From Blackout towards a 'Smart Grid' - Prospects of Power System Developments

摘要

The growth and extension of AC systems and consequently the introduction of higher voltage levels have been driven by a fast growth of power demand over decades. Power systems have been extended by applying interconnections to the neighbouring systems in order to achieve technical and economical advantages. Regional systems have been extended to national grids and later to interconnected systems with the neighbouring countries. Large systems came into existence, covering parts of or even whole continents, to gain the well known advantages, e.g. the possibility to use larger and more economical power plants, reduction in reserve capacity in the systems, utilisation of the most efficient energy resources, as well as to achieve an increase in system reliability. Global studies show that power consumption in the world follows the increase in population closely. In the next 20 years power demand in developing and emerging countries is expected to increase by more than 250%, in industrialised countries, however, only by 37% (Global Insight 2008, Siemens Energy 2008). In future, in the course of deregulation and privatisation, the loading of existing power systems will strongly increase, leading to bottlenecks and reliability problems. System enhancement will be essential to balance the load flow and to get more power out of the existing grid in total. Large blackouts in America and Europe confirmed clearly that the favourable close electrical coupling of the neighbouring systems might also include the risk of uncontrollable cascading effects in large and heavily loaded interconnected systems. An overview of the sequence of blackout events in US/Canada and Europe is given and countermeasures for blackout prevention - "Lessons learned" - are discussed. Avoidance of loop flows, prevention of voltage collapse, elimination of stability problems in large power systems as well as the implementation of "firewalls" are presented. The benefits of HVDC (High Voltage Direct Current) and FACTS (Flexible AC Transmission Systems) for system enhancement are explained.