Hossein Gholizadeh Narm

This study introduces a novel strategy for mitigating false data injection (FDI) attacks within islanded DC microgrids, primarily focusing on enhancing the security of data transmission between buses. This method utilizes secondary control variables, local feedback and event‐triggered control to detect, identify and stabilize voltage during FDI attacks and ultimately eliminate the attacks. The combination of these methods results in the establishment of a resilient control. Secondary control variables, through defining a variable as a detection index (DI) and impact of FDI attacks on per‐unit current and estimated average voltage parameters, detect potential attacks. Subsequently, internal feedback ensures stability under attack conditions by increasing the gains of the local feedbacks. Moreover, the proposed event‐triggered control identifies the magnitude and location of the attack by comparing two events before and after an attack. Finally, the identified attack is mitigated by removing it from the communication link. Furthermore, after mitigating the attack, the local feedback causes the system to return to its pre‐attack state, restoring voltage regulation and current sharing to their previous levels. Simulations and experimental results demonstrate the effectiveness of the approach in stabilizing the system and mitigating various FDI attack scenarios, showcasing its potential for securing DC microgrids.

In this article, a new controller for a dc/dc buck converter is introduced, with a key feature that it does not rely on a current sensor, which minimizes sensitivity to sensor errors, including sensor noise and offsets. This is made possible by using a delayed, positive feedback term of the output voltage. The controller achieves stabilization without the need for current feedback during challenging situations of powering constant power loads and/or reverse power flow, i.e., the boost mode, operation. This article includes theoretical analyses using both approximate and precise methods, a step-by-step algorithm for designing controller parameters, and comprehensive performance evaluations through simulations and laboratory experiments, demonstrating its efficacy. This article concludes that the proposed method has robust stability and high noise immunity and is a suitable choice to be employed in extreme practical conditions.

Parallel operation of inverters is one method to increase power ratings of motor drives for high power applications. This paper proposes a novel variation of Field-Oriented Control for parallel inverters driving AC machines. The proposed strategy is implemented directly in the natural (abc) reference frame and overcomes many issues faced by conventional controllers for parallel motor drives. At the core of this control strategy is a proposed Resonant Proportional Integral (RPI) controller, which uses integrated plant dynamics to achieve the functionality of a second-order Proportional Resonant (PR) controller using only a first-order Proportional Integral (PI) controller. Hence the proposed control strategy is very simple, requiring only an inner first-order RPI controller for the the stator currents, and an outer PI controller for motor speed and maximum torque per ampere (MTPA) operation. A theoretical analysis of the RPI controller is given, which is supported by simulation and experimental results.

This article presents a controller for a dc/dc buck converter. The controller has four distinguishing features: 1) does not increase the order of the control system; 2) regulates its output voltage without a steady-state offset; 3) can have highly fast dynamics; and 4) has wide stability margins. Moreover, it can prevent and limit the transient over-current of the converter switch and protect it against possible short-circuit transient faults. The controller is based on leveraging and employing the converter's natural dynamics to address the control objectives. A similar process has been done in some recent publications. However, the proposed method of this article succeeds in completely removing any possible steady-state errors that some highly accurate applications may demand. The theoretical analysis, a clear step-by-step design algorithm for the controller parameters, and a detailed study of the proposed controller's performance using simulations and laboratory experimental results are presented in the article to illustrate its properties.

Data exchange among nodes in a distributed dc microgrid (DCMG) causes time delays that can negatively impact reliability and performance. Previous literature often assumes that local data are delayed by the same value as the transmission delay between neighboring nodes, aiming to achieve convergence of average bus voltages to the desired level. However, this assumption relies on having precise knowledge of the communication delay, which is not always feasible in real-world applications. This article presents a more realistic scenario by considering unknown and varying communication delays among links. The assumption of no self-delay for local data results in a steady-state deviation of the global average bus voltages. To address this challenge, a novel observer for average bus voltage is proposed, which significantly expands the acceptable delay range and reduces the communication burden by transmitting fewer variables through the communication links. Furthermore, a modified distributed secondary control scheme is developed, and the system model is transformed into a standard linear form represented by retarded differential equations. Stability analysis and the design of control gains for the system, considering uncertain local and public loads, are presented using the Lyapunov–Krasovskii approach. The proposed method is verified through theoretical analysis, simulation, and experimental results.

Dual Active Bridge (DAB) converters are used in DC microgrids for electric vehicle battery interfaces due to their bidirectional power transfer, high power density, and soft-switching capability. However, there are some challenges associated with these converters. On the one hand, substantial current stress and elevated RMS current can result in substantial losses and safety concerns. On the other hand, external perturbations, disturbances, and variations in load can adversely affect the performance and stability of the system. To mitigate these issues, Triple Phase-Shift (TPS) modulation strategies have been introduced to reduce peak and RMS currents, while H∞ control methods have been developed to manage system uncertainties. An important aspect of the design of H∞ control systems is the optimization of weighting function parameters, which is complicated by the complexity of the system. This work proposes a novel solution by using a revised NSGA-II algorithm for H∞ control, which facilitates the automatic determination of controller parameters efficiently with given optimization information. The proposed control method is capable of minimizing the peak or RMS current, and provide robustness against system uncertainty simultaneously. Simulation and experimental results are presented to demonstrate the robust performance and fast response times.