In the thesis, the author focuses on solving three problems related to voltage source inverter(VSI) in general and VSI used in an electric and hybrid electric vehicle in particular. The first problem is related to the fact that using pulse width modulated (PWM) voltage to supply the motor causes a common-mode voltage (CMV) at the motor bearings. To solve this problem, a hybrid space vector PWM is proposed that reduces the CMV amplitude and frequency to the maximally allowable extent. This can be done by utilizing a special switching sequence that takes into consideration the phase angle between the load voltage and current. The second problem is related to the optimal PWM sequence that allows the elimination of selected low order odd harmonics. Previously, this optimization problem used to be solved using an offline approach. There have been several attempts to implement the control algorithm in realtime. All of the proposed methods in the literature, at some points, use initial guessing or iteration. This leads to an online approach with non-deterministic execution time and with the possibility to fail to reach convergence. The author shows that the optimal PWM can be implemented in realtime with deterministic execution time and without compromise. Furthermore, a significantly more generalized algorithm is proposed that allows the modulation of selected harmonics rather than merely eliminating them. The opportunities opened up by the generalized algorithm are limitless and currently being explored. The potential applications include wireless charging and digital wave generation. Modulation of several harmonics to arbitrarily prescribed values is impossible to implement using an offline approach. The third problem is to address the limitations associated with the fact that VSI is a buck converter. For applications where the available dc voltage is limited, an additional dc-dc boost converter is needed to obtain the desirable ac voltage. Commercial hybrid vehicles typically use an inductor based dc-dc converter to boost the voltage. At higher power, the dc-dc converter becomes inefficient. Therefore, the application of the boost stage is seen only in hybrid vehicles with a battery of a few kWh. The author proposes a new family of bidirectional dc-ac boost converters that utilizes a switched-capacitor network to boost the voltage. The switched-capacitor and the inverter are modulated as one unit, which allows the removal of the large output filtering capacitor and the reverse blocking diode required by a typical switched-capacitor converter. This effort results in extending the power level of switched-capacitor based converters from existing sub kW range to tens kW and beyond with much mitigated penalty on device utilization.
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