Two non-overcurrent protection schemes were investigated as part of this project impedance-based protection and transient-based protection. The only credible more » protection solution available in literature for low- fault inverter-dominated microgrids is the differential protection scheme which represents a robust transmission-grade protection solution but at a very high cost. The survey concluded that there is a gap in the available microgrid protection methods. As part of this project a detailed literature survey of existing and proposed microgrid protection schemes were conducted. As a result, overcurrent protection could fail completely to detect faults in inverter-dominated microgrids. Typically, inverters limit their fault contribution in sub-cycle time frame to as low as 1.1 per unit. These microgrids are characterised with limited fault current capacity as a result of current-limiting protection functions of inverters. In this report we address the challenge of designing efficient protection system for inverter- dominated microgrids. The dc microgrid protection design procedure is detailed, and the performance of the proposed method is verified by simulation analysis. Additionally, a trip signal is sent to the corresponding dc circuit breaker (DCCB), to isolate the faulted converter, feeder or a dc bus. These algorithms effectively control the converter pulsewidth and reduce the flow of source current from a particular converter, which helps to increase the fault clearing time. For a high impedance fault, differential comparison method is used to characterize the fault. In this article, an adaptive droop scheme is also proposed to control the fault current by more » calculating a virtual resistance R droop, and to control the converter output reference voltage. Generally, the droop method is used to control the power-sharing between the converters by controlling the reference voltage. For a low impedance fault, the fault current is controlled based on the current/voltage thresholds and current direction. The overcurrent and current directional/differential comparison based protection schemes are incorporated for the dc microgrid fault characterization. The protection scheme is based on the current derivative algorithm. This report presents a novel fault detection, characterization, and fault current control algorithm for a standalone solar-photovoltaic (PV) based dc microgrids. Ultimately, it was identified that more analyses and experimentation are needed to develop optimized fault detection schemes with reduced fault clearing = , A detailed literature review was done to identify possible grounding schemes and protection devices needed to ensure seamless power flow of grid-connected DC microgrids. Therefore, the effectiveness of protection coordination systems with communication were also explored. Due to the absence of physical inertia, the resistive nature of the line impedance affects fault clearing time and system stability during faults. The various parameters that improve the design of protection schemes were identified and discussed. One of the main challenges of DC microgrid protection is the lack of guidelines and standards. This work focused on identifying the types of faults, challenges of protection, different fault detection schemes, and devices pertinent to DC microgrid systems. Successful system protection is critical to the feasibility of the DC microgrid system.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |