• Energy Research

With the proliferation of large-scale grid-connected wind farms, subsynchronous oscillation (SSO) incidents associated with Type-4 wind turbines (WTs) with a permanent magnet synchronous generator (PMSG) have occurred frequently. These incidents have caused severe reliability risks to the power grid. Conventionally, P-Q capability charts are utilized to ensure the safety operating region of a synchronous generator. However, a PMSG WT exhibits completely different and dynamic P-Q capability characteristics due to the difference in energy conversion technique and several critical factors related to the WT power converters. This paper presents a comprehensive dynamic P-Q capability study of a PMSG WT with sufficient and accurate considerations of the WT control and operation in the dq reference frame, its power converter constraints, and grid dynamics. Models of a PMSG WT are first developed based on its control principle in the dq reference frame. Then, algorithms for obtaining the P-Q capability charts of the WT are developed with the considerations of complete WT constraints in different aspects. The study analyzes the root cause of many abnormal operations of grid-connected PMSG WTs, reported in the literature, from the dynamic P-Q capability perspectives. The proposed study is verified via an electromagnetic transient (EMT) model of a grid-connected Type-4 WT.

Fairness is now a significant issue in demand response because of its importance in customer attraction. Studies have shown that current demand response programs are lacking fairness considerations so that this may prevent demand response program penetration. In this article, fairness will be discussed and explored in terms of fair delay of energy usage instead of the existing fair bill approach. A mathematical formation of the system is provided and an algorithm is proposed, including back-off, carry-on, and optimization procedures. In order to find the best policy for using this algorithm, simulations are conducted to find the best policy in order to lower all the customers’ total cost while bounding the customers’ delays within a fairness range. The simulation results show the best policy under two different simulation setups. Moreover, the energy consumption scheduling algorithm with the fair delay control has much better fair delay index performance than the energy consumption scheduling algorithm without fair delay control, with 20%–65% improvement, depending on the environments.

With the increasing integration of renewable and sustainable energy in microgrids, the prediction errors of these energy resources may degrade the economic efficiency of a microgrid because there is a time-scale gap between the large time-scale economic dispatch and the small time-scale frequency restoration control. In this paper, a distributed event-triggered secondary control method is proposed to deal with the economic dispatch and frequency restoration control for droop-controlled AC microgrids. The proposed control strategy can ensure economic dispatch and frequency restoration control at the same time, which reduces the operation cost of AC microgrids by bridging the time-scale gap between them. Furthermore, a simple event-triggered condition is designed to implement the proposed event-triggered secondary control, which only requires the communication between the neighboring agents when a significant change of state in the microgrid occurs, which is easy to implement and can reduce the communication burden.

Microgrids (MGs) are presented as a cornerstone of smart grid, which can integrate renewable energy sources environmentally, friendly, and reliably. Hierarchical control strategies, i.e. primary droop control, second automatic generation control (AGC), and tertiary economic dispatch (ED), are widely used to control and optimise an MG. However, the gap between large time‐scale ED and small time‐scale AGC may decrease the economical efficiency of an MG. To address this problem, this study proposes a distributed economic AGC (EAGC) algorithm. The algorithm is fully distributed, as each distributed generator is assigned with an agent and the agents only require the local measurements and communication with its neighbours. Compared with centralised algorithms, the distributed control algorithm is easy to fulfil the plug‐and‐play requirements and reduces costs to modify the architecture of an MG. Furthermore, the proposed EAGC algorithm is suitable for all possible operation modes of an MG, i.e. islanded mode, grid‐connected mode, and transition mode. To improve the robustness against agent loss or communication link fault, the topology of agents’ communication network is designed to satisfy the N − 1 rule. The effectiveness of the proposed algorithm is demonstrated through the simulation tests which involve plenty of case studies.

With the increasing integration of PV generation in AC microgrids, it is challenging to keep the stability of system frequency due to the intermittent and stochastic nature of PVs. Thus, in order to reduce the investment and maintenance costs of storage systems, the electric utility has shown increasing interest in calling on PVs to provide frequency regulation services. In this paper, a novel sliding mode control (SMC) based adaptive power point tracking (APPT) control strategy is proposed to provide bi-directional primary frequency regulation (BPFR) of an AC microgrid. In this strategy, in order to restrain the variation of frequency, the sliding mode surface is adaptively regulated to provide an adaptive power reserve. Thus, the PVs will have a power headroom to regulate the frequency both up and down through releasing the reserved power or increasing the reserves of the PV systems. Furthermore, the sliding mode surface is adaptively regulated only based on the locally measured frequency of the microgrid without the requirements of communication, detailed PV model, irradiance sensors as well as MPP estimators. Thus, the proposed control strategy shows the advantages of easy to implement and reduces the investment and maintenance costs of installing storage systems or irradiance sensors.

