDV is calculated by combination of capacitor voltages of Z-source network and shoot-through duty ratio based on basic principle of the HP-ZSI. Moreover, designing a suitable controller for the PDV affects total harmonic distortion of current and the quality of the speed motor. Therefore, this dissertation also presents comparisons of the different control techniques such as fuzzy logic controller (FLC), self-tuning fuzzy PI controller (SFP) from the point of response speed and current total distortion magnitude in order to choose the most suitable technique for controlling PDV. Results show that the FLC is the best quality as compared to SFP and PI controller.The closed-loop speed control of induction motor based on the combining of direct torque control and MSVM (DTC-MSVM) has many exceptional features such as fast torque response, low steady state torque ripple, high accurate, output voltage stabilization in the inverter bridge, which will satisfy requirements of HEV system. In order to improve the performance of inductor motor in HEV system, the adaptive control technique for controlling speed of induction motor will be needed to cope with the parameters variation and conditions variation. The aim of this dissertation is to propose the adaptive control technique for speed of induction motor as self-tuning fuzzy PI controller (SFP). This technique can adjust gains of PI controller online according to variations of motor parameters and load torque relied on fuzzy rules. This dissertation also presents comparisons and evaluations of SFP with the other intelligent control techniques as genetic algorithms optimal tuning gains of PI. These evaluations are implemented base on criterion of the integral of the absolute value of speed error. This criterion is closely related with the performance index of the system. Results illustrate that the SFP shows good robustness against motor parameter variation and it is suitable for controlling speed of induction motor.These methods are verified by simulation and experiment implementation using Matlab software and dSPACE DS1103hardware, respectively.