Fermín Barrero-González

Power Injection System for Grid-Connected Photovoltaic Generation Systems Based on Two Collaborative Voltage Source Inverters

This paper presents a new topology for the power injection system that is based on the parallel association of two voltage source inverters. One operates using a quasi-square voltage waveform strategy, and the other operates with a pulsewidth-modulation (PWM)-based strategy. The aims of this topology are to inject the power from the photovoltaic generation system using the quasi-square inverter and to control the current quality using the PWM inverter. The proposal optimizes the system design, permitting the reduction of system losses and an increase of the energy injected into the grid.

Hybrid Multiconverter Conditioner Topology for High-Power Applications

A novel multiconverter conditioner topology and its control stage are proposed in this paper. It is formed by an active conditioner in parallel with a hybrid conditioner composed of an active filter in series with one or more passive filters. This topology allows the reduction of the inverter ratings, constituting an effective solution at high-power levels. Collaborative control strategies are developed for the new topology, which share the compensation objectives between the two converters. These control strategies and the tracking techniques are based on estimating the load current, achieving new algorithms with a reduction in the number of meters in the control stage. The conditioner operates properly in three-phase four-wire systems reducing the harmonic distortion and/or imbalance and attaining the unity displacement power factor. Experimental results are included for the testing of the topology and its control.

Novel method for synchronization to disturbed three-phase and single-phase systems

An autoadjustable synchronous reference frame for extracting the positive-sequence fundamental component of the voltage in the point of common coupling is proposed in this paper. It operates suitably under unbalanced and distorted input voltages, with no steady state error in amplitude, phase and frequency tracking. The dynamic response of the method in case of frequency or amplitude variations is good, achieving the steady state in only two cycles of the fundamental period. The method allows a simple adaptation for being used in single-phase systems too. Simulation and experimental results are presented to test the novel method.

A new criterion for selecting the inductors of an Active Power Line Conditioner

This paper analyzes the inductances used at the terminals of an Active Power Line Conditioner (APLC) based on a voltage source inverter (VSI) in some current correction topologies. The criteria to select the optimal inductances values are determined and a novel design criterion, named “control criterion”, is proposed. This novel method is applied to situations where there are sharp current variations as the case of a three phase rectifier feeding a resistive load. A parametrical analysis of the expressions obtained for the inductors is performed, obtaining the intervals of possible values of inductance that can meet the initial specifications. Finally a simulation is carried out to verify how the method presented reaches these specifications.

A Grid Connected Photovoltaic Inverter with Battery-Supercapacitor Hybrid Energy Storage

The power generation from renewable power sources is variable in nature, and may contain unacceptable fluctuations, which can be alleviated by using energy storage systems. However, the cost of batteries and their limited lifetime are serious disadvantages. To solve these problems, an improvement consisting in the collaborative association of batteries and supercapacitors has been studied. Nevertheless, these studies don’t address in detail the case of residential and large-scale photovoltaic systems. In this paper, a selected combined topology and a new control scheme are proposed to control the power sharing between batteries and supercapacitors. Also, a method for sizing the energy storage system together with the hybrid distribution based on the photovoltaic power curves is introduced. This innovative contribution not only reduces the stress levels on the battery, and hence increases its life span, but also provides constant power injection to the grid during a defined time interval. The proposed scheme is validated through detailed simulation and experimental tests.

Overview of plug-in electric vehicles as providers of ancillary services

Proliferation of plug-in electric vehicles obviously involves an interesting potential of electric energy storage for purposes related to smart grids. Among other opportunities, the possibility of providing ancillary services to the distribution grids they are connected to is evaluated in this paper as an added advantage of this kind of vehicles. Issues like aggregation needs, incentives, coordination with the aggregation manager and generation of setpoints, as well as the charging/discharging constraints of PEV batteries depending on the task to be performed are addressed, as an overview of the most recent literature related to the subject.

A Smart Power Electronic Multiconverter for the Residential Sector

The future of the grid includes distributed generation and smart grid technologies. Demand Side Management (DSM) systems will also be essential to achieve a high level of reliability and robustness in power systems. To do that, expanding the Advanced Metering Infrastructure (AMI) and Energy Management Systems (EMS) are necessary. The trend direction is towards the creation of energy resource hubs, such as the smart community concept. This paper presents a smart multiconverter system for residential/housing sector with a Hybrid Energy Storage System (HESS) consisting of supercapacitor and battery, and with local photovoltaic (PV) energy source integration. The device works as a distributed energy unit located in each house of the community, receiving active power set-points provided by a smart community EMS. This central EMS is responsible for managing the active energy flows between the electricity grid, renewable energy sources, storage equipment and loads existing in the community. The proposed multiconverter is responsible for complying with the reference active power set-points with proper power quality; guaranteeing that the local PV modules operate with a Maximum Power Point Tracking (MPPT) algorithm; and extending the lifetime of the battery thanks to a cooperative operation of the HESS. A simulation model has been developed in order to show the detailed operation of the system. Finally, a prototype of the multiconverter platform has been implemented and some experimental tests have been carried out to validate it.

Power injection system for photovoltaic plants based on a multiconverter topology with DC-link capacitor voltage balancing

This paper presents the simulation of a new topology for the power injection system of a single-phase grid connected photovoltaic generation system that is based on the parallel association of two voltage source inverters: one is a 3 level neutral point clamped operated using a low switching frequency strategy and the other is a 2 level inverter which operates with a pulse width modulation based strategy. The aim of this topology is that multilevel inverter injects the power and the other inverter controls the current quality. The DC-link capacitor voltage balancing is solved by using the redundant states of the multilevel inverter. The proposal optimizes the system design, allowing high power injection, permitting reduction of system losses and an increase of the energy injected into the grid.

Power injection system for photovoltaic generation plants with active filtering capability

A single-phase power injection system for photovoltaic generation plants based in two collaborative inverters is presented in this paper. The first converter works as a quasi-square waveform inverter with the main objective of injecting the energy produced by the photovoltaic generation system. The second converter acts as an active power filter with the objective that the current that flows from or to the grid is sinusoidal. The presented power injection system will be able to achieve a sinusoidal current even when a non-linear load is connected to the same point of common coupling. The performance of the proposed system, including the maximum power point tracking algorithm, is evaluated through simulation.

Active and reactive power control strategies for electric vehicles in smart grids

Electric vehicles (EV) can be used as distributed energy storage devices to provide to the smart grid different regulation services. However, to have enough impact in the grid, the trend is to jointly manage a set of EV by means of a new stakeholder called aggregator. Knowing the availability, mobility habits, and the state of charge (SOC) of each EV battery, the aggregator performs the allocation of an active and/or reactive set-point to each EV within a time slot. This paper aims to propose reference charger currents for each EV from the individual set-point received by an aggregator. Control strategies for bidirectional active power control are compared under ideal and distorted source conditions. Besides, to contribute to reactive power support and voltage control in the bus where the set of EVs are connected, a reactive control strategy is proposed and validated by simulation. The proposed control strategies are applied to a Mode 2 single-phase EV battery charger connected to a single-phase grid. Simulation tests have been conducted using different control strategies and active/reactive set-points provided by the aggregator.