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- Item23-Level Inverter for Electric Vehicles Using a Single Battery Pack and Series Active Filters(IEEE, 2012) Pereda Torres, Javier Eduardo; Dixon, Juan
Show more Cascaded H-bridge (CHB) multilevel inverters have been conceived as an alternative to reduce total harmonic distortion (THD) in medium-voltage drives. The reduced THD makes them useful for electric vehicle (EV) applications, but the main problem with the CHB is the large amount of isolated power sources required to feed each of the H-bridges. An improved variant known as the asymmetrical CHB (ACHB) inverter uses H-bridges of different sizes and then needs fewer isolated power sources than the CHB. However, in battery-powered EVs, only one power supply (fuel cell or battery pack) is desirable. This work presents a solution to solve the problem, operating some of the small H-bridges (Aux-bridges) as series active filters and using a small high-frequency link (HFL). With this solution, only one dc source is required to feed the inverter, and if the control is adjusted to work at particular switching points, more than 98% of power is transferred through the larger H-bridges (MAIN bridges). The proposed ACHB topology can produce any number of levels, and the M AIN bridges always commutate at fundamental frequency. As the number of levels must remain constant for all output voltages, a variable dc source is required to control the amplitude of the motor voltage. This work shows some simulations and experiments on a 2-kW 27-level ACHB working with only 23 levels. The concept is being implemented in a small EV with an ACHB drive of 18 kW.Show more - ItemA clean four-quadrant sinusoidal power rectifier using multistage converters for subway applications(2005) Dixon, Juan; Morán, Luis
Show more A special 27-level four-quadrant rectifier for subway applications is analyzed. The arrangement uses only three H-bridges per phase, common dc bus, and independent input transformers for each H-bridge. The transformers allow galvanic isolation and power escalation to obtain high-quality voltage waveforms, with total harmonic distortion of less than 1%. Some advantages of this 27-level rectifier are: 1) only one of the three H-bridges, called the main converter, manages more than 80% of the total active power in each phase and 2) it switches at fundamental frequency, reducing the switching losses at a minimum value. The rectifier analyzed in this paper is a current-controlled voltage-source type, with a conventional feedback control loop. Some simulations in a rectifier substation, including power reversal at full load are displayed (750 Vdc, 1200 A). The rectifier shows the ability to produce clean ac and dc waveforms without any ripple, and fast reversal of power. Some experimental results with a small prototype, showing voltage and current waveforms, are finally displayed.Show more - ItemA new mathematic algorithm to analyze power distribution systems with active compensation and nonlinear loads(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2008) Mahomar, Jose; Moran, Luis; Guzman, Johan; Dixon, Juan
Show more This paper presents a new procedure to analyze power distribution systems that energize nonlinear loads. The algorithm uses the singular values of the transfer matrix that relates the output variables and the system perturbation. The algorithm is especially developed to analyze the compensation performance of shunt and series active power filters. The algorithm is proved by simulation in a multibus industrial power distribution system and programmed in Matlab.Show more - ItemA series active power filter scheme for current harmonic compensation(IEEE, 2008) Figueroa, Diego; Moran, Luis; Ruminot, Pedro; Dixon, Juan
Show more A series active power filter to eliminate current harmonic components and compensate reactive power is presented and analyzed. The proposed active compensation technique is based in a series active filter composed by two single-phase inverters sharing the same DC bus, and is suitable for current harmonics and reactive power compensation generated by static converters. The proposed approach allows for low cost, simplicity and part count reduction in comparison with previous compensation solutions (passive and active). The paper analyzes the proposed series active power filter in terms of principles of operation, power circuit topology, control design and implementation. Experimental results obtained in a laboratory DSP based controlled prototype confirm the viability of the proposed compensation technique.Show more - ItemCascaded Multilevel Converters: Optimal Asymmetries and Floating Capacitor Control(IEEE, 2013) Pereda Torres, Javier Eduardo; Dixon, Juan
Show more Cascaded multilevel (CM) converter is a series connection of several inverters that together generate multiple voltage levels with controllable frequency, phase, and amplitude. Its main advantages are high power, reliability, and power quality. However, it has considerable drawbacks such as high number of components, many isolated power sources, decreasing voltage quality with the modulation index, and regeneration in some series inverters at specific modulation indexes, even when the machine is motoring. The authors propose to improve any CM topology through two solutions: use optimal voltage asymmetries (ratios), higher than conventional ones; replace the voltage sources by floating capacitors balanced with a new control (PI controller) and/or a high-frequency link. This paper presents theoretical analysis and experimental results of CM converters with increased voltage-quality (levels), some of them keeping this high quality and avoiding regeneration in motor mode at any motor operation point, using the proposed voltage asymmetries and simplifying or eliminating some voltage sources. Experimental results show a reduction of components, an improved voltage quality, and a satisfactory behavior in stationary and dynamic operation.Show more - ItemCurrent control strategy for brushless DC motors based on a common DC signal(2002) Dixon, Juan; Leal, Iván A.
