Voltage Management of Networks with Distributed Generation.

Abstract

At present there is much debate about the impacts and benefits of increasing the amount of generation connected to the low voltage areas of the electricity distribution network. The UK government is under political pressure to diversify energy sources for environmental reasons, for long-term sustainability and to buffer the potential insecurity of uncertain international energy markets. UK Distribution Network Operators (DNOs) are processing large numbers of applications to connect significant amounts of Distributed Generation (DG). DNOs hold statutory responsibility to preserve supply quality and must screen the DG applications for their impact on the network. The DNOs often require network upgrades or DG curtailment, reducing the viability of proposed projects. Many studies exist that identify barriers to the widespread connection of DG. Among them are: suitability of existing protection equipment; rating of existing lines and equipment; impact in terms of expanded voltage envelope and increased harmonic content; conflict with automatic voltage regulating equipment. These barriers can be overcome by expensive upgrades of the distribution network or the expensive deep connection of DG to the higher voltage, sub-transmission network. This work identifies changes in network operating practice that could allow the connection of more DG without costly upgrades. The thesis reported is that adopting options for a more openly managed, actively controlled, distribution network can allow increased DG capacity without upgrades. Simulations have been performed showing DG connected with wind farm production time series to a representative section of the Scottish distribution network. The simulations include modelling of voltage regulation by network equipment and/or new generation. The cost and effects of the consequent network behaviour evaluated in monetary terms are reported. Alternative control strategies are shown and recommended, to reduce DNO operation and maintenance costs and the cost of connection to the developer with no reduction in supply quality.