By Sergio Goncalves

LISBON (Reuters) -Iberia's blackout in April showed that European grids must modernise to cope with more renewable power generation, and Portugal wants the EU to help finance these investments, its energy minister told Reuters on Wednesday.

Energy minister Maria da Graca Carvalho said that unlike in the past, when thermal power plants facilitated grid management with their stable supply, more renewable sources such as wind and solar mean more intermittency and decentralised output which are harder to manage.

"The blackout made it clear there is a need for greater modernisation, digitalisation of the grids, applying data science, storing data, in order to understand what is happening in a more complex system and reacting to it," she said.

"It requires investment and we have been asking the European Commission to guide Europe in this investment and also help co-finance it because it is also a security issue," she said.

The Commission has estimated that to meet its clean energy transition targets, EU countries would need to invest 584 billion euros ($679 billion) to expand and modernise electricity grids by 2030.

In May, it launched a public consultation to receive input for the future European Grids Package, which is expected to be finalised by the end of 2025.

The Spanish government said in a report last week that grid operator Redeia had miscalculated the correct mix of energy in the system on April 28, but also blamed some thermal power plants using coal, gas and nuclear, for failing to help maintain an appropriate voltage level.

A surge in voltage triggered a cascade of power plant disconnections, ultimately leading to the outage that spread to Portugal.

The minister said the report still lacked clarity and Portugal was awaiting an independent report from the European energy regulators' agency ACER to understand what caused the outage and what needs to be done to "avoid future blackouts and, if they occur, to be able to restart (the system) more quickly".

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(Reporting by Sergio Gonçalves; editing by Andrei Khalip and Elaine Hardcastle)