Show more A simplified current controlled modulation technique for brushless DC motors is presented. It is based on the generation of quasi square-wave currents, using only one current controller for the three phases. The advantages of this strategy are: (a) very simple control schemeShow more - ItemPWM Method to Eliminate Power Sources in a Nonredundant 27-Level Inverter for Machine Drive Applications(IEEE, 2009) Rotella Macchiavello, Mauricio Humberto; Penailillo Salgado, Gonzalo Eduardo; Pereda Torres, Javier Eduardo; Dixon, Juan
Show more A nonredundant three-stage 27-level inverter using ldquoHrdquo converters is analyzed for medium- and high-power machine drive applications. The main advantage of this converter is the optimization of levels with a minimum number of semiconductors. However, the system needs six bidirectional and isolated power supplies and three more unidirectional if the machine is not using regenerative braking. In this paper, these nine power supplies are reduced to only four, all of them unidirectional, using three strategies: 1) the utilization of independent and isolated windings for each phase of the motor; 2) the utilization of independent input transformers; and 3) the most important of them, the application of special pulsewidth modulation (PWM) strategies on the 27-level converter, to keep positive average power at the medium power bridges and zero average power at the low-power bridges. The generation of this PWM and control of this multiconverter was implemented using DSP controllers, which give flexibility to the system.Show more - ItemSensorless Control for a Switched Reluctance Wind Generator, Based on Current Slopes and Neural Networks(2009) Echenique Subiabre, Estanislao Juan Pablo.; Dixon, Juan; Cardenas, Roberto; Pena, Ruben
Show more In this paper, the analysis, design, and implementation of a novel rotor position estimator for the control of variable-speed switched reluctance generators (SRGs) are presented. The rotor position is obtained using the unsaturated instantaneous inductance. This unsaturated inductance is estimated calculating the slope of the phase current and using a reduced-size neural network (NN) whose inputs are the average current and the saturated inductance. The proposed estimator requires less processing time than traditional methods and can be fully implemented using a low-cost DSP with very few additional analog/digital components. The rotor position estimator presented in this paper can be applied to a wind energy conversion system where the SRG is used as a variable-speed generator. This application is currently being studied because the SRG has well-known advantages such as robustness, low manufacturing cost, and good size-to-power ratio. Simulation and experimental results are presented using a 2.5-kW 8/6-SRG prototype.Show more - ItemUltracapacitor-Based Auxiliary Energy System for an Electric Vehicle: Implementation and Evaluation(IEEE, 2007) Ortúzar Dworsky, Micah Etan; Moreno De La Carrera, Jorge Alejandro; Dixon, Juan
Show more In the search for better efficiency, an auxiliary energy system (AES) for electric vehicles (EVs) was designed, implemented, and tested. The system, which is composed of an ultracapacitor bank and a buck-boost converter, was installed in an EV, which is powered by a lead-acid battery pack and a 54-kW brushless dc motor. Two control strategies where developed: one based on heuristics and the other based on an optimization model using neural networks. These strategies were translated to algorithms and implemented in a digital signal processor, and their performance was evaluated in urban driving. The results were incorporated to an economic evaluation of the system, which shows that the reduction in costs would only justify the inclusion of this type of system in a lead-acid battery-powered vehicle if the battery life is extended by 50% or more, which is unlikely. The same results were extrapolated to a case in which the lead-acid batteries are replaced by a fuel cell. In this case, the costs of different power support systems were evaluated, such as ultracapacitors and high-specific-power lithium-based batteries. The results showed a significant cost reduction when AES configurations are included in contrast to a system powered by fuel cells only. Also, the cost reduction was higher when using ultracapacitors for this purpose.Show more