Jeronimo Quesada

Approaching hybrid wind-diesel systems and controller area network

High wind penetration hybrid wind-diesel systems have complex control requirements. The random nature of the wind, the cubic velocity to power relationship and the fast response of wind turbines make control goals like maintain system stability, and prescribed power quality levels, not easy to achieve. This paper deals with how to implement a distributed control system based on the controller area network (CAN) in hybrid wind diesel systems with high wind penetration. Firstly some introduction to hybrid wind-diesel systems is presented. Secondly two architectures for such hybrid systems are presented and studied mainly from the control point of view. This study concludes with a need of a distributed control, and the definition of some sensor and actuator nodes in the system. The CAN bus is used to close one of the several regulation loops presented. Some considerations about real time distributed control like clock synchronization among nodes when using CAN bus are presented. Finally some advantages of using CAN with such hybrid systems are outlined.

Determination of vitamins D2, D3, K1 and K3 and some hydroxy metabolites of vitamin D3 in plasma using a continuous clean-up–preconcentration procedure coupled on-line with liquid chromatography–UV detection

A semi-automatic procedure for the continuous clean-up and concentration of several fat-soluble vitamins prior to their separation by HPLC and UV detection is reported. The procedure is based on the use of a minicolumn packed with aminopropylsilica as sorbent located prior to the chromatographic detection system. The overall process was developed and applied to the main liposoluble vitamins (A, D2, D3, E, K1, K3) and several hydroxy metabolites of vitamin D3 [25-(OH)-D3,24,25-(OH)2-D3 and 1,25-(OH)2-D3]. All the analytes were monitored at a compromise wavelength of 270 nm. Calibration graphs were constructed between 0.01 and 100 ng ml-1 for vitamin D2 and D3 and their hydroxy metabolites, between 0.1 and 100 ng ml-1 for vitamin A, K1 and K3 and between 1 and 100 ng ml-1 for vitamin E, with excellent regression coefficients (> or = 0.9901) in all cases. The precision was established at two concentration levels with acceptable RSDs in all instances (between 3.6 and 8.7%). The method was appropriate for the determination of vitamin D2, D3, K1 and K3 and the 24,25-dihydroxy and 25-hydroxy metabolites of vitamin D3 in human plasma. The method was applied to plasma samples spiked with the target analytes and the recoveries ranged between 78 and 109%.

Well-known serial buses for distributed control of backup power plants. RS-485 versus controller area network (CAN) solutions

Networking is increasingly becoming a feature of industrial products such as those for medical devices, vending machines, machine tool, and, the example analyzed here, modular power plants. As many such systems depend on cheap microcontrollers, a common approach to networking has been based on the combination of the available standard serial communication controller (UART) normally included in such devices and RS-485 drivers. However UART-based network protocols do have some potential disadvantages. Controller area network (CAN) offers an attractive alternative due to the availability and low cost of CAN based devices. This paper compares these two approaches in the design of a serial bus, devoted to internal interconnection in a commercial range of modular power backup systems, and describes the migration process from the first to the second solution.

Decoupled droop control techniques for inverters in low-voltage AC microgrids

This paper discusses the droop control method for inverters participating in low voltage microgrids and its application as a primary control layer which can be actuated from a secondary control layer to dispatch active and reactive power. To that end, an independent and decoupled relationship between frequency and active power; and voltage and reactive power is desirable. When the classic droop control method is applied to inverters connected to the microgrid through RL type impedance, this decoupled actuation is lost. Different variants of decoupled techniques are presented and analyzed from the point of view of static and dynamic behavior. The analysis is supported on a linear dynamic phasor model of the droop controlled inverter, and verified by simulations of behavior in an isolated microgrid and in grid tied mode using a detailed SIMULINK/SimPowerSystems model of the inverter and its internal control. Among the diverse techniques, the recently proposed droop control method with dynamic decoupling is signaled as advantageous, not only in terms of decoupled actuation but also in flexibility in adjustment of static and dynamic response.

Decoupled droop control of inverters

This article first reviews the droop control method for inverters participating in low voltage microgrids, discussing static and dynamic response. Then the paper proposes a droop controller that brings independent actuation of frequency over active power and voltage over reactive power. The method is based on the application of a matrix filter that decouples dynamic actuation and reduces the multivariable system to two independent single input-single output systems. The results of static, dynamic and robustness analysis are given, with a discussion of simulation results. An advantage of this method is that the control loop can be stabilized and tuned by specifics gain parameters that are independent of the droop coefficients and of the coupling impedance of the inverter with the grid. It thus offers maximum freedom and flexibility for adjusting the static and dynamic behavior of droop control.

A systems theory perspective of electronics in engineering education

We briefly review fundamental concepts related to systems theory and systems engineering. We also review and structure a list of important properties for an electronic system and paradigms and techniques applicable to analysis and design. Then we present two specific case studies, in which the systems theory approach to electronics engineering teaching and research has been very influential.

Combining moodle and redmine as e-learning tools in Project Based Learning of Industrial Electronics

This paper reports on the application of the Project Based Learning (PBL) methodology in the teaching of Electronics Instrumentation to undergraduate students using as e-learning platforms the well-known Moodle framework and Redmine, a project management web application. In this PBL implementation each student group develops a different measurement or data acquisition project over the course of an entire academic term, maintaining customer-provider relationships with other groups. In this context, Redmine complements Moodle by providing dynamic time tracking and task management capabilities. In addition PBL is enriched by introducing the students to the use of a project management application.

Knowledge management and professional profiles in electronic systems engineering: The function of university-industry collaboration

This paper presents a work in progress related to the knowledge and competence management techniques applicable in an electronic systems engineering company. It also discusses the role of the university-industry collaboration in the knowledge management process.

Application of real-time fault-tolerant distributed control in parallel operation of inverters

This article presents a study on the application of distributed fault-tolerant real-time control for the parallel operation of single-phase inverters integrated in modular uninterruptible power supplies (UPS) or Battery Energy Storage Systems (BESS). The inverter controllers run the fundamental control tasks in synchronization with each other to create a replica determinate set. Control of the parallel inverters follows an active load sharing scheme supported over a digital real-time fault-tolerant control layer. Each inverter applies a Smith predictor for delay compensation and a Kalman observer to estimate output current. Thus the set of parallel inverters behaves as an AC source with low output impedance, whereas the output current is shared equally between the inverters, avoiding circulating currents. Variants and extensions of the method are also proposed. The paper concludes by discussing grounds for standardizing a distributed real-time control layer for modular converter systems.

A Multidisciplinary PBL Approach for Teaching Industrial Informatics and Robotics in Engineering

This paper describes the design of an industrial informatics course, following the project-based learning methodology, and reports the experience of four academic years (from 2012–13 to 2015–16). Industrial Informatics is a compulsory course taught in the third year of the B.Sc. degree in industrial electronics and automation engineering at the University of the Basque Country (UPV/EHU), Spain. The course had students develop an embedded controller for a 2DoF SCARA robot that drew a specific trajectory. The robot was built with the LEGO Mindstorms kit and the controller was implemented with NXC, a C-like programming language for the NXT brick. In this activity, students became aware of their learning needs and had to work proactively, both autonomously and in teams. The course design achieved several objectives: 1) students learned the course material; 2) soft skills demanded by employers were reinforced; and 3) the material was structured into project tasks for students to perform. The article analyses two indicators: 1) qualification marks and 2) student satisfaction.