The phrase "series of crises" is correct and can be used in written English.
You could use it in a sentence such as, "The country experienced a series of crises in the wake of the economic downturn."
Germany's reunification brought a series of crises for Wolf.
A series of crises forced Saud to abdicate in 1964.
Emerging markets have endured a series of crises since the Latin American default of 1982.
In the late 1830s, they faced a series of crises that stretched them to the limit.
Beginning in the summer of 2000, however, Barak faced a series of crises.
The insurance fund has taken over 19 banks since 1997, after a series of crises.
Still, there's no doubt Love kept the group together through a series of crises.
Thus begins the series of crises, domestic and existential, that keep "Morning's at Seven" percolating.
And, with a series of crises around the world increasingly coming to dominate Obama's Presidency, it can hardly be overlooked.
He has stuck to that strategy even as events have conspired to focus attention on a series of crises.
Brand BBC has been blighted by a series of crises recently, though none so heinous as the Savile scandal.