Residential solar photovoltaic (PV) energy is becoming an increasingly important part of the world's renewable energy. A residential solar PV array is usually connected to the distribution grid through a single-phase inverter. Control of the single-phase PV system should maximize the power output from the PV array while ensuring overall system performance, safety, reliability, and controllability for interface with the electricity grid. This paper has two main objectives. The first objective is to develop an artificial neural network (ANN) vector control strategy for an LCL -filter based single-phase solar inverter. The ANN controller is trained to implement optimal control, based on approximate dynamic programming. The second objective is to evaluate the performance of the ANN-based solar PV system by simulating the PV system behavior for grid integration and maximum power extraction from solar PV array in a realistic residential PV application and building an experimental solar PV system for hardware validation. The results demonstrate that a residential PV system using the ANN control outperforms the PV system using the conventional standard vector control method and proportional resonant control method in both simulation and hardware implementation. This is also true in the presence of noise, disturbance, distortion, and nonideal conditions.

Une pile à combustible (FC) est l'une des solutions les plus viables à la crise énergétique actuelle et au problème de pollution de l'environnement. Il peut être appliqué dans la production d'énergie, l'alimentation électrique portable, ainsi que dans les véhicules hybrides. En raison de la nature polyvalente de cette source d'énergie et de la non-dépendance aux conditions environnementales, les FC peuvent être une source importante de source d'énergie alternative à l'avenir. Les chercheurs travaillent sur les topologies de conversion de puissance et le développement de stratégies de contrôle pour les applications FC au cours de la dernière décennie. Cependant, le dernier résumé des progrès dans ce secteur n'est pas disponible dans la littérature. Cet article vise à discuter des différentes techniques de contrôle et des systèmes de gestion de l'énergie rapportés dans la littérature. Les configurations sont classées en fonction de leur nature, de leur domaine d'application et de leurs performances. Différentes stratégies de gestion de l'énergie utilisées dans les systèmes à base de piles à combustible sont considérées ici pour l'analyse qualitative. Les caractéristiques essentielles telles que les avantages, les inconvénients et les possibilités d'amélioration des diverses stratégies de gestion de l'énergie des véhicules à pile à combustible sont discutées du point de vue du système de contrôle. Enfin, les tendances récentes dans le développement de systèmes hybrides de gestion de l'énergie à pile à combustible sont présentées pour améliorer les performances sur la base de l'analyse qualitative ci-dessus. Cet article aidera les chercheurs dans ce domaine à connaître l'état actuel, les tendances futures et les futures orientations de la recherche sur les piles à combustible pour la production d'électricité. Una pila de combustible (FC) es una de las soluciones más viables a la crisis energética actual y al problema de la contaminación ambiental. Se puede aplicar en generación de energía, fuente de alimentación portátil, así como en vehículos híbridos. Debido a la naturaleza versátil de esta fuente de energía y a la no dependencia de las condiciones ambientales, las FC pueden ser una fuente importante de energía alternativa en el futuro. Los investigadores están trabajando en topologías de conversión de potencia y desarrollo de estrategias de control para la aplicación de FC durante la última década. Sin embargo, el último resumen de los avances en este sector no está disponible en la literatura. Este artículo tiene como objetivo discutir las diversas técnicas de control y sistemas de gestión de energía reportados en la literatura. Las configuraciones se clasifican según su naturaleza, área de aplicación y rendimiento. Las diferentes estrategias de gestión de la energía utilizadas en los sistemas basados en pilas de combustible se consideran aquí para el análisis cualitativo. Las características esenciales, como las ventajas, desventajas y oportunidades de mejora de diversas estrategias de gestión energética de los vehículos de pila de combustible, se discuten desde el punto de vista del sistema de control. Finalmente, se presentan las tendencias recientes en el desarrollo de sistemas de gestión de energía híbridos de pila de combustible para mejorar el rendimiento en función del análisis cualitativo anterior. Este artículo ayudará a los investigadores en este campo a conocer el estado actual, la tendencia futura y las futuras direcciones de investigación en la investigación de celdas de combustible para la generación de energía. A fuel cell (FC) is one of the most viable solutions to the current energy crisis and environmental pollution problem. It can be applied in power generation, portable power supply, as well as in hybrid vehicles. Due to the versatile nature of this energy source and non-dependency over the environmental conditions, FCs can be a significant source of alternative energy source in the future. Researchers are working on power conversion topologies and control strategies development for FC application for the past decade. However, the latest summary of the progress in this sector is not available in the literature. This article is aimed at discussing the various control techniques and energy management systems reported in the literature. The configurations are categorized according to their nature, application area, and performance. Different energy management strategies used in fuel cell-based systems are considered here for the qualitative analysis. The essential characteristics such as the advantages, disadvantages, and improvement opportunities of various energy management strategies of fuel cell vehicles are discussed from the control system point of view. Finally, the recent trends in the development of fuel cell hybrid energy management systems are presented to improve the performance based on the above qualitative analysis. This article will help the researchers in this field to know the current status, future trend and the future research directions in fuel cell research for power generation. خلية الوقود (FC) هي واحدة من أكثر الحلول قابلية للتطبيق لأزمة الطاقة الحالية ومشكلة التلوث البيئي. يمكن استخدامه في توليد الطاقة، وإمدادات الطاقة المحمولة، وكذلك في المركبات الهجينة. نظرًا للطبيعة المتنوعة لمصدر الطاقة هذا وعدم الاعتماد على الظروف البيئية، يمكن أن تكون FCs مصدرًا مهمًا لمصدر الطاقة البديلة في المستقبل. يعمل الباحثون على طوبولوجيا تحويل الطاقة وتطوير استراتيجيات التحكم لتطبيق FC على مدى العقد الماضي. ومع ذلك، فإن أحدث ملخص للتقدم المحرز في هذا القطاع غير متوفر في الأدبيات. تهدف هذه المقالة إلى مناقشة تقنيات التحكم المختلفة وأنظمة إدارة الطاقة الواردة في الأدبيات. يتم تصنيف التكوينات وفقًا لطبيعتها ومنطقة التطبيق والأداء. يتم النظر هنا في استراتيجيات إدارة الطاقة المختلفة المستخدمة في الأنظمة القائمة على خلايا الوقود للتحليل النوعي. تتم مناقشة الخصائص الأساسية مثل مزايا وعيوب وفرص التحسين لاستراتيجيات إدارة الطاقة المختلفة لمركبات خلايا الوقود من وجهة نظر نظام التحكم. أخيرًا، يتم عرض الاتجاهات الحديثة في تطوير أنظمة إدارة الطاقة الهجينة لخلايا الوقود لتحسين الأداء بناءً على التحليل النوعي أعلاه. ستساعد هذه المقالة الباحثين في هذا المجال على معرفة الوضع الحالي والاتجاه المستقبلي واتجاهات البحث المستقبلية في أبحاث خلايا الوقود لتوليد الطاقة.

