Khalid Abdullah Khan

Bio: Khalid Abdullah Khan is an academic researcher from King Fahd University of Petroleum and Minerals. The author has contributed to research in topics: Photovoltaic system & AC power. The author has an hindex of 3, co-authored 10 publications receiving 24 citations.

Improving the Transient Response of Hybrid Energy Storage System for Voltage Stability in DC Microgrids Using an Autonomous Control Strategy

Abstract: In renewable microgrid systems, energy storage system (ESS) plays an important role, as an energy buffer, to stabilize the system by compensating the demand-generation mismatch. Battery energy storage system serves as a decisive and critical component. However, due to low power density and consequently slow dynamic response the lifetime of BESS is observably reduced due to high current stress, specifically experienced during abrupt/transient power variations. Hence, hybridization with supercapacitor storage system is conferred. Additionally, the controllers designed for energy storage systems should substantially respond for compensating the transient requirement of the system. In this article, we propose a decoupled control strategy for batteries and supercapacitors based on k - Type compensators and a nonlinear PI controller (NPIC) respectively. The formulated control design is tested for voltage regulation in a standalone microgrid. Furthermore, a comparative analysis is presented with benchmark low-pass-filter (LPF) based controller. The results obtained shows the proposed control technique possess a faster response with improved voltage regulation capabilities. For the test system regulated at 48 V for various abrupt load-generation various case studies presented, the proposed methodology maintains a significantly reduced voltage deviation between 47 V - 51 V in contrast to 45 V - 56 V observed in the LPF methodology. Furthermore, the complexity is simpler in comparison to LPF based control strategy and a comparative obviation of additional sensing devices is achieved, that inherently reduces the detrimental effect on ESS response during transient condition.

Hybrid Energy Storage System for Voltage Stability in a DC Microgrid Using a Modified Control Strategy

Abstract: In renewable based DC microgrids, energy storage devices are implemented to compensate for the generation-load power mismatch. Usually, Battery Energy Storage Systems (BESS) are used, but they cannot meet the transient load demand due to low power density leading to voltage fluctuations. For this reason, Supercapacitor Storage Systems (SCSS) are used. In this respect the controller used for regulating the power electronic interface must respond quickly to feed the power from SCSS to the grid. In this paper, a decoupled controller for both BESS and SCSS are designed based on k-type compensators and Lagrange Interpolation (LI) based controllers are designed for BESS and SCSS controllers respectively. As compared to conventional control strategies based on LPF/HPF – PI based controllers, the proposed control strategy possesses a faster response and ensures a reduced voltage fluctuation. Furthermore, the need for converter voltage and current sensing device is reduced and with the obviation of the LPF/HPF filters the complexity and processing time of the converter is reduced.

Robust Control for Optimized Islanded and Grid-Connected Operation of Solar/Wind/Battery Hybrid Energy

Abstract: Wind and solar energy systems are among the most promising renewable energy technologies for electric power generations. Hybrid renewable energy systems (HRES) enable the incorporation of more than one renewable technology, allowing increased reliability and efficiency. Nevertheless, the introduction of variable generation sources in concurrence with the existing system load demand necessitates maintaining the power balance between the components of the HRES. Additionally, the efficiency of the hybrid power supply system is drastically affected by the number of converters interfacing its components. Therefore, to improve the performance of the HRES, this paper proposes a robust sliding mode control strategy for both standalone and grid-connected operation. The control strategy achieves maximum power point tracking for both the renewable energy sources and stabilizes the DC-bus and load voltages irrespective of the disturbances, change in load demand, variations of irradiance level, temperature, and wind speed ensuring an efficient energy management. Furthermore, the solar PV system is directly linked to the DC-bus obviating the need for redundant interfacing boost converters with decreased costs and reduced system losses. Lyapunov candidate function is used to prove the asymptotic stability and the convergence of the entire system. The robustness of the proposed control strategy is tested and validated under various conditions of HRES, demonstrating its efficacy and performance under various conditions of the HRES.

