The invention discloses a direct-driven permanent-magnetic 
wind power generation 
system active power 
dynamic control method under a 
voltage drop condition. The method includes the following steps that: grid-connection point 
voltage is acquired, and whether 
voltage drop occurs is judged; when 
voltage drop occurs, an active power automatic adjustment mode is enabled for a 
machine-side converter of a direct-driven permanent-magnetic 
wind power generation 
system, and wind 
turbine variable speed and variable 
pitch control is enabled so that a wind 
turbine can be prevented from entering a speed-limiting protection mode; voltage UGi and power angle theta i outputted by a network-side converter of the direct-driven permanent-magnetic 
wind power generation 
system are acquired, and active power outputted by the network-side converter is calculated; and the active power is adopted to set the active 
power output of the 
machine-side converter, and the active 
power output of the 
machine-side converter is adjusted through adopting a double-
closed loop vector control mode in which a power outer loop and a current 
inner loop are adopted. With the method adopted, direct-current side 
overvoltage caused by energy accumulation at a direct-current side when rid-connection point voltage drops in a wind power 
plant can be avoided, and wind curtailment of a 
wind field can be decreased. The method has the advantages of fast 
response time, low implementation cost as well as being simple and reliable.