Pedro Rodriguez

Loyola University Andalucia · Engineering

Grid-forming power converters (GFMC) have been widely adopted in power systems as an attractive solution against the challenges imposed by the ever-increasing penetration of renewables. Despite its versatility, GFMC is employed only to provide islanded operation, grid regulations, and synthetic inertia. To further extend the use of GFMC in enhancin...

The advent of renewable energy has posed difficulties in the operation of power systems whose net inertia is becoming critically low. To face such challenges, grid-forming power has been one of the potential solutions pursued by the industry and research community. Though promising, grid-forming power converters are still immature for mass deployme...

The increasing participation of renewables in power systems has forced system operators to strengthen grid codes requiring renewable power plants (RPPs) to provide fast frequency support such as inertia response and power oscillation damping. To cope with such new requirements, this article proposes the implementation of a virtual synchronous power...

The proliferation of grid-connected converter interfaced energy sources in Smart Grids, enhance sustainability and efficiency as well as minimizing power losses and costs. However, concerns arise regarding the stability and reliability of future smart grids due to this wide integration of power electronic devices, which are recognized to affect the...

Series connections of modules in cascaded multilevel converters are prone to power imbalances due to voltage differences on their DC side. When modules are connected to direct current (DC) sources, such as photovoltaic panels, the capability of withstanding power imbalances is crucial for generating the maximum power. In order to provide a possible...

The presence of power electronics in today’s power systems strengthens due to the wider integration of renewable energy and energy storage systems. Subsequently, the dynamical response becomes harder to model and understand. As a possible solution, coherency identification, among other applications, can reduce complexity. However, conventional tool...

The integration of non-synchronous generation units and energy storage through power electronics is introducing new challenges in power system dynamics. Specifically, the rotor angle stability has been identified as one of the major obstacle with regards to power electronics dominated power systems. To date, conventional power system stabilizer (PS...

The integration of renewable energies based on photovoltaic power plants is increasing exponentially fast. In consequence, stability problems associated to the lack of inertia is becoming a serious concern. Transmission and distribution system operators are demanding more requirements in photovoltaic plants to provide grid functionalities in terms...

The series-connection of modules in multilevel converters are prone to energy imbalances in the dc capacitor due to the differences between the power absorbed and consumed. In renewable energy applications where the primary source is directly connected to each module, energy imbalances can be even worse if the primary sources are affected by unpred...

The objective of this article is to evaluate the spread of the virus and estimate the cases of infected population in need of urgent hospitalization, in order to provide sufficient resources to public health. To this end, a deep learning tool based on deep neural networks (DNN) was developed to predict COVID-19 infection and the need for urgent hos...

Nowadays the interest in grid-supporting energy storage systems for frequency response improvement is spurred to increase the penetration of renewable energy resources. Operational frequency constraints of the grid code should be fulfilled in the combined state feedback frequency control provided through the BESS frequency support and UFLS relays....

Energy Storage Systems installed at primary substations can be used by different participants of the power system for handling the emerging uncertainties caused by supply-side variations, demand-side flexibility and grid topology changes. This work presents a practical design for the monitoring system of the controller of the grid interactive energ...

Power systems with renewable sources are undergoing various changes to safely accommodate higher share of renewables. In this process, they require different changes ranging from technical characteristics to regulations. In order to manage technicality of the integration of the renewables, storage units play an important role. On the other hand, ma...

During the late months of last year, a novel coronavirus was detected in Hubei, China. The virus, since then, has spread all across the globe forcing Word Health Organization (WHO) to declare COVID-19 outbreak a pandemic. In Spain, the virus started infecting the country slowly until rapid growth of infected people occurred in Madrid, Barcelona and...

Grid operators require grid connected RGUs to provide specific dynamic features. RGUs must support dynamic performance of grid and operate in such a way to ward off new issues in grid. Recently, unfavorable oscillatory modes have appeared through grid connection of RGUs due to their dynamic interaction with other classical components of grid. There...

This paper presents a robust voltage sensorless control scheme to eliminate the need of line-voltage sensors in an LCL-filtered grid-connected inverter system. The proposed control scheme is based on an extended-state estimator structure which consists of a state feedback regulator and an estimator. The main contribution of this study relies on the...

This paper presents a network clustering (NC) method for active distribution networks (ADNs). Following the outage of a section of an ADN, the method identifies and forms an optimum cluster of microgrids within the section. The optimum cluster is determined from a set of candidate microgrid clusters by estimating the following metrics: total power...

The variable and unpredictable behavior of renewable energies impacts the performance of power systems negatively, threatening their stability and hindering their efficient operation. Flexible ac transmission systems (FACTS) devices are able to emulate the connection of parallel and series impedances in the transmission system, which improves the r...

The secure operation of power systems should be maintained into secure states under different grid impact events. Such operational and non-operational grid states events occur infrequently, but when they do, they reveal the dynamics of the system and the need for security strategies to counteract events such as cascading failures. The coherency gro...

