Haritza Camblong

Transient Operation of a Four-Leg Inverter for Autonomous Applications With Unbalanced Load

In this paper, the transient operation of a four-leg inverter equipped with an innovative control strategy under unbalanced load conditions is investigated. The inverter is proposed for transformerless hybrid power system applications, in order to provide simultaneous supply of three-phase and single-phase AC loads with balanced voltage and constant frequency. The four-leg inverter is controlled to ensure balanced voltage by means of a control strategy based on the decomposition of the supply three-phase voltage and current into instantaneous positive, negative, and homopolar sequence components using phasor representation. These three sequences are controlled independently in their own reference frames as DC signals. The implementation derived for the controller design is also described. The transient operation performance of the proposed control strategy has been tested in simulations with an average model and experimentally using a laboratory prototype.

Hybrid Energy Storage Systems for renewable Energy Sources Integration in microgrids: A review

The increasing use of the Renewable Energy Sources (RES) and the intermittency of the power generated by them create stability, reliability and power quality problems in the main electrical grid. The microgrid is called to be a feasible alternative to solve these issues. As it is a weak electrical grid, the microgrid is very sensitive to load or generation changes. To reduce the effect of these variations and to better harness the energy generated by RES, the Energy Storage Systems (ESS) are used. As the different ESS technologies that are currently available are not enough to satisfy the wide frequency spectrum of the generated energy, the use of a Hybrid Energy Storage System (HESS) is necessary. A HESS is usually formed by two complementary storage devices that can be associated in many different topologies. Of course, the two devices have to be coordinated by an Energy Management System (EMS). In this paper the different topologies and energy management algorithms that have been applied in the RES and microgrid contexts have been analysed and compared. A review of the latest papers related to the use of HESS to facilitate the integration of the RES in the microgrid context is carried out. Some examples of the (hybrid) electric vehicles are also addressed, as the use of the HESS is more extended in this field than in the field of the microgrids.

Digital control of a three-phase four-leg inverter under unbalanced voltage conditions

In this paper, the implementation of an innovative inverter control strategy based on the symmetrical components is presented. Symmetrical components of the inverter output voltage and current are decomposed into dq DC quantities to control a three-phase four-leg inverter. This kind of inverter can be a good choice for the applications with hybrid power system based on renewable energy used to supply unbalanced loads. The addition of a fourth leg provides an extra degree of freedom, making possible to handle the neutral current caused by the unbalanced load. Simulation results are compared with experimental results for a prototype inverter to verify the validity of the proposed control strategy.

An Innovative VSI Controller for the Generation of Balanced Voltage in Spite of the Presence of Unbalanced Loads

The aim of this paper is to present an innovative controller for a four-leg voltage source inverter (VSI) which allows generating a balanced voltage under unbalanced load conditions. The designed innovative controller contains four differentiated part. The first part decomposes three-phase unbalanced signals in three three-phase balanced signals. The second part projects these signals on to a rotating reference frame fixed to the voltage phasor. Then, the third part consists on the regulation of the voltage and current components represented in this frame by cascade control systems and PI controllers. Finally the outputs of the PIs are processed by a 3D space vector modulation algorithm to generate the duty cycles corresponding to the desired output VSI voltage. Some results of trials realized in steady and transient load conditions show the effectiveness of the innovative controller compared to a classical one.

Small-scale test bench of a hybrid power system

The study of behaviour of the hybrid power systems (HPS) for remote areas is one of research axes of our laboratory. Simulink blocks with models corresponding to all the system parts have been developed. Control laws have been implemented to ensure the optimal power retrieval, the system stability and the output power quality. In order to make possible the models and the control laws validation, a small scale HPS (1:100 of power) is under construction. It is composed of renewable sources (a wind turbine <WT> generator and photovoltaic <PV> panels), buffer batteries, DC/DC and DC/AC converters, diesel generator and load/faults emulator. For the system development some stages is necessary. Beginning with a simple starting structure, in every step a part is added or changed and the system operation is verified

Physical Workbench for Technical Training in Discrete Time Control

Abstract The aim of this paper is to present the BANCO project and its first results. ESTIA had not experimental setups to make work labs in the discrete-time control courses. It is why some Alecop setups have been improved to use them in these work labs. They were prepared to be used in the Control courses of the second and the third year. The made improvements concern especially an electronic module and its programming. This module allows the students to implement discrete-time control algorithms and to observe the behaviour of some real thermal, hydraulic and mechatronic processes. The main hardware parts of this module designed and constructed in ESTIA are a microcontroller card and a signal shaping card. In addition, the module communicates with a PC in order to program it. Experimental results obtained with a discrete time R-S-T control algorithm programmed in the module are compared to those obtained with an analog PI controller already existing in the Alecop setups. Now, the setups are being improved even more in order to be able to change some parameters of the processes and to apply systems identification algorithm to these processes.