Arash A. Boora

Voltage-sharing converter to supply single-phase asymmetrical four-level diode-clamped inverter with high power factor loads

The output voltage quality of some of the single-phase multilevel inverters can be improved when their dc-link voltages are regulated asymmetrically. Symmetrical and asymmetrical multilevel diode-clamped inverters have the problem of dc-link capacitor voltage balancing, especially when power factor of the load is close to unity. In this paper, a new single-inductor multi-output dc/dc converter is proposed that can control the dc-link voltages of a single-phase diode-clamped inverter asymmetrically to achieve voltage quality enhancement. The circuit of the presented converter is explained and the main equations are developed. A control strategy is proposed and explained in details. To validate the versatility of the proposed combination of the suggested dc-dc converter and the asymmetrical four-level diode-clamped inverter (ADCI), simulations and experiments have been directed. It is concluded that the proposed combination of introduced multioutput dc-dc converter and single-phase ADCI is a good candidate for power conversion in residential photovoltaic (PV) utilization.

A general approach to control a Positive Buck-Boost converter to achieve robustness against input voltage fluctuations and load changes

A positive buck-boost converter is a known DC- DC converter which may be controlled to act as buck or boost converter with same polarity of the input voltage. This converter has four switching states which include all the switching states of the above mentioned DC-DC converters. In addition there is one switching state which provides a degree of freedom for the positive buck-boost converter in comparison to the buck, boost, and inverting buck-boost converters. In other words the positive buck- boost converter shows a higher level of flexibility for its inductor current control compared to the other DC-DC converters. In this paper this extra degree of freedom is utilised to increase the robustness against input voltage fluctuations and load changes. To address this capacity of the positive buck-boost converter, two different control strategies are proposed which control the inductor current and output voltage against any fluctuations in input voltage and load changes. Mathematical analysis for dynamic and steady state conditions are presented in this paper and simulation results verify the proposed method.

Applications of power electronics in railway systems

Power system interface with electrified railways (ER), auxiliary power, hybrid trains, electromagnetic interface (EMI) and traction are reviewed in this paper for diesel electric trains and ERs. Auxiliary power supply is a low voltage AC/DC power supply for onboard devices with an important consideration for safety equipment. In diesel electric railways because of variable train speed, a sort of compromise is taking place between traction and auxiliary power which usually affects auxiliary equipment performance. Hybrid trains energy storage unit can compensate this deficiency. Other challenges in railways are their compatibility with power and communication systems.

Bidirectional positive buck-boost converter

In a positive buck-boost (PBB) converter, inductor current and capacitor voltage can be decoupled which may improve system stability. In fact for a specific level of capacitor voltage, the inductor current can be adjusted at different levels and can be utilized to increase the robustness of the converter against input voltage and load disturbances. But when demand is a fast response with respect to step change in reference voltage, this topology needs to be modified. In this paper, a family of topologies based on a positive buck boost converter are presented which have a fast response and bidirectional power flow capability. This feature leads to some applications in hybrid vehicle systems and telecommunications. Simulations have been carried out to validate fast response of the proposed converters.

A new DC-DC converter with multi output: Topology and control strategies

This paper presents a new topology based on a Positive Buck-Boost converter with multi output (MOPBB). A single output positive Buck-Boost converter consists of a Buck and Boost converters in cascade which can be controlled against input voltage fluctuation and load changes. In this paper, the steady state and dynamic analyses of the proposed topology are presented along with simulation results. A control algorithm is presented to control output voltages against input voltage fluctuation and step change in load with a purely logic control system that is based on hysteresis current and voltage control. This topology is suitable for a high power multilevel converter with diode-clamped topology where a series of capacitors are required to generate different voltage levels and capacitors voltage control is an important issue in this application.

Efficient voltage/current spike reduction by Active Gate Signaling

This paper presents an Active Gate Signaling scheme to reduce voltage/current spikes across insulated gate power switches in hard switching power electronic circuits. Voltage and/or current spikes may cause EMI noise. In addition, they increase voltage/current stress on the switch. Traditionally, a higher gate resistance is chosen to reduce voltage/current spikes. Since the switching loss will increase remarkably, an active gate voltage control scheme is developed to improve efficiency of hard switching circuits while the undesirable voltage and/or current spikes are minimized.

Utilising Robustness of Positive Buck-boost Converter against Input Voltage and Load Current Disturbances

Abstract A positive buck-boost (PBB) converter is a known DC-DC converter that can operate in step-up and step-down modes. Unlike buck, boost and inverting buck-boost converters, the inductor current of a PBB can be controlled independently of its voltage conversion ratio. In other words, the inductor of PBB can be utilised as an energy storage unit in addition to its main function of energy transfer. In this paper, the capability of PBB to store energy has been utilised to achieve robustness against input voltage fluctuations and output current changes. The control strategy has been developed to keep accuracy, affordability and simplicity acceptable. To improve the efficiency of the system, a smart load controller (SLC) has been suggested. Applying SLC, extra current storage occurs when there is a sudden load change, otherwise little extra current is stored.