ABSTRACT

In recent decades, the advances in distributed renewable generation technology and environmental considerations have significantly reshaped the structure of power generation, transmission, and distribution. There is an increasing penetration of various forms of renewable energy sources (e.g., wind turbines, combined heat and power [CHP], and solar energy) in current medium-voltage power distribution grids. The UK government aims to provide 15% of national electricity supplies based on renewable energy by 2020, implying about 21 GW of generation from current medium-voltage distribution grids (e.g., 33 and 11 kV). Distributed generation is an approach that adopts small-scale technologies to produce electricity close to the end users of power. It can be defined as a variety of electrical power sources and technologies with limited capacity that can be directly connected to the distribution network and consumed by the end users. Distributed generators (DGs) may come from renewable sources like small-scale wind turbines, photovoltaic (PV) panels, micro-hydro systems, fuel cells, and biomass. Conventional DGs may include micro gas turbines, diesel engines, sterling engines, and internal combustion reciprocating engines. In many cases, DGs can provide lower-cost electricity and higher power reliability and security, with fewer environmental consequences, than traditional power generators. The DGs can generate the power and supply the customers locally without a long-distance power transmission and distribution process, which can effectively reduce the peak demand and minimize the network congestion from the centralized power utilities, as well as yield additional revenue (Lopes et al., 2007). However, it is known that a massive DG integration in medium- and low-voltage levels can introduce tremendous challenges, mainly due to the intermittent generation of renewable sources and limited available network monitoring and control functionalities. As a result, the distribution grid is no longer a passive system, but an active system interconnecting power generators and loads with bidirectional power flows and complex operational phenomena, for example, voltage rise effect, increased fault level, protection degradation, and altered transient stability (Lopes et al., 2007; Maurhoff, 2000). Most of the current distribution networks are managed via a centralized control at a control center of a distribution network operator (DNO) relying on supervisory control and data acquisition (SCADA) systems designed for the purpose of simple network operations. Due to the large geographical scale of distribution grids and the increasing population of DGs, such overall central control becomes inefficient, and even not practical. Therefore, a novel active network management (ANM) solution is required to maximize the DG connection capacity with acceptable cost penalties.