**Ming Yu, Junguo Zhang \* and Hanxing Liu**

School of Technology, Beijing Forestry University, Beijing 100083, China; yuming@bjfu.edu.cn (M.Y.); liuhanxing@bjfu.edu.cn (H.L.)

**\*** Correspondence: zhangjunguo@bjfu.edu.cn; Tel.: +86-10-6233-6398

Received: 6 June 2019; Accepted: 19 June 2019; Published: 20 June 2019

**Featured Application: The improved control method using complementary energy storage units can enhance the transient stability and operation reliability of microgrids in forests, providing theoretical support for the construction of forest microgrids.**

**Abstract:** In order to improve the power quality and the fault ride-through capability of islanded forest microgrids, a hybrid complementary energy storage control method is proposed. In this method, mode-based sectional coordinated control is adopted as the basic control scheme, whereas control of the hybrid energy storage, which includes the battery, the supercapacitor, and the wind turbine, utilizes the improved strategy. According to the characteristics of the energy storage units, adaptive control of batteries and supercapacitors are adopted to smooth the low-frequency power fluctuation in the long-term and to suppress the high-frequency component separately, in which predictive control of the converters is utilized to achieve rapid regulation. Furthermore, as a third energy storage unit, the wind power unit was investigated, utilizing the large rotating kinetic energy of the wind turbine to temporally suppress huge power disturbance and avoid load shedding. To verify the effectiveness of the proposed coordination control with hybrid complementary energy storage, simulations of the islanded DC microgrid in forest area were conducted in MATLAB/Simulink, with the results showing that, by utilizing the improved control method, the transient operation characteristics of the system were effectively enhanced.

**Keywords:** forest microgrid; biomass energy; operation mode-based sectional coordinated control; hybrid energy storage; predictive control; inertia improvement
