Double-fed asynchronous motor-generator equipped with a 3-level VSI cascade

Abstract

In a concern for sustainable development, the rational use of electrical energy implies having transportation networks capable of transmitting large quantities of electrical energy over long distances as well as adequate storage plants. This double requirement is the consequence of the fact that electrical energy has to be produced and consumed simultaneously, as direct storage of large quantities is not economically feasible. Nowadays, as thermal power plants and runoff river plants are always working at their nominal power for economic reasons; it is not possible to cover the large space and time demand variations without having an efficient transportation network and adequate storage capacities. The recent start up of major windformer sites also implies the need for supplementary storage capacities. The inventory of large storage plants reveals the solution "pump-storage plant" as being one of the best in terms of storage potential, flexibility, reliability, response time, efficiency, risks and costs. Nearly all the pump-turbine groups operating today consist of synchronous motorgenerators working at the network frequency and therefore at constant speed. The performance and efficiency of such groups can be significantly improved by using variable speed motor-generators, and more specifically doubly-fed asynchronous motor-generators. The few variable speed units in operation today are equipped with a cyclo-converter cascade. The purpose of the present thesis is to propose the replacement of the cycloconverter solution by a back to back 3-level VSI cascade and investigate the complete regulation strategy.

Stability study of a mixed islanded power network

“…The main parameters of the wind turbine model are Table II. More details about the DFIG architecture can be found in [14]. The chosen control strategy optImIzes the conversion of power by using a look-up table def ning the optimal turbine speed nset and the optimal pitch angle Bp,set, set according to the wind velocity.…”

Advanced Vector Control Design for DFIM-Based Hydropower Storage for Fault Ride-Through Enhancement

“…Moreover, some authors have presented practical results of the installed PSH units in Ohkawachi and Goldisthal power station located in Japan [5] and Germany [6], respectively. However, the cycloconverter used in the mentioned plants is substituted with the state-of-the-art multilevel inverters using the integrated gate-commutated thyristor (IGCT) in [7]. Additionally, some studies, such as those found in [8] and [9], have only a general view on the ASPSH, and they do not assist to design its advanced controller.…”

Start-up of a varspeed group in pump mode, practical implementations and tests

“…The details of the behavior of the transformer part are outside of the scope of this paper. For further explanations and details refer to [12].…”