An improved max-min ant system (MMAS) algorithm is presented for optimal siting and sizing of distributed generators (DGs) in a microgrid. The strategies of the optimization are to maximize the economic benefit and to guarantee stipulated reliability criteria. Firstly

a multi-objective model for configuration of the independent microgrid

which includes wind power

photovoltaic (PV) generation and energy storage devices in different environments

is developed. The rate of load power supply after a failure is defined. Meanwhile

the related factors

such as the energy excess rate

the steady rate of load power supply and DGs’ constraints in the microgrid

are considered. Secondly

an improved MMAS algorithm is proposed to improve the rate and precision of convergence by adaptively adjusting the information heuristic factor and expectation heuristic factor. Then

the flow chart of optimally siting and sizing of DGs is designed. Through an evaluation of economy and reliability during a specified period of time

a comprehensive approach is obtained. Finally

the optimization is programmed in MATLAB to achieve the optimal sizing of a five-bus island system and the optimal siting of the medium voltage microgrid on an island of Denmark. The advancement and feasibility of the improved algorithm are validated through comparison of relevant cases. This work is supported by National Natural Science Foundation of China (No. 51147010

No. 51107120).