Pulse width modulation (PWM) rectifiers are extensively used in battery charger, regulated dc voltage source, UPS systems, ac line conditioner and motor drives. The conventional control schemes for these rectifiers require PLL, transformations, and input voltage sensing, which increase the cost and complexity of the controller. Simple control schemes based on resistance emulation control are developed in this thesis work for different PWM boost rectifiers. Modeling, analysis and design methods for these rectifier systems are presented. The effect of computational delay involved in digital implementation on the performance of the above rectifier systems is studied. A single-switch boost rectifier system is presented, which operates in DCM and in CCM for an output power less than and greater than 50% rated load, respectively, exploiting the best features of both the operating modes. A generalized feedforward control is presented to improve the dynamic response of output voltage of single-phase boost rectifiers against input voltage, load current and reference voltage disturbances. Feedforward control requires additional voltage and/or current measurements. A state observer is presented for estimating the inductor current of a buck rectifier, and two disturbance observers are presented to estimate the input voltage and the load current of a boost rectifier. These observers eliminate the need of additional sensors for implementing the feedforward control. The resistance emulation control is extended to four-wire PWM rectifier. Two control methods are presented. The first method makes the input currents of the rectifier proportional to their respective input voltages, while the second one balances its input currents even under unbalanced input voltage condition. A detailed analysis of line and neutral current distortions of four-wire converter is presented. A three-carrier based PWM scheme is presented, which significantly reduces the neutral current of the rectifier compared to conventional PWM scheme, when three single-phase inductors are used, and considerably reduces both line and neutral current distortions, when a three-limb inductor is used. A regenerative test setup containing two back-to-back connected three-phase PWM converters is presented for testing high-power converters in the active and reactive power circulation mode. The proposed scheme considerably reduces the cost of testing, and hence, the overall production cost of the converters compared to load-bank testing. A mathematical model is presented for the above system. A suitable control method is presented to control the two converters of the back-to-back system. A new PWM scheme is presented, which considerably reduces the requirement of the dc bus voltage of the back-to-back system compared to conventional PWM schemes. All theoretical predictions are experimentally validated. The experimental results are presented.

The use of insulated-gate bipolar transistor (IGBT)-based power converters is increasing exponentially. This is due to high performance of these devices in terms of efficiency and switching speed. However, due to the switching action, high frequency electromagnetic interference (EMI) noises are generated. Design of a power converter with reduced EMI noise level is one of the primary objectives of this research. The first part of the work focuses on designing common-mode (CM) filters, which can be integrated with differential-mode (DM) filters for three-phase pulse-width modulation (PWM) rectifier-based motor drives. This work explores the filter design based on the CM equivalent circuit of the drive system. Guidelines are provided for selection of the filter components. Different variants of the filter topology are evaluated to establish the effectiveness of the proposed topology. Analytical results based on Bode plot of the transfer functions are presented, which suggest effective EMI reduction. Experimental results based on EMI measurement on the grid side and CM current measurement on the motor side are presented. These results validate the effectiveness of the filter. In the second part of the work, it is shown that inclusion of CM filters into DM filters results in resonance oscillations in the CM circuit. An active damping strategy is proposed to damp the oscillations in both line-to-line and line-to-ground ac voltages and currents. An approach based on pole placement by state feedback is used to actively damp both the DM and CM filter oscillations. Analytical expressions for state-feedback controller gains are derived for both continuous-and discrete-time models of the filter. Trade-off in selection of the active damping gain on the lower-order grid current harmonics is analysed using a weighted admittance function method. In the third part of the work, single-phase grid-connected power converters are considered. An integrated CM filter with DM LCL filter is proposed. The work explores the suitability of PWM methods for single-phase and parallel single-phase grid-connected power converters. It is found that bipolar PWM and unipolar PWM with 180◦interleaving angle are suitable for single-phase and parallel single-phase power converters, respectively. The proposed configuration along with the PWM methods reduces the CM voltage, CM current, and EMI noise level effectively. It is also shown that the suggested circuit is insensitive to nonidealities of the power converter such as dead-time mismatch, mismatch in converter-side inductors, unequal turn on and turn off of the switches, and propagation delays. In the fourth part of the work, the inter-phase inductor in parallel interleaved power converters is integrated with LCL filter boost inductor. Different variant designs are presented and compared with the proposed structure. It is shown that the proposed structure makes use of standard core geometries and consumes lesser core material as well as copper wire. Hence, it reduces the overall size and cost of the power converter. In the present work, a 10kVA three-phase back-to-back connected with input LCL filter and output dv/dt filter, a 5kVA single-phase grid-connected power converter with LCL filter, and a 7.5kVA parallel single-phase grid-connected power converter with LCL filter are fabricated in the laboratory to evaluate and validate the proposed methods. The experimental results validate the proposed methods that result in significant EMI performance improvement of grid-connected power converters.