Jose Restrepo

This work presents the result of employing a custom test-rig, designed for education and research, for teaching the control of synchronous generators in interconnected micro-grids. The teaching approach used allows implementing innovative teaching activities with experimental experiences, useful as support tool for courses in control, electronics, power electronics, and control of electrical machines. The developed test-rig was used in a postgraduate and undergraduate power electronics courses, with two different approaches: as student-run platform, and demonstrative practices managed by professors. The training activities using the test-rig platform has been evaluated by a owndesigned surveys. The results shown satisfactory effectiveness in aspects as relevance, learning assistance, contextualization of real problems, among others.

Interior permanent magnet synchronous machine drives are widely employed in electric traction systems and various industrial processes. However, prolonged exposure to high temperatures while operating can demagnetize the permanent magnets to the point of irreversible demagnetization. In addition, direct measurements with infrared sensors or contact-type sensors with wireless communication can be expensive and intrusive to the motor drive systems. This paper thus proposes a nonintrusive thermal monitoring scheme for the permanent magnets inside the direct-torque-controlled interior permanent magnet synchronous machines. By applying an external high-frequency rotating flux or torque signal to the hysteresis torque controller in the motor drive, the high-frequency currents can be injected into the stator windings. The permanent magnet temperature can thus be monitored based on the induced high-frequency resistance. The nonintrusive nature of the method is indicated by the elimination of the extra sensors and no hardware change to the existing system. Finally, the effectiveness of the proposed method is validated with experimental results.

This paper presents a communications test-rig based on a customized Intelligent Electronic Device (IED) for its use in a laboratory-scale microgrid. The laboratory setup for this work uses the following three types of subsystems: distributed energy resources DERs (solar, wind), energy storage (batteries) and loads (active, reactive, linear and nonlinear). A Raspberry Pi computer, using the Linux operating system, allows programming the algorithms needed by the communications platform. The protocol employed for data exchange, between the different subsystems and the central supervisor module, is the IEC 61850 standard. Three experimental test cases serve to show the proposed IEDs performance. The first test transfers data between a solar source and a client station. The second test transfers data, in distributed mode, between four nodes associated to different generation sources. The last test shows a secondary control using two experimental inverters operating in parallel connection. The IEDs communicate the compensating values for regulating frequency and voltage in the system composed of a master and one or more slave inverters.

High speed switched reluctance machines (SRMs) are gaining popularity in both academia and industrial communities. One of the reasons that limit the maximum speed of SRMs is the speed limit of commercial rotary encoders due to mechanical considerations. In this paper, a novel direct position control for ultra-high speed SRMs is proposed based on non-intrusive reflective sensors. It uses reflective optical sensors to detect the relative position between the rotor and the stator so as to control the on and off states of the switches directly through the analog output trigger signals generated by the optical sensors. In order to generate the maximum output torque, the switching-on and -off angles are optimized based on the equivalent Simulink model with the torque and flux linkage characteristics obtained from a corresponding finite element analysis (FEA) of a high speed SRM. Finally, the proposed method is validated by experiments with a 500 W 4/2 SRM running up to 100,000 rpm. The proposed control system has many advantages such as low cost and virtually no speed limit, which makes it suitable for ultra-high speed applications.

This paper presents an investigation of a three-phase squirrel-cage induction machine (IM) with inter-turn short-circuit (ITSC) fault driven by Direct Torque Control (DTC). DTC is the most typical driver for controlling IM's torque and flux in industrial applications. Also, DTC has been classified as a non-linear hysteresis-based predictive controller. Two state-space (SS) models for the asymmetric IM are presented. The first model uses flux-linkages and the second one uses currents as SS variables. The advent of these models is to provide flux and currents vectors information to calculate the angle difference between the trajectories of constant torque and constant stator flux amplitude, expressed as a function of the inverter voltage components. Additionally, errors in the estimated torque and flux are found throughout mathematical models that explains the DTC reaction to the ITSC effects. Simulation and experimental results are conducted for the asymmetric IM driven by DTC to observe the limits of the controller and to corroborate their theoretical impacts which in future research could be utilized for ITSC fault detection.

This work presents three fuzzy variable structure control (FVSC) techniques applied to the current control loop in a three-phase synchronous rectifier. These techniques are based in a Takagi-Sugeno (T-S) fuzzy PI controller. The first controller is a first-order FVSC, used as a reference. Then, two FVSC strategies are presented and tested, a second and a third-order FVSC. These control schemes are first simulated and then tested in a general-purpose laboratory synchronous rectifier test bench. Experimental results show that control performance is good in all three schemes, achieving current harmonic compensation and power factor correction.

El trabajo presenta el desarrollo de un banco de emulación de perfiles de viento, incluyendo el sistema de conversión de energía eólica a energía eléctrica. El banco completo de emulación consta de un elemento motriz, encargado de proporcionar perfiles pares/velocidad, correspondientes a datos reales de disponibilidad eólica de un lugar geográfico particular. El elemento motriz, constituido en este banco de emulación por un motor de corriente continua de 3.3 kW, se acopla al elemento generador, en este caso una máquina de rotor bobinado (DFIG por sus siglas en inglés), de 4.0 kW @ 50 Hz. Las máquinas eléctricas se alimentan a través de un sistema de potencia compuesto por un puente rectificador y un puente H, para la máquina de corriente continua, y un convertidor dual en configuración “back to back” para la máquina de inducción de rotor bobinado. Los elementos conmutadores del sistema de potencia son módulos duales de transistores bipolares de compuerta aislada (IGBT). Se utilizan dos bloques disipadores de calor, uno para el conjunto rectificador/puente-H, y otro para el convertidor dual. La velocidad del eje del conjunto de máquinas se mide utilizando un codificador óptico. Las señales necesarias para el control, del sistema emulador, se miden mediante dos tarjetas de sensores de tensión/corriente, con capacidad para medir 16 señales en total. Para el control de los convertidores se utiliza una tarjeta basada en un arreglo de lógica programable (FPGA) interconectada con un procesador digital de señales (DSP) que permite la alta velocidad de procesamiento requerida para probar distintas técnicas de control. El convertidor es controlado por modulación de ancho de pulso (PWM) conmutando a una frecuencia ajustable, en este caso se selecciona una portadora de 10kHz.

This work presents the design and development of a three-phase multilevel hardware platform for applications in power electronics. The emphasis of the proposed converter is in its flexibility to allow rapid set-ups of different experiments typically required in power electronics teaching and research. The proposed converter uses a cascaded H-bridge topology whereby multilevel operation with up to 9 voltage levels can be obtained. The selected power stage topology as well as the control, drivers and sensors boards designs, enable the platform to operate in multiple configurations, namely as inverter, controlled rectifier or active power filter, for one, two or three-phase systems.