Grid-connected power converters that integrate frequency support and inertia emulation functionalities have emerged in the last years. These features are promising for renewable energy based power generation plants, as it permits such systems to contribute to enhance the power system stability. This paper discusses about three different active powe...

The papers in this special section focus on power conversion and control in photovoltaic power plants. The power grid is undergoing significant changes with the rapid adoption of renewable energy. Solar power generation, and photovoltaics (PV) in particular, has been one of the fastest growing sectors in the power industry and has now reached price...

This paper presents a Unified Power Flow Controller (UPFC) application of the Custom Power Active Transformer (CPAT); a power electronics integrated transformer which provides services to the grid through its auxiliary windings. The CPAT structure integrates three single-phase transformers into one shunt-series combining transformer. This integrati...

Multilevel converters are widely used in medium and high voltage applications. Their high performance, power quality, efficiency and smaller filters make them interesting for renewable energy distribution systems. In utility- scale photovoltaic plants, these topologies could provide multiple benefits since they are able to connect string of photovo...

In modern power systems the increasing penetration of renewables and power electronics, particularly converter-based wind and solar power generation, is transforming system dynamics and bringing new stability concerns. One major issue that is currently attracting considerable attention is the wide range of power oscillations associated with renewab...

This paper proposes a cascaded single phase multilevel inverter using an off-the-shelf three-phase inverter and transformer. The concept is based on a cascaded connection of two inverter legs using a typical three phase inverter in such a way that the third leg is shared between the other two phases. The cascaded connection is achieved through an i...

This paper proposes a novel configuration for photovoltaic applications based on a cascade converter topology. The series connection between modules is achieved through the magnetic core of the integrated series transformer, therefore an inherent isolation is provided without the requirement of a dc-dc conversion stage. Such isolation approach betw...

Phasor measurement units and wide area measurement systems are becoming more and more popular due to their capability to record operational data with high sampling rates. By storing and processing this large amount of data, faster and more reliable approaches can be developed that overcome some of the drawbacks of traditional methods, such as respo...

To address continuously varying operating conditions in a power system with intermittent energy sources, the system should demonstrate certain level of flexibility. This paper identifies the parameters affecting flexibility in a power system and proposes an optimization model to study various impacts of these parameters. In this regard, storage, as...

As power systems become more complex in order to accommodate distributed generation and increased demand, determining the stability status of a system after a severe contingency is becoming more difficult. To that end, artificial intelligence and machine learning techniques have been studied as a stability prediction tool. Topology changes and data...

Ancillary services offered by renewable energy sources frequently requires the capability of bidirectional power flow and power reserve, so an energy storage system (ESS) is a solution for this requirement. A large variety of ESS solutions are in the market, and frequently are mixed to optimize the global performance. This paper presents the integr...

Transient instability is considered the most severe form of instability in power systems with grave socioeconomic repercussions if not prevented. Conventional methods, such as time domain simulations and direct methods impose limitations to fast on-line transient stability assessment in modern power systems. The development of phasor measurement un...

This paper presents the three-phase Custom Power Active Transformer (CPAT), characterized by the integration of power electronics in a transformer to facilitate grid services. Such integration enables step-up/step-down transformation between primary and secondary as well as shunt and series compensation services to the power system through a single...

Renewable Energy Source (RES)-based power plants need to control the active and reactive power at the Point of Common Connection (PCC) with the grid, in order to comply with the requirements of the Transmission System Operators (TSOs). This point is normally far away from the power converter station, and the cables and step-up transformers have a n...

Reusing electric vehicle batteries once they have been retired from the automotive application is stated as one of the possible solutions to reduce electric vehicle costs. Many publications in literature have analysed the economic viability of such a solution, and some car manufacturers have recently started running several projects to demonstrate...

At the present time distributed generation systems are required to disconnect from the main grid when there is an outage. In order to fulfill this requirement photovoltaic power plants (PV) are equipped with anti-islanding algorithms, embedded in the converters controller, to avoid the island operation. However, the current trends in the developmen...

The employment of renewable energy systems (RES) such as wind energy systems and photovoltaic (PV) systems is increasing in electrical networks. The integration of these RESs and the other types of distributed generations (DGs) has introduced new opportunities and challenges in conventional distribution networks. Most renewable energy-based DGs are...

The safe operation of grid connected power converters during abnormal condition is a key issue in order to guarantee its operation and to avoid undesired trips. In this paper different control strategies for the operation of a D-STATCOM are introduced, where the reference currents are determined in such a way that not only none of the phase current...

Grid-connected power converters, which are frequently used to link renewable generation plants with the grid, are required to provide a better functionality for large scale integration of renewables. They are expected to be grid-friendly, or even grid-supportive, instead of simply grid-feeding or grid-demanding. This paper designs a synchronous pow...