In this paper, a fully distributed hierarchical control strategy is proposed for operating networked grid-supporting inverters (GSIs) in islanded ac microgrids (MGs). The primary control level implements frequency and voltage control of an ac MG through a cascaded structure, consisting of a droop control loop, a virtual impedance control loop, a mixed ${H_2}/{H_\infty }$ -based voltage control loop, and a sliding-mode-control-based current loop. Compared to conventional proportional-plus-integral-based cascaded control, the proposed cascaded control does not require a precise model for the GSI system. The proposed secondary control level implements distributed-consensus-based economic automatic generation control and distributed automatic voltage control, which integrates the conventional secondary control and tertiary control into a single control level by bridging a gap between traditional secondary control and tertiary control. Simulation results demonstrate the effectiveness of the proposed hierarchical control strategy.

A microgrid (MG) with integrated renewable energy resources can benefit both utility companies and customers. As a result, they are attracting a great deal of attention. The control of a MG is very important for the stable operation of a MG. The droop-control method is popular since it avoids circulating currents among the converters without using any critical communication between them. Traditional droop control methods have the drawback of an inherent trade-off between power sharing and voltage and frequency regulation. An adaptive droop control method is proposed, which can operate in both the island mode and the grid-connected mode. It can also ensure smooth switching between these two modes. Furthermore, the voltage and frequency of a MG can be restored by using the proposed droop controller. Meanwhile, the active power can be dispatched appropriately in both operating modes based on the capacity or running cost of the Distributed Generators (DGs). The global information (such as the average voltage and output active power of the MG and so on) required by the proposed droop control method to restore the voltage and frequency deviations can be acquired distributedly based on the Multi Agent System (MAS). Simulation studies in PSCAD demonstrate the effectiveness of the proposed control method.