Daniel Heredero-Peris

Inverter design for four-wire microgrids

This paper presents a PQ four quadrant four-wire three-phase inverter for microgrids integration. The inverter is based in two full-bridge IGBT modules connected in a three-phase configuration plus a three-phase parallelized neutral branch. This topology is galvanically isolated through a single-phase transformer bank. The converter operates as a non-ideal voltage-controlled voltage source inverter under AC droop strategy with hot-swap capability based on a dynamic virtual impedance.

Implementation of grid-connected to/from off-grid transference for micro-grid inverters

This paper presents the transfer of a microgrid converter from/to on-grid to/from off-grid when the converter is working in two different modes. In the first transfer presented method, the converter operates as a Current Source Inverter (CSI) when on-grid and as a Voltage Source Inverter (VSI) when off-grid. In the second transfer method, the converter is operated as a VSI both, when operated on-grid and off-grid. The two methods are implemented successfully in a real platform but the later offers some advantage.

Development and implementation of a dynamic PV emulator with HMI interface for high power inverters

In this paper a 10 kVA photovoltaic emulator is presented. The system implemented generates photovoltaic V-I characteristic curves to analyse and test maximum power point tracking algorithms of real photovoltaic inverters according to the standard EN50530. The power converter used includes a three-phase ac-dc active rectifier. The power stage selected allows to minimize the harmonic current content and permits to be closed to the unity power factor with a fast response. The emulator is controlled by a digital signal processor that communicates with a human-machine-interface. It allows to emulate static and dynamic responses. Furthermore, the interface is also capable of simulating weather evolution and situations under shaded conditions.

Electric vehicles in power systems with distributed generation: Vehicle to Microgrid (V2M) project

The integration of electric vehicles into distribution networks will require intelligent systems for managing the charging points and the impact on the grid. Electric vehicles represent an opportunity to manage the power demand allowing shifting the electric load to off-peak periods and to store the excess of generation from renewable generators. In addition, the electric vehicles could be used to improve the reliability and power quality if vehicle to grid (V2G) is deployed. The Vehicle to Microgrid (V2M), an Endesa Novare Award, consists on evaluating the impact of electric vehicles into the network and proposing solutions to deal with the challenges that electric vehicles introduce. The results will be validated in a demonstration plant that is a microgrid placed at IREC.

Demonstration and experience of the smart rural grid project

This paper aims to detail and illustrate the experiences for the grid-connected mode during the operational phase of the Smart Rural Grid (SRG) project. The SRG project is focused on DSOs capabilities to increase the interoperability, resilience, efficiency and robustness of the existing rural distribution network by the utilization of new Smart Grid technologies. This project is founded by the European Union and it is constituted by an eight partners consortium mixing their know-how in a hybrid smart solution; therefore, power electronics, control theory, telecommunications, distribution system operator energy managing, supervisory systems and end-users coexist in a pilot network. This pilot network includes four rural secondary substations up to 200 kVA interconnected by means of medium voltage rural overhead lines in Vallfogona, Catalonia, Spain.

Understanding the three and four-leg inverter Space Vector

This paper shows a new point of view of the classical voltage space vectors and its implications on three and four-leg converters. It is easy to find in the literature, authors using bi-dimensional and three-dimensional representations of the converter states. Nonetheless, the literature rarely specifies what these spaces represent. Therefore, this paper proposes a wide analysis of the state voltages and its references for three-leg, three-leg four-wire and four-leg inverters, in favour of understanding the space vector behaviour under three and four-wire scenarios.

Stability analysis of current and voltage resonant controllers for Voltage Source Converters

This paper presents an analytical development for the Nyquist trajectory of the closed loop system of a Voltage Source Inverter with resonant control strategy. Both inner current loop and outer voltage loop are taken into account, and the interaction between them is studied. The stability boundaries depending on different parameters are determined. Firstly, the system is modelled and analysed in continuous time. Secondly, the analysis is conducted in the discrete time domain. A numeric study supported with graphical representations is provided for complex analytic situations.

An anti-islanding method for voltage controlled VSI

Islanding detection methods have been widely applied and thought for current-controlled voltage source inverters, as in case of photovoltaic inverters. However, some considerations have to be taken into account when anti-islanding detection strategies are applied on voltage controlled-voltage source inverters, for example in case of using AC droop control. This paper shows different issues when anti-islanding algorithms based on the voltage and frequency displacements are used in voltage-controlled inverters. The impedance measurement of the point of common coupling is presented as a mechanism to achieve the islanding detection. An anti-islanding method for voltage-controlled voltage source inverters is proposed, and the suitable frequencies to be used are analysed. The concept of frequency detection band is defined allowing the impedance measurement to improve its behaviour towards resonant and non-resonant loads.

Design methodology for a dc–dc power conversion system with EIS capability for battery packs

Abstract This paper presents a design methodology for a dc-dc power conversion system (PCS) for battery packs. The methodology provides with an optimal design of the PCS and the associated inductive-capacitive filter interfacing the battery pack with the PCS. The PCS adds superior capability over conventional designs, which is performing current and voltage perturbations at the battery terminals for the so-called electrochemical impedance spectroscopy (EIS). This technique is an option for battery state-of-charge (SoC) and state-of-health (SoH) assessment. The design is optimal in the sense that it minimizes volume and system power losses. Such multi-objective optimization is addressed adopting the theory of weighted sum and Pareto front. The methodology is tested through a case study, addressing a lithium-ion battery pack. The offered analyses permit to identify the impact in system performance of diverse design variables such as dc-link voltage for the PCS and its switching frequency.

A novel fractional proportional-resonant current controller for voltage source converters

This paper proposes a hybrid controller that combines conventional proportional-resonant controllers with the more recent application of fractional order calculus applied to the current control loop of voltage source converters. The use of existing non-integer orders applied to proportional-integral controllers is extended to resonant controllers. The application of fractional exponents for the integro-derivative parts contributes with an extra degree of freedom that permits to enhance the obtained response in an extended frequency range when the closed-loop bode diagram is analysed. Different implementation alternatives in the continuous time domain are presented, and the most suitable one is selected. The new controller formulation capabilities are compared with conventional proportional-resonant controllers via simulations and its performance is validated in a test platform based on a 20 kVA silicon-carbide converter acting as an active filter.