A Reactive Power Compensation Strategy in Radial Distribution Network with High PV Penetration

Abstract: The introduction of photovoltaics (PV) based power generation has brought about the trend of residential rooftop PVs. Therefore the concept of energy market of buying and selling of power between the utility and consumers has been established. However, high penetration of PV causes congestion leading to voltage violation conditions, especially in case of grid fault that requires islanding of the PV systems. Furthermore, in case of radial distribution system (RDN), high PV penetration imposes over-voltage and under-voltage issues during peaking PV production and peak loading conditions respectively. Taking these into consideration, this paper proposes a voltage regulation methodology based on active-reactive power management through PV inverters. A PQ-V control curve is formulated for the PV inverters and corresponding tuning parameters are introduced for rapid voltage regulation using real-time measurements. The control strategy is evaluated on two scenarios of RDN based on different R/X ratios and nodes distances to validate its robustness.

Integrated Power Management and Nonlinear-Control for Hybrid Renewable Microgrid

Abstract: The introduction of variability with the integration of renewable energy sources in the generation-side of the power network degrades the power quality of the supplied power. With the increased demand of renewable energy integration in the electricity network the concept of microgrid provides significant controllability and mitigation of system variations. This paper presents a simultaneous power management and control scheme for a hybrid renewable microgrid consisting of solar PV system, permanent magnet synchronous generator (PMSG) driven by wind turbine, and battery energy storage system. The PV system is connected directly to the DC-link, thus lowering losses and cost by eliminating the redundant DC/DC boost converter. Moreover, maximum power point tracking (MPPT) algorithms are utilized to extract the maximum power from each renewable energy source. A sliding mode control technique is designed to improve the robust performance of the system and ensure efficient energy management irrespective of system disturbances, load fluctuations, transience of irradiance, and variation of wind speed. The proposed optimization framework is tested and validated on an AC microgrid system proving its efficacy.

A Comprehensive Review of Recent Advances in Smart Grids: A Sustainable Future with Renewable Energy Resources

Abstract: The smart grid is an unprecedented opportunity to shift the current energy industry into a new era of a modernized network where the power generation, transmission, and distribution are intelligently, responsively, and cooperatively managed through a bi-directional automation system. Although the domains of smart grid applications and technologies vary in functions and forms, they generally share common potentials such as intelligent energy curtailment, efficient integration of Demand Response, Distributed Renewable Generation, and Energy Storage. This paper presents a comprehensive review categorically on the recent advances and previous research developments of the smart grid paradigm over the last two decades. The main intent of the study is to provide an application-focused survey where every category and sub-category herein are thoroughly and independently investigated. The preamble of the paper highlights the concept and the structure of the smart grids. The work presented intensively and extensively reviews the recent advances on the energy data management in smart grids, pricing modalities in a modernized power grid, and the predominant components of the smart grid. The paper thoroughly enumerates the recent advances in the area of network reliability. On the other hand, the reliance on smart cities on advanced communication infrastructure promotes more concerns regarding data integrity. Therefore, the paper dedicates a sub-section to highlight the challenges and the state-of-the-art of cybersecurity. Furthermore, highlighting the emerging developments in the pricing mechanisms concludes the review.

Improving the Transient Response of Hybrid Energy Storage System for Voltage Stability in DC Microgrids Using an Autonomous Control Strategy

Abstract: In renewable microgrid systems, energy storage system (ESS) plays an important role, as an energy buffer, to stabilize the system by compensating the demand-generation mismatch. Battery energy storage system serves as a decisive and critical component. However, due to low power density and consequently slow dynamic response the lifetime of BESS is observably reduced due to high current stress, specifically experienced during abrupt/transient power variations. Hence, hybridization with supercapacitor storage system is conferred. Additionally, the controllers designed for energy storage systems should substantially respond for compensating the transient requirement of the system. In this article, we propose a decoupled control strategy for batteries and supercapacitors based on k - Type compensators and a nonlinear PI controller (NPIC) respectively. The formulated control design is tested for voltage regulation in a standalone microgrid. Furthermore, a comparative analysis is presented with benchmark low-pass-filter (LPF) based controller. The results obtained shows the proposed control technique possess a faster response with improved voltage regulation capabilities. For the test system regulated at 48 V for various abrupt load-generation various case studies presented, the proposed methodology maintains a significantly reduced voltage deviation between 47 V - 51 V in contrast to 45 V - 56 V observed in the LPF methodology. Furthermore, the complexity is simpler in comparison to LPF based control strategy and a comparative obviation of additional sensing devices is achieved, that inherently reduces the detrimental effect on ESS response during transient condition.

