Research on Operation Control of Low-Voltage Microgrids for Irrigation Systems in Xinjiang's Desert-Gobi Regions

This study focuses on developing a low-voltage microgrid irrigation system for road green belts and sand prevention based on the sustainable development of Xinjiang. Under grid-connected mode, when the remaining capacity of the energy storage system is at a normal level, the maximum power point tracking (MPPT) issue of the photovoltaic power generation system becomes particularly critical. Building on traditional disturbance observation methods, this paper proposes a variable step-size disturbance observation method with reduced computational requirements. Simulation results confirm that this tracking strategy meets the requirements for both speed and stability. However, in cases where the remaining capacity of the energy storage system is abnormal, the alternating current (AC) bus is constrained by the grid, making, the direct current (DC) bus voltage and system stability control the core challenges. To address this issue, two inverter improvement strategies are proposed: The first strategy introduces a secondary differential link based on traditional single current feedback control to manage the three-phase grid-connected inverter. This method not only achieves minimal current harmonics and good waveform quality but also increases the system damping coefficient while reducing power loss and size of the inverter system. The second strategy improves dual-loop control, where the outer loop is the grid-connected current loop and the inner loop is the capacitor current loop, using dual PI controllers. The stability conditions of the system are determined through the Routh criterion, and simulation results show that the system can achieve good waveform quality, low steady-state error, high power factor, and rapid response, effectively suppressing current resonance peaks caused by LCL filters. Finally, this paper explores presynchronous control techniques to reduce inverter grid connection impacts, achieving soft grid connection and constant power control applications. This study plays a positive role in promoting the development and utilization of sandy desert areas in Xinjiang, and provides guidance for theoretical research and engineering practice.