Mohamed Moustafa

Utility-connected microgrids (MGs) provide ancillary services using distributed energy resources (DERs). However, existing DER control strategies are complex and may not yield reliable results under diverse MG configurations. To address this challenge, this paper presents a unified secondary control strategy for effective real and reactive power regulation of dispatchable energy sources. These configurations are simulated based on the practical setup of the industry-grade MG at the Center for Microgrid Research (CMR). Real and reactive power regulation strategies based on a unified proportional-integral-derivative (PID) scheme across DERs are developed and evaluated for providing secondary control at the point of common coupling (PCC). Proportional power sharing algorithms for the DERs are implemented within the PCC control, incorporating the constraints of variable renewable energy such as solar photovoltaic (PV) arrays. The proposed strategies are assessed using time-domain simulations for multiple source configurations in the real-time simulator.

Grid-forming (GFM) inverters typically employ droop-based primary control, which necessitates the implementation of robust secondary control to maintain nominal frequency and voltage, especially under dynamic conditions. While Microgrid secondary control research has primarily focused on simulation studies, practical implementation on industry-grade controllers remains a critical gap. This paper bridges the gap between theoretical and practical implementation by proposing an automation-based approach for enhanced secondary voltage and frequency regulation in GFM inverters. In this approach, secondary control architecture is simulated based on an industry-employed real-time automation controller (RTAC) architecture. RTAC parameters are optimized using a grid search optimization technique. It employs iterative random gain sampling to minimize the step response parameters. The developed controller is validated in real-time using RTAC-in-the-loop. The simulation and hardware experimental results are validated in the Center of Microgrid Research (CMR). The results confirm that the proposed method can be effectively used to replicate the industry-grade controller performance.

Addition of distributed energy resources (DERs) in power systems (PS) coupled with uncertain loading has increased system uncertainties. The usual deterministic stability solution is no longer sufficient. While probabilistic methods (PM) have been explored before, their focus has mainly been on system events like faults or the realization of microgrids composed of DERs. Voltage stability (VS) analysis of a PS mixed with DERs has not received sufficient attention. In this work, a Bayesian parameter estimation (BPE) method is proposed. BPE works efficiently with efficient sampling techniques such as the Markov Chain Monte Carlo (MCMC) to accurately estimate uncertain parameters with good computation speed while using smaller data sample sizes. DERs and loads are represented by their respective statistical models. The models are then transformed into the Bayesian inferential framework. Using the BPE algorithm, uncertain parameters are estimated and their corresponding power outputs are obtained. The estimated powers are injected in the continuous power flow (CPU) to determine the VS of the PS. The proposed BPE has been tested on the 14 generator, 59 bus Australian IEEE benchmark. Test results show that with a 4.33% generation increase from DERs, leads to 11% enhancement in voltage stability margin of the PS.

The demand to improve grid infrastructure is of utmost importance especially with the increased expansion and addition of distributed generation units to cope with today's era of transforming to smart grids. The health status of distribution transformers in an electrical grid plays a vital role in maintaining network service continuity, safety from catastrophic events, and reliability of utility operation. Monitoring transformer's health is essential for minimizing outages and extending its life in service. Various diagnostic tests and fault detection techniques have developed to effectively support utility operators in predicting failure, estimating life expectancy and condition monitor its status. For these reasons, traditional and advanced methods are required to reduce maintenance time, cost, and help in finding fault causes and location easily. This paper gives a thorough overview about widely used and latest condition monitoring techniques while highlighting strengths and limitations of each.

This paper introduces a new self-synchronization mechanism for three phase current controlled voltage source inverter (CCVSI). The grid connected operation of the inverters is smoothly managed with the use of a hybrid quasi-proportional resonant (QPR) regulator embedded with a universal droop controller. Prominently, the commonly used phase-locked-loop (PLL) that is required to for synchronization with the main grid is obviated. This way, isolation and reconnection with the main grid is achieved seamlessly without the need of a dedicated synchronization unit. Modeling and simulation results are presented using MATLAB/SIMULINK software to show the effectiveness of the proposed strategy.