Multi-Input Nonlinear Programming Based Deterministic Optimization Framework for Evaluating Microgrids with Optimal Renewable-Storage Energy Mix

Abstract: Integration of renewable energy sources (RES) in a distribution network facilities the establishment of sustainable power systems. Concurrently, the incorporation of energy storage system (ESS) plays a pivotal role to maintain the economical significance as well as mitigates the technical liabilities associated with uncontrollable and fluctuating renewable output power. Nevertheless, ESS technologies require additional investments that imposes a techno-economic challenge of selection, allocation and sizing to ensure a reliable power system that is operationally optimized with reduced cost. In this paper, a deterministic cost-optimization framework is presented based on a multi-input nonlinear programming to optimally solve the sizing and allocation problem. The optimization is performed to obviate the demand-generation mismatch, that is violated with the introduction of variable renewable energy sources. The proposed optimization method is tested and validated on an IEEE 24-bus network integrated with solar and wind energy sources. The deterministic approach is solved using GAMS optimization software considering the system data of one year. Based on the optimization framework, the study also presents various different scenarios of renewable energy mix in combination with advanced ESS technologies to outline an technical as well as economical framework for ESS sizing, allocation, and selection. Based on the optimal results obtained, the optimal sizing and allocation were obtained for lead-acid, lithium-ion, nickel-cadmium and sodium-sulfur (NaS) battery energy storage system. While all these storage technologies mitigated the demand-generation mismatch with optimal size and location. However, the NaS storage technology was found to be the best among the given storage technologies for the given system minimum possible cost. Furthermore, it was observed that the cost of hybrid wind-solar mix system results in the lowest overall cost.

Techno-Economic Assessment and Operational Planning of Wind-Battery Distributed Renewable Generation System

Abstract: Electrical energy and power demand will experience exponential increase with the rise of the global population. Power demand is predictable and can be estimated based on population and available historical data. However, renewable energy sources (RES) are intermittent, unpredictable, and environment-dependent. Interestingly, microgrids are becoming smarter but require adequate and an appropriate energy storage system (ESS) to support their smooth and optimal operation. The deep discharge caused by the charging–discharging operation of the ESS affects its state of health, depth of discharge (DOD), and life cycle, and inadvertently reduces its lifetime. Additionally, these parameters of the ESS are directly affected by the varying demand and intermittency of RES. This study presents an assessment of battery energy storage in wind-penetrated microgrids considering the DOD of the ESS. The study investigates two scenarios: a standalone microgrid, and a grid-connected microgrid. The problem is formulated based on the operation cost of the microgrid considering the DOD and the lifetime of the battery. The optimization problem is solved using non-linear programming. The scheduled operation cost of the microgrid, the daily scheduling cost of ESS, the power dispatch by distributed generators, and the DOD of the battery storage at any point in time are reported. Performance analysis showed that a power loss probability of less than 10% is achievable in all scenarios, demonstrating the effectiveness of the study.

Robust Control for Optimized Islanded and Grid-Connected Operation of Solar/Wind/Battery Hybrid Energy

Abstract: Wind and solar energy systems are among the most promising renewable energy technologies for electric power generations. Hybrid renewable energy systems (HRES) enable the incorporation of more than one renewable technology, allowing increased reliability and efficiency. Nevertheless, the introduction of variable generation sources in concurrence with the existing system load demand necessitates maintaining the power balance between the components of the HRES. Additionally, the efficiency of the hybrid power supply system is drastically affected by the number of converters interfacing its components. Therefore, to improve the performance of the HRES, this paper proposes a robust sliding mode control strategy for both standalone and grid-connected operation. The control strategy achieves maximum power point tracking for both the renewable energy sources and stabilizes the DC-bus and load voltages irrespective of the disturbances, change in load demand, variations of irradiance level, temperature, and wind speed ensuring an efficient energy management. Furthermore, the solar PV system is directly linked to the DC-bus obviating the need for redundant interfacing boost converters with decreased costs and reduced system losses. Lyapunov candidate function is used to prove the asymptotic stability and the convergence of the entire system. The robustness of the proposed control strategy is tested and validated under various conditions of HRES, demonstrating its efficacy and performance under various conditions of the HRES.