Apel Mahmud

Renewable Energy Integration: Challenges and Solutions

Green Energy and Technology: Choosing Among Alternatives.- Grid Codes: Goals and Challenges.- Fault-Ride Through criteria development.- High Penetration of Rooftop Photovoltaic Cells in Low Voltage Distribution Networks: Voltage Imbalance and Improvement.- Performance Evaluation of Grid-Connected Solar Photovoltaic (SPV) System with Different MPPT Controllers.- Optimal Siting and Sizing of Wind Turbines based on Genetic Algorithm and Optimal Power Flow.- Power Flow Analysis and Reactive Power Compensation of Grid Connected Wind Energy Conversion Systems.- Contribution of Variable-Speed Wind Generators to Frequency Regulation and Oscillation Damping in the United States Eastern Interconnection (EI).- Power Management of Low or Medium Voltage Networks with High Density of Renewable Generation.- Integration of Green Energy into Power Distribution Systems - Study of Impacts and Development of Control Methodology.- Integrating Smart PHEVs in Future Smart Grid.- Coordinating Distributed Energy Sources during Microgrid Emergency Operation.- A Novel Aggregation Technique using Mechanical Torque Compensating Factors for DFIG Wind Farms.- DC Grid Interconnection for Conversion Losses and Cost Optimization.- Interconnected Autonomous Microgrids in Smart Grids with Self-Healing capability.- Agent-based Smart Grid Protection and Security.- Vulnerabilities of Smart Grid State Estimation against False Data Injection Attack.- Impediments and Model for Network Centrality Analysis of a Renewable Integrated Electricity Grid.

Multi-Agent Approach for Enhancing Security of Protection Schemes in Cyber-Physical Energy Systems

This paper presents a distributed multiagent scheme to detect and identify cyber threats on the protection systems of power grids. The integration of information and communication technologies into existing power grids builds critical cyber-physical energy systems, in which digital relays are networked cyber-physical components subject to various cyber threats. Cyber attacks on protection systems may mimic real faults, cause component failure, and disable the communication links. Agents utilize both cyber and physical properties to reinforce the detection technique and further distinguish cyber attacks from physical faults. This paper also introduces the problem of secure communication protocols and highlights the comparative studies for enhancing the security of the protection systems. The proposed scheme is validated using a benchmark power system under various fault and cyber attack scenarios.

Enhancement of transient stability limit and voltage regulation with dynamic loads using robust excitation control

Abstract In stressed power systems with large induction machine component, there exist undamped electromechanical modes and unstable monotonic voltage modes. This article proposes a sequential design of an excitation controller and a power system stabiliser (PSS) to stabilise the system. The operating region, with induction machines in stressed power systems, is often not captured using a linearisation around an operating point, and to alleviate this situation a robust controller is designed which guarantees stable operation in a large region of operation. A minimax linear quadratic Gaussian design is used for the design of the supplementary control to automatic voltage regulators, and a classical PSS structure is used to damp electromechanical oscillations. The novelty of this work is in proposing a method to capture the unmodelled nonlinear dynamics as uncertainty in the design of the robust controller. Tight bounds on the uncertainty are obtained using this method which enables high-performance controllers. An IEEE benchmark test system has been used to demonstrate the performance of the designed controller.

Stability enhancement of DFIG wind turbine using LQR pitch control over rated wind speed

A novel pitch control design method is proposed for the doubly fed induction generator (DFIG) wind turbine (WT) using linear quadratic regulator (LQR). A seven-order model represents the DFIG WT which is linearized by truncated Taylor series expansion. A systematic approach is adopted to determine the weighting matrices in LQR design for the optimal solution. Simulations have been carried out to compare the performance of the proposed LQR pitch control method against a PI pitch control for small and large disturbances. It is shown that the proposed control method enhances low-voltage ride-through capability and improves system damping under large disturbances.

An Enhanced Control Scheme for an IPM Synchronous Generator Based Wind Turbine With MTPA Trajectory and Maximum Power Extraction

This paper proposes an enhanced control scheme for a direct drive variable speed wind turbine with an interior permanent magnet (IPM) synchronous generator. The proposed control scheme incorporates maximum torque per ampere (MTPA) trajectory and maximum power extraction, which ensures the generation of required torque for maximum power extraction with minimum stator current. This in turn minimizes stator copper loss and excessive heat generated in the IPM synchronous generator. The performance of the proposed control scheme has been validated through rigours simulation and experimental studies under varying wind speed conditions. The simulation and experimental results demonstrate the efficacy of the proposed control method.

