Three-phase boost-stage coupled current source inverter concept and its space vector modulation

The current source inverter (CSI) is essentially a converter with inherent boost capability and has been preliminarily applied in the field of renewable energy generation systems. However, conventional CSIs are mostly operated independently. Several existing multilevel CSI topologies entirely rely on parallel combinations, which seems to be not very suitable for capacity expansion. To solve this issue, this paper proposes a concept of three-phase boost-stage coupled current source inverter (BSC-CSI) through the duality principle, which can output multi-level currents with a reduced number of switches as well as hardware costs. Compared with the state-of-the-art CSIs, the proposed BSC-CSI can notably simplify the implementation of the multi-level modulation scheme and meanwhile ensure the power devices switch under lower current stress. To further take full advantage of the modularity and scalability, the BSC-CSI can be constructed by hybrid using silicon-carbide (SiC) and silicon (Si) based semiconductor switches for improving efficiency. The experimental results have verified the theoretical findings

Five-level current-source inverters with buck-boost and inductive-current balancing capabilities

This paper presents new five-level current-source inverters (CSIs) with voltage/current buck-boost capability, unlike existing five-level CSIs where only voltage-boost operation is supported. The proposed inverters attain self-inductive-current-balancing per switching cycle at their dc front ends without having to include additional balancing hardware or complex control manipulation. The inverters can conveniently be controlled by using the well-established phase-shifted carrier modulation scheme with only two additional linear references and a mapping logic table needed. Existing modulators can therefore be conveniently retrofitted for controlling the presented inverters. By appropriately coordinating the inverter gating signals, their implementations can be realized by using the least number of components without degrading performance. These enhanced features of the inverters have already been verified in simulation and experimentally using a scaled-down laboratory platform

Five-Level Current-Source Inverters With Buck–Boost and Inductive-Current Balancing Capabilities

This paper presents new five-level current-source inverters (CSIs) with voltage/current buck-boost capability, unlike existing five-level CSIs where only voltage-boost operation is supported. The proposed inverters attain self-inductive-current-balancing per switching cycle at their dc front ends without having to include additional balancing hardware or complex control manipulation. The inverters can conveniently be controlled by using the well-established phase-shifted carrier modulation scheme with only two additional linear references and a mapping logic table needed. Existing modulators can therefore be conveniently retrofitted for controlling the presented inverters. By appropriately coordinating the inverter gating signals, their implementations can be realized by using the least number of components without degrading performance. These enhanced features of the inverters have already been verified in simulation and experimentally using a scaled-down laboratory platform.\ud \u

High-performance motor drives

This article reviews the present state and trends in the development of key parts of controlled induction motor drive systems: converter topologies, modulation methods, as well as control and estimation techniques. Two- and multilevel voltage-source converters, current-source converters, and direct converters are described. The main part of all the produced electric energy is used to feed electric motors, and the conversion of electrical power into mechanical power involves motors ranges from less than 1 W up to several dozen megawatts

Power loss investigation of series-connected current source inverters

Current-source inverters (CSIs) are a type of direct current (DC) to alternating current (AC) converters that generate a defined AC output current waveform from a DC current supply. As the counterpart of voltage source inverters (VSIs), they feature a simple converter structure, low switching dv/dt on the ac-side, and reliable short-circuit protection. These advantages have made CSIs widely used in high power medium voltage drives. Besides, they have also been studied in other applications, such as wind energy conversion systems, superconducting magnetic energy storage (SMES) systems, and microgrid systems. Different topologies of CSIs and modulation schemes have been evolved to tailor various application requirements. For those applications with a higher power rating, two or more CSIs can be connected in series to form series-connected CSIs (SC-CSIs) to increase the power handling capability. To the best of the author’s knowledge, three topologies of SC-CSIs have been developed so far. The first topology referred to as topology A is constructed by connecting several identical CSIs in series. These CSIs are identical in terms of topology, modulation, and control. A multi-winding transformer is employed at the output to provide a clear current path for each CSI and step up the voltage if necessary. In the second topology designated as topology B, the multi-winding transformer is replaced by a phase-shifting transformer, and a phase-shifting modulation scheme is implemented. This topology features an increased DC current utilization, decreased switching losses, and reduced passive components. The third topology denominated as topology C adopts a different arrangement of switches leading to a reduced number of switching devices. A multi-winding transformer is used at the output in this topology. Power losses are an important attribute of SC-CSIs since they have a significant impact on the efficiency of the system. Besides, it is necessary to find out the power loss distribution of inverters to design an appropriate cooling system. However, the power losses and the power loss distribution of these three topologies have not been figured out. [...

