One of the main problems that need to be solved to allow the realisation of multi-terminal high-voltage direct current (HVDC) transmission systems is the absence of a practical power flow control method. Industry leaders and researchers have proposed a few methods of power flow control based on either the control of converter station or the connection of new power electronic equipment to the grid. This study presents the operation and control of a three-port insulated gate bipolar transistorbased current flow control (CFC) device suitable for multi-terminal HVDC systems. Key features and functionalities of the proposed controller including the balancing of cable currents, limiting the magnitude of cable current and current nulling are demonstrated. The three-port CFC was simulated using power system computer aided design (PSCAD)/electromagnetic transient and direct current (EMTDC), network simulation software to evaluate its steady state and dynamic performance. Furthermore, low-power prototypes are implemented for a two and three-ports CFC to experimentally validate their different functionalities. Simulation and experimental studies explore the fast dynamic response and the results show that the CFC studied may have a significant role to play in the control of power flows in multi-terminal high-voltage DC systems.
Optimal power flow (OPF) is considered one of the most critical challenges that can substantially impact the sustainable performance of power systems. Solving the OPF problem reduces three essential items: operation costs, transmission losses, and voltage drops. An intelligent controller is needed to adjust the power system’s control parameters to solve this problem optimally. However, many constraints must be considered that make the design process of the OPF algorithm exceedingly tricky due to the increased number of limitations and control variables. This paper proposes a multi-objective intelligent control technique based on three different meta-heuristic optimization algorithms: multi-verse optimization (MVO), grasshopper optimization (GOA), and Harris hawks optimization (HHO) to solve the OPF problem. The proposed control techniques were validated by applying them to the IEEE-30 bus system under different operating conditions through MATLAB simulations. The proposed techniques were then compared with the particle swarm optimization (PSO) algorithm, which is very popular in the literature studying how to solving the OPF problem. The obtained results show that the proposed methods are more effective in solving the OPF problem when compared to the commonly used PSO algorithm. The proposed HHO, in particular, shows that it can form a reliable candidate in solving power systems’ optimization problems.
The increasing demand for high voltage DC grids resulting from the continuous installation of offshore wind farms in the North Sea has led to the concept of multi-terminal direct current (MTDC) grids, which face some challenges. Power (current) flow control is a challenge that must be addressed to realize a reliable operation of MTDC grids. This paper presents a reduced switch count topology of a current flow controller (CFC) for power flow and current limiting applications in MTDC grids. A simple control system based on hysteresis band current control is proposed for the CFC. The theory of operation and control of the CFC are demonstrated. The key features of the proposed controller, including cable current balancing, cable current limiting, and current nulling, are illustrated. An MTDC grid is simulated using MATLAB/SIMULINK software to evaluate the steady state and dynamic performance of the proposed CFC topology. Furthermore, a low power prototype is built for a CFC to experimentally validate its performance using rapid control prototyping. Simulation and experimental studies indicate the fast dynamic response and precise results of the proposed topology. Furthermore, the proposed controller offers a real solution for power flow challenges in MTDC grids.
A microgrid is a group of distributed energy resources and interconnected loads that may be operated either in isolated mode or connected mode with the main utility within electrical boundaries. Microgrids may consist of different types of renewable energy resources such as photovoltaic panels, wind turbines, fuel cells, micro turbines, and storage units. It is highly recommended to manage the dependency on these resources by implementing an energy management unit to optimize the energy exchange so that the minimum cost is achieved. In this paper, an energy management system based on the grasshopper optimization algorithm (GOA) is proposed to determine the optimal power generated by the distributed generators in the microgrid which is required to minimize the total generation cost. The proposed unit is applied to a microgrid that consists of five generating units feeding residential, commercial, and industrial loads, and results are compared to other available research in literature to validate the proposed algorithm.
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