Integrated control and protection architecture for islanded PV-battery DC microgrids:Design, analysis and experimental verification

Direct current (dc) microgrids have gained significant interest in research due to dc generation/storage technologies—such as photovoltaics (PV) and batteries—increasing performance and reducing in cost. However, proper protection and control systems are critical in order to make dc microgrids feasible. This paper aims to propose a novel integrated control and protection scheme by using the state-dependent Riccati equation (SDRE) method for PV-battery based islanded dc microgrids. The dc microgrid under study consists of photovoltaic (PV) generation, a battery energy storage system (BESS), a capacitor bank and a dc load. The aims of this study are fast fault detection and voltage control of the dc load bus. To do so, the SDRE observer-controller—a nonlinear mathematical model—is employed to model the operation of the dc microgrid. Simulation results show that the proposed SDRE method is effective for fault detection and robust against external disturbances, resulting in it being capable of controlling the dc load bus voltage during disturbances. Finally, the dc microgrid and its proposed protection scheme are implemented in an experimental testbed prototype to verify the fault detection algorithm feasibility. The experimental results indicate that the SDRE scheme can effectively detect faults in a few milliseconds

A Novel Approach for Elimination of Defects of Blocking and Unblocking in Distance Relays during Power Swing

In power systems, distance relays are commonly employed as the primary protection for transmission lines, and their operation is of utmost importance. Power swings are a type of phenomenon that can lead to improper functioning of conventional distance relays, posing a threat to the uninterrupted flow of electrical power. The occurrence of a power swing disrupts the impedance measured by the relay, causing it to deviate from the normal load condition and enter the relay tripping zones. This research paper introduces a novel method based on the Prony method for extracting current waveform components, enabling fault detection during power swings. Subsequently, the proposed method’s accuracy is assessed through simulations implemented on a nine-bus power system, involving three-phase current signal processing and the application of the proposed algorithm. Various fault scenarios encompassing varying fault distances from the relay position, fault resistances, and power angles within the 9-bus system are simulated to encompass a wide range of fault environments. The simulation results demonstrate the effectiveness of the proposed algorithm in detecting all types of faults, including symmetrical and asymmetrical faults, during power swings

OPTIMIZED SWITCH ALLOCATION TO IMPROVE THE RESTORATION ENERGY IN DISTRIBUTION SYSTEMS

In distribution networks switching devices play critical role in energy restoration and improving reliability indices. This paper presents a novel objective function to optimally allocate switches in electric power distribution systems. Identifying the optimized location of the switches is a nonlinear programming problem (NLP). In the proposed objective function a new auxiliary function is used to simplify the calculation of the objective function. The output of the auxiliary function is binary. The genetic algorithm (GA) optimization method is used to solve this optimization problem. The proposed method is applied to a real distribution network and the results reveal that the method is successful. K e y w o r d s: Power distribution systems, switches, restoration energy, genetic algorithm (GA