Distributed Consensus-Based Optimization of Multiple Load Aggregators for Secondary Frequency Control

Responsive loads can act as spinning reserve which is incorporated with the conventional AGC units for the improvement of frequency reliability. In this paper, a distributed consensus-based optimal strategy of responsive load aggregators and AGC units is presented to provide secondary frequency control in the power system. Specifically, two-step optimal model is proposed. In the first step, Lambda-Iteration method is used to yield the total active power command for load group and AGC group. In the second step, the distributed optimal algorithm with -logarithmic barrier cost function is proposed to allocate the active power command to multiple load aggregators and AGC units while guaranteeing consensus among individual incremental costs. In achievement of such a consensus, two virtual pinners are utilized to generate the regulation signal only shared with a part of load aggregators and AGC units, respectively. Moreover, the communication topology among load aggregators is a strongly connected digraph, the same as to the AGC units. Finally, simulation results show that the system frequency can be greatly improved, while the total cost of the whole system can be minimized with both equality and inequality constraints.