Study on Energy Efficiency Improvement Strategies of Photovoltaic-Hybrid Energy Storage DC Microgrids under the Concept of Green Energy Conservation

Abstract

To improve the energy efficiency of a PV-hybrid energy storage DC microgrid, a series of management strategies are proposed in this paper. According to the working principle of photovoltaic cells, the variable step conductance increment method is used to track and control the output power of photovoltaic cells, and the time constant of the low-pass filter is dynamically adjusted according to the output characteristics of supercapacitors in different SOC intervals, so as to put forward a limit management strategy based on the supercapacitor’s SOC partitioning. An energy management strategy for PV DC microgrid based on hybrid energy storage is proposed to address the impact of internal power fluctuation on DC microgrid operation stability. Based on the voltage deviation range, the system is divided into five operation modes to achieve efficient distribution of system power. Through simulation verification, the charging state difference of the battery bank is reduced by 0.00537 after a charging process of 20 s under the withdrawal and addition of PV power, and the charging power ratio is 5.00:8.14:6.82 at steady state under the withdrawal and addition of the hybrid energy storage unit, Udc = 405.4V. This paper’s strategy makes the DC microgrid effective in improving energy efficiency and smoothing out power fluctuations in all operating modes.

Keywords

• photovoltaic-hybrid energy storage
• dc microgrid
• conductivity increment method
• supercapacitor
• mppt control
• 70g10