Control and Protection of Power Electronics Interfaced Distributed Generation Systems in a Customer-Driven Microgrid

This paper discusses control and protection of power electronics interfaced distributed generation (DG) systems in a customer-driven microgrid (CDM). Particularly, the following topics will be addressed: microgrid system configurations and features, DG interfacing converter topologies and control, power flow control in grid-connected operation, islanding detection, autonomous islanding operation with load shedding and load demand sharing among DG units, and system/DG protection. Most of the above mentioned control and protection issues should be embedded into the DG interfacing converter control scheme. Some case study results are also shown in this paper to further illustrate the above mentioned issues.

Distributed generation (DG) is becoming an increasingly attractive approach to reduce greenhouse gas emissions, to improve power system efficiency and reliability, and to relieve today’s stress on power transmission and distribution infrastructure. In recent years, DG systems based on renewable energy source (RES) or micro-sources such as fuel cells, photovoltaic (PV) cells, wind turbines, and micro-turbines are experiencing a rapid development, due to their high efficiencies and low (or zero) emissions. The micro-source based DG also presents a challenge in terms of interaction to the grid, where the power electronic technology plays a vital role [1, 2]. The development of DG has lead to a more recent concept called microgrid [3], which is a systematic organization of DG systems. Compared to a single DG, a microgrid has more capacity and control flexibilities to fulfill system reliability and power quality requirements. The microgrid also offers opportunities for optimizing DG systems. A typical example is the combined heat and power (CHP) generation or cogeneration, which is currently the most important measure to improve energy efficiency. For the CHP applications, the heat producing generation units and non-heat producing units in the microgrid can be optimally placed with the siting flexibilities of DG units [4]. Furthermore, the microgrid can operate in gridconnected mode or autonomous islanding mode and benefit both the utility and the customers.

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