Víctor Miñambres-Marcos

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.

Active functions implementation in smart inverters for distributed energy resources

In this paper are described some active functions that can be implemented in the inverters that interface the distributed energy resources to the grid can implement. These inverters are mainly placed in the grid for injecting the energy produced by the distributed generation, but they can do more than that taking advantage of their distributed location, being possible to control locally the power quality, to monitor electric magnitudes and reacts quickly to any event, or even to determine the grid state by characterizing disturbances or abnormal situations.

Three-phase single stage photovoltaic inverter with active filtering capabilities

This paper presents a study about the power injection of grid connected photovoltaic plants when there are non-linear loads connected to the point of common coupling. The smart grid scenario suggests that the photovoltaic energy should take care not only about the active power, but also about the reactive power. The study compares the last years criteria of injecting the maximum active power, with the expected tendency of providing reactive power in an active filter way for avoiding currents harmonics in the grid. The topology used is a traditional three-phase inverter controlled by a power balance technique through a synchronous hysteresis band. First of all, a power injection system that do not care about the loads connected into the grid is developed, then the loads are taken into account to improve the grid operation by supplying them. Both configurations are implemented in a prototype to compare the results via experimental tests.

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.

Grid reactive power compensation by using electric vehicles

Along this paper, it will be presented how the Electric Vehicle (EV) bidirectional chargers can help the Distribution Grid. In addition to the battery charge and the Vehicle-to-Grid functions (V2G), the reactive power can be compensated according to an established reactive power reference. A three-phase bidirectional inverter connected with a DC link to a DC/DC bidirectional converter is utilized in the topology. The different modifications that are needed in the control algorithm and in the power stage are determined. Simulation results are shown, which prove how the reactive power is being compensated and the saturation of the reactive current is used to keep the power under predefined limits.

Three-Level Neutral-Point-Clamped Quasi-Z-Source Inverter with Maximum Power Point Tracking for Photovoltaic Systems

This article is focused on a photovoltaic system based on the three-level neutral-point-clamped quasi-z-source inverter. The maximum power point tracking (MPPT) algorithm based on dP/dV feedback was used in the photovoltaic system to adjust the duration of the shoot-through states of power switches and achieve a maximum power. Proper system operation in the case of irradiance step is demonstrated by simulation in Matlab/Simulink software.

Point of common coupling voltage regulation with photovoltaic power plant infrastructures

This paper presents a point of common coupling voltage regulation technique by using a photovoltaic power plants generation system for controlling not only the injection active power but also the balance reactive power. The need of this functionality becomes true when some countries propose the use of renewable energy to help the grid when a sag is detected as a new standard. However, the idea is extensible to Smart-Grids where the power balance must be provided by the distributed generation. Active power injection is developed by a reference power point tracking and reactive power regulation by controlling the node voltage, both with dq current control with the different power priority possibilities. The studied topology is based on a single-stage traditional inverter but the control algorithm philosophy is valid for any topology. The whole system has been simulated in order to validate the control algorithm and tune the controller for obtaining the best transient response with zero steady state.

Three-phase regenerative electronic load to test shunt power conditioners

A 3-phase regenerative electronic load to test shunt equipments such as active power filters and power conditioners at high power levels is presented in this paper. The electronic load is composed by two inverters with a common DC-bus. One inverter draws from the grid a configurable load current with the harmonic and imbalance desired levels, and the other one is used to inject the energy into the grid trying to minimize the losses, while the active filter performance is being tested. The control strategies and the current controller for both inverters are explained. Simulations and experimental results showing the proper operation of the electronic load to test shunt power conditioners are presented.

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.

Development of a Photovoltaic Array Emulator in a Real Time Control Environment Using xPC Target

This paper is devoted to the design and construction of a photovoltaic array emulator for high power applications in order to test all kind of photovoltaic inverters. To develop such device, a rapid prototyping tool based on xPC Target of Matlab/Simulink has been used, providing a real-time testing environment. PV array emulator can be used to evaluate the performance of photovoltaic inverters as any test conditions can be programmed. The proposed emulator operates as a distributed control system taking advantage of the TCP/IP protocol features.