Conference Title: 2017 19th European Conference on Power Electronics and Applications (EPE'17 ECCE Europe) Conference Start Date: 2017, Sept. 11 Conference End Date: 2017, Sept. 14 Conference Location: Warsaw, Poland Modular Multilevel Converter (MMC) has served as a promising Voltage Source Converter (VSC) for High Voltage Direct Current (HVDC) applications. In this paper, a new MMC Submodule (SM) topology called Modified Switched Capacitor Sub-Module (MSCSM) is proposed. The MSCSM is able to block the DC fault using the power electronics semiconductor diodes due to its intelligent configuration without the need to use circuit breakers and has reduced voltage stress across some switches. In this work, the proposed topology is analyzed along with the modified selection technique used to balance the capacitors voltages using half the number of voltage sensor. Moreover, the submodule behavior due to IGBT open-circuit failure is analyzed and a control scheme is proposed to detect such a fault and provide continuous system operation. Furthermore a comparison between the proposed MSCSM and other available submodule topologies is included to show the benefits of the proposed MSCSM. A simulation model has been developed to validate the proposed architecture and to evaluate its performance. Finally, experimental results using a three-level MMC prototype show the validity of the proposed topology.

Conference Title: 2017 19th European Conference on Power Electronics and Applications (EPE'17 ECCE Europe) Conference Start Date: 2017, Sept. 11 Conference End Date: 2017, Sept. 14 Conference Location: Warsaw, Poland This paper presents the modeling and control of a doubly-fed induction generator (DFIG) driven by a wind turbine on a real time digital simulator. Real time digital simulators are widely used in the electric power industry by utilities, equipment manufacturers and research organizations. In this paper, two scenarios are considered, the first with a detailed switching model of the back-to-back Voltage Source Converter (VSC) controlling the DFIG and the second with a simplified model of the VSC based on the concept of dynamic average-value modeling. The hardware and software tools used for the real time simulation are developed by RTDS Technologies Inc.

Conference Title: 2016 IEEE International Conference on Renewable Energy Research and Applications (ICRERA) Conference Start Date: 2016, Nov. 20 Conference End Date: 2016, Nov. 23 Conference Location: Birmingham, United Kingdom Modular multilevel converter (MMC) served as a promising converter for High Voltage Direct Current (HVDC) transmission. However, reliability is one of the most important challenges. Redundant submodules (SMs) are often used to replace the faulty SMs to ensure continuous operation of the scheme and increase the system reliability. In this paper, a fault detection and clearance is proposed for three level SMs topology without additional voltage sensors or complex algorithms. The fault is detected using a measurement technique that has half the number of voltage sensors compared to conventional half-bridge. The main advantage of the proposed technique is the reduction of the number of voltage sensors with full estimation for the capacitors voltages. Moreover, it provides fault detection and tolerance control. A simulation model has been implemented to validate the proposed technique and to evaluate its performance.

Conference Title: 2016 28th International Conference on Microelectronics (ICM) Conference Start Date: 2016, Dec. 17 Conference End Date: 2016, Dec. 20 Conference Location: Giza, Egypt This paper presents the modeling and control of a doubly-fed induction generator (DFIG) driven by a wind turbine on a real time digital simulator. Real time digital simulators are widely used in the electric power industry by utilities, equipment manufacturers and research organizations. In this paper, a real time simulation of a fully detailed model of the wind turbine and the associated power electronics including the back-to-back Voltage Source Converter (VSC) controlling the DFIG is presented. The hardware and software tools used for the real time simulation are developed by RTDS Technologies Inc.

  Conference Title: 2015 International Symposium on Smart Electric Distribution Systems and Technologies (EDST) Conference Start Date: 2015, Sept. 8 Conference End Date: 2015, Sept. 11 Conference Location: Vienna, Austria This paper describes the challenges associated with real time modeling of electrical distribution networks. Distribution networks are tightly coupled electrically which makes it more difficult to model them using parallel processing techniques. Power electronic devices and distributed energy resources are continually increasing the complexity of distribution networks and consequently the task of simulating them in real time is more difficult. Detailed and accurate models need to be made available to represent distribution loads as well as protection and control equipment. In addition, a wide variety of communication protocols with significant bandwidth are required. Finally the trend to apply Power Hardware in the Loop simulations to test distribution equipment is a challenge in of itself.