Enrique Espina González

University of Santiago, Chile | USACH · Departamento de Ingeniería Eléctrica

Hybrid AC/DC microgrids (H-MGs) are a prominent solution for integrating distributed generation and modern AC and DC loads. However, controlling these systems is challenging as multiple electrical variables need to be controlled and coordinated. To provide flexibility to the control system, these variables can be regulated to specific values or wit...

The rated power of wind turbines has consistently enlarged as large installations can reduce energy production costs. Multi-megawatt wind turbines are frequently used in offshore and onshore facilities, and today is possible to find wind turbines rated over 15 MW. New developments in generators and power converters for multi-MW wind turbines are ne...

Modular Multilevel Converters are considered one of the most suitable technologies for High-Voltage Direct Current transmission. However, they have been recently proposed in additional applications such as electric vehicle charging, Solid-State Transformers, and motor drives. In this context, this paper presents the modeling and control of a Modula...

This paper presents a novel scheme based on distributed model-based predictive control for the secondary level control of hybrid AC/DC microgrids. Prediction models based on droop control and power transfer equations are proposed to characterize the generators in both the AC and DC sub-microgrids, whereas power balance constraints are used to predi...

In three-phase unbalanced systems, where the circulation of zero sequence current is necessary, four-leg converters provide a neutral connection for single-phase or other unbalanced loads typically utilized in three-phase distribution systems. In addition, control of the magnitude and phase of the zero-sequence voltage and/or current are also achie...

Direct Current Microgrids seems to be a better alternative in perspective of different advantages over AC microgrids, a better performance and reduce power conversions and different operations mode and power transference among different units that needs DC (electric vehicles, Photovoltaic cells),however different internal control units may affect t...

This paper proposes a cooperative control scheme for power quality compensation, exploiting the remaining capacity of power electronics converters typically used in microgrids for active power supply. Consensus terms are proposed to mitigate imbalances and harmonics in a mining-industry microgrid. In contrast to the classical approach, cooperative...

Secondary control strategies in hybrid ac/dc-microgrids have been conventionally designed independently for each side of the microgrid, neglecting the interaction between the ac and dc sides due to the power transferred through the interlinking converter. This has a negative effect on the power-sharing and dynamic response of the system. In this pa...

There is an increasing interest and research effort focused on the analysis, design and implementation of distributed control systems for AC , DC and hybrid AC / DC microgrids. It is claimed that distributed controllers have several advantages over centralised control schemes, e.g., improved reliability, flexibility, controllability, black...

A distributed control strategy is proposed to share unbalanced currents in three-phase three-wire isolated AC Microgrids (MGs). It is based on a novel approach where, rather than analysing the MG as a three-phase system, it is analysed as three single-phase subsystems. The proposal uses a modified single-phase Q-E droop scheme where two additional...

This paper describes a flexible testbed of a hybrid AC/DC microgrid developed for research purposes. The experimental setup is composed of 3 AC and 6 DC distributed generator units, which are emulated by using three-legs inverters and settable output filters. The microgrid architecture allows validating control schemes upstream of the modulation st...

In this paper, two predictive modulation schemes are derived for a hybrid modular multilevel converter. The modulation scheme considers the electric model of both full and half bridge cells to predict the capacitor voltages in the next sampling period. The performance of both modulators is assessed through simulations and experimental results for d...

In this paper, a distributed secondary control strategy for hybrid ac/dc-microgrids is proposed. The control strategy restores the variables modified by the primary control loop, i.e. voltage on the dc-side and voltage amplitude and frequency of the ac-side, to their nominal values while maintaining a good power-sharing capability between ac-and dc...

Collaborative control of power converters operating in microgrids with unbalanced single-phase loads is difficult to achieve, considering that the voltages and currents have positive-, negative-, and zero-sequence components. In this paper, a new control scheme for collaborative control of four-leg microgrids is proposed. The main advantage of the...

In this work, a methodology for the design and implementation of a microgrid for supplying electricity to indigenous Mapuche communities in Chile is proposed. The challenge in designing this microgrid lies in making it compatible with a community’s socio-cultural situation, thereby allowing active community participation in all stages of project de...

Modular Multilevel Converters (MMC) are considered an attractive solution for high-power medium-voltage drives. However, in drive applications, the influence of the loading conditions leads to more complex control systems than the required ones for constant frequency applications. To solve this issue, a novel control methodology for the MMC-based d...

The Modular Multilevel Converter (MMC) is a promising topology for high power drive applications. However , large voltage fluctuations are produced in the floating capacitors when the machine is operating with high stator currents at low rotational speed. To compensate these oscillations , relatively large mitigation currents are required to keep t...

The Modular Multilevel Converter has emerged as a suitable topology for high power drive applications. However, high voltage fluctuations could appear in the converter capacitors depending on the operating drive point. Then, mitigating signals, which lead to oversized dimensioning, are required to keep the capacitor voltages within an acceptable ra...

Most low voltage microgrids have four wires and operate mainly unbalanced. To solve the associated problems to the unbalanced operation (e.g. high neutral current), this paper considers a new droop control per phase of a four-wire microgrid. Unlike to the conventional approaches, in this work, the active power per phase of each converter is shared...

El Sistema Micro-red/SMART-Farm basado en un " Modelo Participativo de Innovación Tecnológica para el Desarrollo Local " es una propuesta de innovación tecnológica con una visión social, capaz de fortalecer y consolidar el desarrollo productivo local de una comunidad rural a través de tecnologías de comunicaciones y del abastecimiento energético me...

Modular Multilevel Converters (M2C) are considered an attractive solution for high power drives. However , its operation at low rotational speeds can produce undesired voltage fluctuations in the M2C capacitors. In this paper, two methodologies to improve the converter performance in this speed range are analysed and tested. The first strategy prop...

This paper considers the control of a seven-leg back-to-back voltage source inverter arrangement, feeding a four-wire load from a three-phase permanent-magnet synchronous generator (PMSG) operating at variable speed. The PMSG is controlled using a sensorless model reference adaptive system to obtain the rotor position angle. The seven-leg converter...

This paper considers the control of a 7-leg back-to-back Voltage Source Inverter (VSI) arrangement feeding a 4-wire load from a 3-phase Permanent Magnet Synchronous Generator (PMSG) operating at variable speed. The 7-leg converter is regulated using Resonant Controllers (RCs) at the load side and self-tuning resonant controllers at the generator si...