Interference management for cognitive radio enabled smart grid communication

In this paper, interference management for cognitive radio (CR)-enabled smart grid communication is investigated. Here multiple smart meters (SMs) communicate with the control centre simultaneously through a data concentrator unit (DCU) while co-existing with the primary user of the CR network and thus, sharing the same resources. The impact of the resulting interference between primary transmitters (PTs) and SMs is studied through the mean square error (MSE) formulations at the DCU, control centre and primary receiver (PR). Linear precoding techniques are then designed to minimize these MSEs while keeping the interferences within a pre-defined level. Moreover, the error performance of CR-enabled smart grid communication is investigated for a benchmark low voltage (LV) feeder, adopted by CIGRE (Conseil International des Grands Rseaux lectriques). The results indicate that when the PT moves away from the PR (and the DCU), the error performance at the PR degrades while the error performance at the DCU and the control centre improves. In all the cases, optimum precoders and decoders have been found to improve the error performances at the DCU, control centre and the PR.

Dynamic stability analysis of hybrid islanded DC microgrids using a nonlinear backstepping approach

This paper presents a strategy for dynamic stability analysis of hybrid islanded DC microgrids using nonlinear backstepping controllers (NBCs) with different microgrid components. The main components of the DC microgrid are a solar photovoltaic system, a diesel generator with rectifier, loads, and a battery energy storage system. In this paper, the controller is designed to control the output power of these components as well as to minimize the mismatch between the generation and consumptions while maintaining a constant DC-bus voltage where all microgrid components are directly or indirectly connected to this DC-bus through power electronic interfaces. The proposed NBC is designed recursively based on the Lyapunov theory for each component of the microgrid. The overall stability of the whole DC microgrid is analyzed through the formulation of control Lyapunov functions (CLFs) during the different stages of the design process and the theoretical stability is ensured through the negative semidefiniteness of the derivative of CLFs. The effectiveness of the proposed controller is evaluated on a hybrid DC microgrid under different operating conditions and compared with a nonlinear sliding mode controller (SMC). Simulation results demonstrate the superiority of the proposed control scheme over the SMC in terms of achieving steady-state operating conditions.

Nonlinear Decentralized Feedback Linearizing Controller Design for Islanded DC Microgrids

Abstract This paper aims to design decentralized controllers for different components in islanded DC microgrids. The major components in the DC microgrid as considered in this paper include a fuel cell, solar photovoltaic (PV) unit, and battery energy storage system (BESS) along with critical and non-critical loads. The main control objective is to maintain the power balance within the DC microgrid through the regulation of the common DC-bus voltage. The controllers are designed based on the dynamical models of the fuel cell, solar PV unit, and BESS. The feedback linearization technique is employed to obtain the control laws, which simplifies the original dynamical models and decouples different components in the form of several subsystems. In this way, the feedback linearization technique allows different components in DC microgrids to achieve the desired control objectives by using only the local information (i.e., in a decentralized manner). The performance of the proposed decentralized controllers for different components is evaluated on a test DC microgrid under different operating conditions. Simulation results demonstrate that the proposed control scheme performs in a much better way as compared to an existing proportional integral controller.

Nonlinear Adaptive Backstepping Controller Design for Three-Phase Grid-Connected Solar Photovoltaic Systems

Abstract A cascaded control structure is proposed in this paper for injecting active and reactive power in a three-phase grid-connected solar photovoltaic (PV) system by considering external disturbances. In the proposed cascaded control structure, there are two control loops—the outer loop voltage controller is used to ensure a continuous balance in power flow between the PV arrays and electrical power grid whereas the inner loop current controller controls the output current of the inverter. Moreover, the DC-DC boost converter is controlled to achieve a constant voltage at the input of the inverter. In order to obtain the power balance and extract maximum power, an incremental conductance (IC) based maximum power point tracking (MPPT) method is used in this paper. The current controller is designed using a nonlinear adaptive backstepping technique to regulate the active and reactive components of the grid current. The regulation of these currents towards desired values which in turn control the active and reactive power delivered into the grid. The overall stability analysis of the system is performed based on the formulation of control Lyapunov functions (CLFs). Finally, the performance of the designed controller is tested on three-phase grid-connected PV systems with single as well as multiple PV units under different environmental conditions and compared with an existing sliding mode controller. Simulation results confirm the effectiveness of the proposed adaptive backstepping control scheme and demonstrate the superior performance over the sliding mode controller.