Research on the protection coordination of permanent magnet synchronous generator based wind farms with low voltage ride through capability

Protection and Control of Modern Power Systems

Table 1 Comparison between the conventional protection and improved protection

Protection		Without LVRT		LVRT
Protection		Settings	Time(s)	Settings(U_N)	Time(s)
Voltage violation protection	Upper limit protection	1.15U_N	0 s	1.15U_N	0
	Upper limit protection	1.10U_N	0.1	1.10U_N	2
	Lower limit protection	0.9U_N	0.1	0.9U_N	2.2
				0.5U_N	1.3
				0.2U_N	0.66
Frequency protection	Upper limit protection	50.5Hz	0.1	52.5Hz	2
Frequency protection	Lower limit protection	49.5Hz	0.1	47.5Hz	2
Over current protection	Primary section	Phase to phase fault	0	NO
Over current protection	Zone III	2I_N	1.5	NO
Voltage unbalance protection	0.1U_N		0.3	0.1U_N	3
Current unbalance protection	0.15I_N		0.1	0.15I_N	1