Security constrained dynamic economic dispatch (DED) is a complex non-linear constrained optimization problem in power system operation and control. The main objective of security constrained DED problem is to determine the optimal power generation schedule for the online generating units over a time horizon at the same time satisfying the transmission and generation constraints. This paper proposes an efficient chaotic differential harmony search (CDHS) algorithm to solve the security constrained DED problem. In the proposed algorithm, chaotic variables are introduced instead of random number generator in the differential mutation operator of differential harmony search (DHS) algorithm to accelerate the DHS algorithm to reach the global optimal solution quickly. The effectiveness of the proposed CDHS algorithm is demonstrated on IEEE-30 bus system with valve point effects, ramp rate limits, prohibited operating zones, transmission line flow and bus voltage limits constraints for a period of 24 hours. The simulation results obtained by the proposed CDHS algorithm are compared with DHS algorithm. The optimal solutions obtained by the proposed algorithm are better than DHS algorithm in terms of solution quality, speed of convergence and computational time. © 2013 IEEE.