Current fed multilevel converters for high current power applications

Phd ThesisThe majority of the worldwide installed power inverters today are voltage source inverters followed by current source inverters where the concluding decision lies with the performance of the applications besides the usual economic reasons. Recent active development in the current source inverter areas has seen the emerging of various generalized multilevel current source inverter topologies analogous to the existing multilevel voltage source inverter families. To date, the multilevel current source inverter families have been classified principally by the physical appearance of their basic structures and also by the number of current sources employed. The existing multilevel current source inverter topologies are unpopular for present applications due to reasons such as big sizes, high control complexity and low reliability; which circumstances are often associated to massive component counts and multiple requirements of current sources. Therefore, this research has been focused on the single-phase single-source generalized multilevel current source inverter for this apparent advantage; where this thesis proposed a novel generalized multilevel current-source inverter topology with the lowest component utilization while employing just a single current source. In addition, the proposed topology can conveniently achieved dc current balance with a simple low frequency switching strategy for the five- and nine-level current outputs. From comparison analysis, the proposed topology has significantly less number of components employed compared to the nearest topology, which implies low implementation cost. The experimental results verify the characteristics and performances of the proposed topology acquired by computer simulations.ministry of education, Malaysia and also to my employer the University Malaysia Pahang (UMP) for the financial suppor

Optimization of a CSI inverter and DC/DC elevator with silicon carbide devices, for applications in electric traction systems

The applications of electric traction systems currently focus on developing technologies with greater energy efficiency and lower environmental impact. Manufacturers of hybrid and electric vehicles are looking for ways to improve and optimize the efficiency of their models. Manufacturers are looking for more efficient and more compact converter topologies. The use of new band gap materials in the construction of these topologies has generated many debates and new lines of research especially in the optimization of these topologies. The silicon carbide (SiC) based switching devices provide significant performance improvements in many aspects, including lower power dissipation, higher operating temperatures, and faster switching, compared with conventional Si devices, all these features make that these devices generate interest in applications for electric traction systems. This work presents a method for improving total harmonic distortion (THD) in the currents of output and efficiency in SiC current source inverter for future application in an electric traction system. The method proposed consists in improving the coupling of a bidirectional converter topology V-I and CSI. The V-I converter serves as a current regulator for the CSI and allows the recovery of energy. The method involves an effective selection of the switching frequencies and phase angles for the carriers signals present in each converter topology. With this method, it is expected to have a reduction of the total harmonic distortion THD in the output currents. In addition, an analysis of the losses in the motor and topologies of power converters is developed considering the optimization method previously analyzed. The weighted average efficiency of the whole system (power converters + motor) in differents conditions of operations is presented.Las aplicaciones de los sistemas de tracción eléctrica actualmente se centran en el desarrollo de tecnologías con mayor eficiencia energética y menor impacto ambiental. Los fabricantes de vehículos híbridos y eléctricos están buscando formas de mejorar y optimizar la eficiencia de sus modelos. Los fabricantes buscan topologías de convertidores más eficientes y más compactas. El uso de nuevos materiales de banda prohibida en la construcción de estas topologías ha generado muchos debates y nuevas líneas de investigación, especialmente en la optimización energética de las mismas. Los dispositivos de conmutación basados en carburo de silicio (SiC) proporcionan mejoras significativas en la eficiencia en muchos aspectos, incluida una menor disipación de potencia, temperaturas de funcionamiento más altas y una conmutación más rápida, en comparación con los dispositivos de Si convencionales. Todas estas características hacen que estos dispositivos generen interés en las aplicaciones de sistemas tracción eléctrica. Este trabajo presenta un método para mejorar la distorsión armónica total (THD) en las corrientes de salida y eficiencia en el inversor de fuente de corriente SiC para aplicaciones futuras en un sistema de tracción eléctrica. El método propuesto consiste en mejorar el acoplamiento de una topología de convertidor bidireccional V-I y CSI. El convertidor V-I sirve como un regulador de corriente para el CSI y permite la recuperación de energía. El método implica una selección efectiva de las frecuencias de conmutación y los ángulos de fase para las señales portadoras presentes en cada topología del convertidor. Con este método, se espera una reducción de la distorsión armónica total THD en las corrientes de salida. Además, se desarrolla un análisis de las pérdidas en el motor y las topologías de los convertidores de potencia considerando el método de optimización analizado previamente. Se presenta la eficiencia promedio ponderada de todo el sistema (convertidores de potencia + motor) en diferentes condiciones de operaciónPostprint (published version