Low Voltage Micro-power Grid Operation Control Research Of Desert Irrigation System

The paper is supported by scientific and technological support projects in Xinjiang,and contents of this paper is low voltage micro-grid which used in road green belt irrigation system for preventing desertification. First of all, according to the structural characteristics of micro power grid, choosing easy to control and running stability of the hybrid bus low-voltage power grid, and analyzes each unit structure principle of the system. On the basis of the residual capacity calculation formula of the system, and when the system in grid mode, the remaining storage capacity(SOC) is normal, studying the maximum power tracking problem in PV system. The traditional fixed step size perturbation observation in the sudden changes of sunshine intensity will produce fluctuations in the maximum power point, then into the blind area. So this paper proposes a small amount of computation variable step disturbance observation, and set the voltage threshold,by simulation can prove the tracking strategy could satisfy both rapidity and stability. Secondly, the paper studied the pre-synchronization control to reduce impact of the grid-connected to achieve soft cut, as well as constant power control applications. Finally, when the remaining storage capacity unusual, AC bus of the system by the grid clamp, DC bus voltage and stability control of the system have become the core of the problem. In this paper, proposing two improvement strategies of inverter: The first is aimed at the traditional single current feedback strategy, introduces the second differential part in the strategy for controlling three-phase inverter. The strategy can obtain small harmonics current and good waveform, when increasing the system damping, power consumption and size of the inverter system are smaller at the same time. The second method is to improve the two-loop control, the outer ring is the grid current loop, the inner loop is the capacitor current, with double PI controller, finding the system stability condition by Rolls criterion. The simulation shows that the system can not only get a good wave, low steady-state error, high power factor and fast response, but also effectively suppress current resonance peak issue of the LCL filter.