Note 2 - Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues	$ 21,117	$ 14,012	$ 42,329	$ 27,782
Grid [Member]
Revenues	16,347	11,489	34,062	21,345
Grid [Member] | Americas [Member]
Revenues	15,677	10,698	26,231	18,499
Grid [Member] | Asia Pacific [Member]
Revenues	370	393	6,385	2,220
Grid [Member] | EMEA [Member]
Revenues	300	398	1,446	626
Wind [Member]
Revenues	4,770	2,523	8,267	6,437
Wind [Member] | Americas [Member]
Revenues	30	1	42	47
Wind [Member] | Asia Pacific [Member]
Revenues	4,734	2,464	8,002	6,320
Wind [Member] | EMEA [Member]
Revenues	6	58	223	70
Equipment and Systems [Member] | Grid [Member]
Revenues	15,261	10,044	31,798	18,399
Equipment and Systems [Member] | Wind [Member]
Revenues	4,059	2,077	6,676	5,581
Services and Technology Development [Member] | Grid [Member]
Revenues	1,086	1,445	2,264	2,946
Services and Technology Development [Member] | Wind [Member]
Revenues	$ 711	$ 446	$ 1,591	$ 856